The Evolutionary Psychology of Jealousy in Romantic Relationships: Evidence for a Sexually Dimorphic Response Mechanism in Humans by REBECCA M. ALLEN A thesis submitted in partial fulfillment of the requirements for the Degree of Bachelor of Arts with Honors in Psychology WILLIAMS COLLEGE Williamstown, Massachusetts May 11,2005 Abstract Evolutionary psychologists have proposed that men and women differ in their relative responses to sexual vs. emotional infidelity in a romantic relationship, a proposal based upon the presumption of evolved sex differences in mating strategies. Because sexual infidelity signals the possibility of being cuckolded and emotional infidelity signals the possible withdrawal of resources, men are expected to be relatively more jealous over the former whereas women are expected to be relatively more jealous over the latter. Although past research has demonstrated robust support for the evolutionary hypothesis, this support has been called into question on both empirical and conceptual grounds. In this thesis, I test the claims of the evolutionary hypothesis using a novel experimental paradigm designed to address previous methodological concerns. In two studies, participants (college students in Study 1; married adults in Study 2) were asked to consider a series of hypothetical scenarios depicting cues to either sexual or emotional infidelity and to rate their responses on a variety of continuous measures. Across both studies, as expected, women were found to be significantly more bothered by emotional cues than were men. Contrary to expectations, however, women and men displayed similar responses to sexual cues, with women having a slight tendency to be more bothered than men. The latter effect was less consistent than the former, however, giving rise to a reliable two-way interaction between sex and infidelity type (sexual vs. emotional). Although these findings were only partly supportive of my predictions, they nonetheless demonstrate that humans do display a sexually dimorphic jealousy response, and provide support for the contention that this is an evolved mechanism. Discussion addresses a number of additional findings, as well as avenues for future research. Contents I. Introduction................................................................................... 4 I1 . Study 1 ....................................................................................... 30 -Method ............................................................................ 34 -Results............................................................................38 -Discussion....................................................................... -44 I11 . Study 2 ....................................................................................... 48 -Method ............................................................................ 49 -Results............................................................................ 50 -Discussion........................................................................ 54 IV. General Discussion ....................................................................... -59 V. References................................................................................... 66 VI. Acknowledgements........................................................................71 VII. Appendix................................................................................... -72 VIII. Tables and Figures .........................................................................82 The Evolutionary Psychology of Jealousy in Romantic Relationships: Evidence for a Sexually Dimorphic Response Mechanism in Humans "O! beware, my lord, of jealousy; It is the green-eyed monster which doth mock The meat it feeds on."-William Shakespeare, Othello Anyone who has ever been in a romantic relationship probably has a firsthand understanding of the emotional distress that any threat to this relationship may cause. The very suspicion that one's mate may be romantically interested in a rival is enough to inspire a negative reaction in anyone, such as sadness, insecurity, hurt feelings, or anger -in some cases, even enough anger to attack one's partner or the object of their affection (Daly & Wilson, 1988). All of these negative feelings that arise in response to a romantic partner's past or imminent infidelity can be commonly understood as manifestations of jealousy. Jealousy over romantic relationships is a universal phenomenon that can be seen in men and women across cultures and age groups (Buunk, Angleitner, Oubaid & Buss, 1996; Buss, Shackelford, Kirkpatrick, Choe, Lim, Hasegawa, Hasegawa & Bennett, 1999; Wiederman & Kendall, 1999; Harris, 2003). Evolutionary theorists have proposed that jealousy is a response mechanism that has been naturally selected for in humans because over the course of evolution, those who had a negative response to signs of a mate's infidelity would be more apt to prevent this infidelity and thus experience higher rates of reproductive success (Wiederman & Allgeier, 1993). This explanation appears likely when we consider the fact that many other animals have also evolved mechanisms to reduce the possibility that their mate will engage in extradyadic copulation. For example, among Plecia nearcticas, aptly laown as "love bugs," after a male gains access to a sexually receptive female he remains attached to her in a copulatory embrace that can last for days, thereby preventing other males from fertilizing her eggs. Another species of insect, Johannseniella nitida, adopts an even more drastic strategy: Males of that species actually leave their genitalia behind, broken off inside the female, after insemination -presumably to seal off the female's reproductive opening and thus forestall takeovers from rival males (Buss, 2003). Considering the fact that even lowly insects have evolved specialized behaviors to prevent the likelihood of losing their mate to a rival, it is reasonable to surmise that humans have also evolved an innate sense of jealousy to accomplish the same purpose. However, a specific aspect of the evolutionary theory of jealousy that has come under intense scrutiny is the hypothesis that humans have evolved sexually dimorphic jealousy mechanisms that cause males and females to be differentially upset by different types of infidelity. Specifically, this theory postulates that men will be relatively more jealous about their mate's sexual straying, whereas women will be relatively more jealous at the prospect of their mate's emotional involvement with a rival (Buss, Larsen, Westen & Semmelroth, 1992). A great deal of research has been done to investigate this question, and while considerable support has been found for the hypothesis, there is much debate in the field over whether jealousy is really an evolved sexually dimorphic mechanism, or if gender differences in jealousy can be explained by other, more social or cultural influences (Harris, 2003). The goal of this thesis is to offer an unbiased examination of the arguments for and against the evoXutionary theory of human jealousy and to build on previous studies by developing and implementing an experimental paradigm that addresses the limitations of these studies. I ultimately intend to determine a) whether there really is a sex difference in jealousy response to different types of infidelity, and b) if so, whether this difference can be attributed to evolved mechanisms or a more socially learned explanation. Understanding the Evolutionavy Argument Human males and females, over the course of evolutionary history, have undoubtedly faced differing environmelltal pressures and circumstances affecting mating behavior. Some of the effects of these pressures can be seen in the sex-differentiated psychological tendencies and preferences shown by men and women -for instance, countless studies have demonstrated that men worldwide tend to be attracted to women with physical attributes of youth and fertility, which indicate an ability to bear healthy children, whereas women are more attracted to signs of social dominance and material wealth, which are cues to a man's ability to provide resources for her offspring (e.g. Buss, 1989; Kenrick & Keefe, 1992). Attraction to certain characteristics in the opposite sex is not the only way that past evolutionary pressures might manifest themselves in human psychology; in order to preserve their chances of reproductive success, males and females may have also needed to be sensitive to different types of cues that could indicate a potential threat to their mating relationship. This idea is where the evolutionary theory of jealousy has its origin. For any species of animal that employs internal fertilization, the males are faced with a reproductive dilemma: It is impossible for a male to be certain that his mate's offspring are the result of his own fertilization or a competitor's. Different species have evolved different methods of countering this uncertainty of paternity, from mate-guarding behaviors to infanticide to simply impregnating as many females as possible (Buss 8& Shackelford, 1997; Buss, 2003). As humans are a relatively monogamous species, meaning that a man's investment of time and resources in his mate tends to be high, it would be especially costly to him if his mate were sexually unfaithful, because all of his energy would be devoted towards raising offspring that did not carry his own genes. Thus it follows that over the course of evolution, human males who were sensitive to indications of their mate's sexual straying such that they could minimize or forestall it altogether would have been more successful at passing down their genes than males who were not bothered when their mate showed signs of sexual interest in another man. Females, on the other hand, can be 100% certain that their offspring carries their own genes, so this should not have been a primary concern for them. However, since the female was the one who bore and consequently raised her children, she would have had a much higher probability of success if she could be certain that her mate remained emotionally devoted to her, providing his material support and protection for the extended time that it takes to raise a child to adulthood. A man's brief sexual dalliance, although potentially troubling, would not have been harmful to his mate's reproductive success so long as he stayed emotionally attached and willing to share his resources with her. Women who were vigilant to signs that their mate's affection (and hence his resources) was being diverted to another, such that they could minimize or forestall this occurrence, therefore should have held an evolutionary advantage over those who were oblivious to these indications of emotional interest and attention towards a competitor. From the logic of these scenarios comes the evolutionary theory ofjealousy: Although members of both sexes should be upset by any type of infidelity on the part of their mate since emotional and sexual infidelity frequently co-occur (Harris & Chistenfeld, 1996; DeSteno & Salovey, 1996), men are predicted to be relatively more upset by sexual infidelity than women, and women are expected to be relatively more upset by emotional infidelity than men (Buss et al., 1992). The idea of increased male sexual jealousy has been supported with statistics on morbid jealousy, spousal abuse, and homicide in response to sexual infidelity, all of which are more commonly found in men than women (Daly & Wilson, 1988). Additionally, it has been found that women place a much higher importance on emotional investment in a relationship than men do; a man's ability to commit is a key factor in a woman's assessment of his potential as a mate, and women who repeatedly engaged in sex without a high degree of emotional investment were found to have heightened levels of anxiety and distress despite holding the "liberal" opinion that uncommitted sex was morally acceptable (Townsend, 1995). In another study, when 15 committed undergraduate couples were asked to list as many jealousy evoking situations as they could think of, men were significantly more likely to list sexual scenarios, whereas women tended to list situations in which their partner spent more time with or showed emotional attachment to a potential rival (Francis, 1977, as cited in Wiederman & Allgeier, 1993). Despite the fact that these and many other studies appear to support the evolutionary hypothesis, we must be cautious in our interpretation of the data. Men do commit more violent crimes than women in response to sexual infidelity, but this may simply be a reflection of the fact that men commit more violent crimes overall than women do. Also, as Harris points out in her 2003 review, people who are morbidly jealous or who commit murder as a reaction to jealousy represent extreme, possibly mentally unstable cases, and "observations about population extremes are likely to offer a very unreliable guide to species-typical characteristics" (p. 108). In the case of the undergraduate couples listing the predicted types of scenarios that would make them jealous, this could just be because men tend to think about sex in general more than women do, and women tend to think more about emotional issues, so these were the exemplars that happened to spring to mind. Obviously, one cannot rely on homicide statistics or general jealousy studies as proof of the evolutionary hypothesis -in order to truly examine its worth, we must turn to studies that have been specifically designed to test the question of whether the sexes differ in their sensitivity to infidelity, as predicted by evolutionary theory. Robust Support for the Evolutionary Theory One groundbreaking study performed by Buss and his colleagues in 1992 provided direct support for the evolutionary theory of jealousy. In a simple experimental design, Buss presented participants with two hypothetical scenarios. Participants were asked to imagine that their romantic partner either formed a "deep emotional attachment" to or had "passionate sexual intercourse"with another person, and were then asked to choose which of the two would upset or distress them more. An additional set of questions asked whether their partner "trying different sexual positions" or "falling in love" with another person would upset them more. The results fiom this simple, forced- choice measure were as predicted by the evolutionary hypothesis: Significantly more men than women chose the instance of sexual infidelity as more upsetting, for both sets of scenarios. In this same study, Buss also found preliminary physiological evidence in support of the hypothesis, reporting that men showed more electrodema1 activity (EDA) and a higher pulse rate (PR) when imagining sexual infidelity than emotional infidelity, whereas women displayed the opposite tendencies (Buss et al., 1992). These findings in support of the evolutionary theory ofjealousy have been replicated by many subsequent studies employing the same or similar forced-choice methodology (Wiederman & Allgeier, 1993; Buunk et al., 1996; DeSteno & Salovey, 1996; Wiederman & Kendall, 1999; Buss et al., 1999; Cramer, Abraham, Johnson, & Manning-Ryan, 2001; DeSteno, Bartlett, Braverman, & Salovey, 2002; Harris, 2002; Pietrzak, Laird, Stevens & Thompson, 2002; and for a meta-analysis, see Harris, 2003). Different populations have been sampled, different cultures have been tested, and the phrasing of the scenarios has been altered slightly, but across them all, one very robust effect is that when people are asked to choose between the two different types of infidelity, significantly more men than women indicate that sexual infidelity is worse, and significantly more women than men choose emotional infidelity as worse. The reliability of this finding is undeniable, even in samples from cultures as diverse as Germany, the Netherlands, Sweden, Japan, and Korea (Buunk et al., 1996; Wiederman & Kendall, 1999; Buss et al., 1999). Similar results have also been found when asking men and women which type of infidelity they would be more likely to forgive, and which would lead them to break up with their partner (Shackelford, Buss, & Bennett, 2002). But the support for the evolutionary hypothesis isn't as clear-cut as it might first appear. One finding that throws a snag into the evolutionary argument is the fact that, though the percentage of men who are more upset by sexual infidelity is significantly higher than the percentage of women who are, that number is still frequently lower than 50%. This means that the majority of men in many samples chose emotional infidelity as more upsetting than sexual, even though the evolutionary theory seems to predict that this should not be the case. Also, the variability of the percentages of men and women who are more upset by one type of infidelity vs. the other across samples is disconcertingly high. For instance, in one cross-cultural study, 76% of the American male sample were more upset by the sexual than the emotional scenario, whereas only 38% of the Japanese male sample were (Buss et al., 1999). Obviously, culture and other factors do have a substantial effect on which scenario a person is more likely to pick, and evolutionary theorists are quick to point out that evolution does not give rise to "hard-wired," inflexible tendencies, but rather predispositions that are subject to variation according to cultural and situational variables (Wiederrnan & Allgeier, 1993). Moreover, the crucial fact remains that in both of those samples, as well as in all of the other studies, the percentage of the female equivalent that chose sexual infidelity as more distressing was still significantly lower than the percentage of males who did. The key argument put forth by the proponents of evolutionary theory is for a sex difference in jealousy, and this sex difference is indisputably robust across virtually all studies replicating Buss's original forced-choice method. The Double-Shot Hypothesis: An Alternative Explanation Though most researchers, using Buss's methodology, have had no trouble replicating his findings of a significant sex difference in what type of infidelity maltes people more jealous, there has been significant controversy over how those findings should be interpreted. A few psychologists, such as David DeSteno and Christine Harris, have proposed alternative, non-evolutionary explanations for these results, explanations that make sense of the findings not by appealing to domain-specific evolved tendencies but to more domain-general human reasoning ability. The most well-known name for this cognitive interpretation of Buss's data is the "double-shot hypothesis."This hypothesis asserts that men and women will be more upset about the type of infidelity that they believe is most likely to imply that the other type of infidelity is occurring as well (DeSteno & Salovey, 1996). In other words, women will be especially jealous about emotional infidelity because they believe that if a man is in love with someone he is likely to be having sex with her (i.e. emotional and sexual infidelity), whereas it is probable that a man will willingly have sex with someone without being in love with her, (i.e. sexual without emotional infidelity). Conversely, according to this hypothesis, men believe that it is possible for a woman to be emotionally attached to someone without having sex, but if she is having sex with someone then she is probably also in love with him (see Harris & Christenfeld, 1996, for a similar argument). Thus, regarding Buss's results, it appears as though gender is the variable that affects jealousy, when in reality it is individuals' rational beliefs about the opposite sex that cause them to show a sex- differentiated response. In order to test this theory, a differential infidelity implication (DII) scale was created by subtracting a participant's likelihood judgment that sexual infidelity would also imply emotional infidelity from their judgment that emotional infidelity would also imply sexual infidelity (DeSteno & Salovey, 1996). Thus, a positive DII would indicate that the participant believed that emotional infidelity implies sexual infidelity more than the other way around (expected for women), a negative DII would indicate the opposite (expected for men), and a DII around zero would mean that the participant believed that the two types of infidelity implied each other equally. The first study using this scale found that, although sex initially did predict jealousy reactions, this effect was rendered nonsignificant when DII was calculated and controlled for statistically. A participant's DII could significantly predict which type of infidelity he or she would choose as worse -women tended to have a positive DII, with a majority choosing emotional infidelity as worse, and men's ID11 hovered around zero, with 49% choosing sexual as worse (DeSteno & Salovey, 1996). Another more recent study with a homosexual sample also found support for the double-shot hypothesis using the DII scale -overall, jealousy seemed to be more influenced by the sex of the unfaithful partner than by the sex of the subject (Dijkstra, Groothof, Poel, Laverman, Schrier, & Buunk, 2001). Evolutionary Response to the Double-Shot Argument Proponents of the evolutionary theory of jealousy have put forth two main arguments in response to the challenge of the double-shot hypothesis. First, they argue that the double-shot hypothesis is incomplete in that it doesn't provide an account as to why men and women across cultures would have these sex differences in beliefs about infidelity (Buss, Larsen, & Weston, 1996; Buss et al., 1999; Shackelford et al., 2002). It is possible that these beliefs could be a result of differential socialization rather than evolutionary pressures, but then why would all boys across cultures be taught to believe that women were more likely to have sex only when they were already in love and vice versa for girls? The evolutionary account provides an explanation for this, which is that women must consider a man's willingness to commit to her and her children before she will mate with him, whereas men are under no such evolutionary obligation and thus find sex without emotional attachment much more palatable. Social-cognitive accounts such as the double-shot hypothesis cannot offer a parsimonious explanation for why people's rational beliefs about infidelity would be so similar around the world. Second, the DII scale used by DeSteno and his colleagues as evidence against the evolutionary hypothesis may be misleading. Taking a factor that correlates highly with sex, such as beliefs about infidelity, and examining its relationship to different jealousy reactions does not prove a causal relationship. As Buss points out, one might perform the same statistical procedure with such sex-related factors as height or testosterone levels and come to the erroneous conclusion that those were in fact what caused the demonstrated sex difference in jealousy (Buss et al, 1996). A simpler and more effective way to test the validity of the double-shot hypothesis would be to repeat the forced-choice self-report methodology, but to use scenarios that either specified that each type of infidelity was exclusive of the other, or scenarios in which both types of infidelity occurred and participants were asked which aspect of the infidelity upset them the most. Both of these suggestions were tested in subsequent studies, and the results in general did not bode well for the double-shot hypothesis. When participants were asked to choose whether sexual without emotional infidelity or emotional without sexual infidelity was worse, and when participants were presented with a scenario of both sexual and emotional infidelity and asked which aspect was worse, in all situations the predictions of the evolutionary hypothesis were borne out. Men still chose sexual infidelity as the most upsetting more often than women did, and vice versa (Buss et al., 1999; Cramer et al., 2001). When DII was calculated in these studies, using the same methodology that DeSteno used, mixed results were found: in one sample, DII alone was a significant predictor of jealousy but when it was combined with sex it lost its significance (Buss et al., 1999), and in another sample, DII was not statistically reliable for men and marginally significant for women, but in the direction opposite from what the double-shot would predict (Cramer et al., 2001). Clearly, results using the DII scale are mixed and inconclusive at best, and findings from subsequent studies designed to separate emotional from sexual infidelity more distinctly have found a sex difference that cannot be explained by the double-shot hypothesis. Alternative Methods of Measurement The data that have been discussed up to this point can for the most part be characterized as generally supportive of the evolutionary theory of jealousy, with a few questions left unanswered (such as why, in some samples, the majority of men were more upset by emotional infidelity, and to what extent variables like culture and beliefs can affect evolved jealousy tendencies). However, there is one crucial limitation that applies to all of the studies that have been discussed thus far: they have all employed the same, simple, forced-choice, self-report methodology to measure jealousy. Though this method does have its strengths, it also has significant limitations, one of which being that forced- choice scenarios are extremely artificial. In everyday life, no one could ever actually choose whether they would prefer their mate to have an exclusively sexual affair or an exclusively emotional one. This may mean that the forced-choice methodology is a poor measure of actual human jealousy, or that it measures a conscious, rational response rather than an evolved "gut" reaction. One study designed to test this possibility imposed a cognitive load on participants by asking them to remember a string of numbers while they considered the two infidelity scenarios (DeSteno et al., 2002). Since evolved mechanisms are supposed to be unconscious and automatic, if the evolutionary theory ofjealousy is correct then undermining a person's conscious processing ability with a cognitive load should increase or at least have no effect on the sex difference in jealousy responses. In actuality, although the cognitive load manipulation had no effect on men's ratings of which type of infidelity upset them more, it caused women to be more likely to list sexual infidelity as more upsetting (65% of those under cognitive load vs. 36% of those in control condition; DeSteno et al., 2002). These results call the forced-choice method of measuring jealousy, as well as the evolutionary hypothesis itself, sharply into question. In order to redeem and strengthen the evolutionary hypothesis, confirmatory data is needed from other methods of measurement. If Buss's findings are limited to the forced-choice methodology, and are observed only under conditions of minimal cognitive load, then they may reflect some "methodological artifact resulting from a specific and effortful decision strategy invoked by the format of the question," rather than an evolved tendency (DeSteno et al., 2002). Results from Continuous Measures. One potential alternative to the forced-choice measure is asking participants to rate their emotional reactions to the infidelity scenarios on a continuous, Likert-type scale. A number of studies have attempted to use this methodology, but thus far these attempts have yielded mixed results. Most researchers have found that when they ask participants to rate their level of upset or distress from Buss's scenarios on a continuous scale, there is no significant interaction between gender and infidelity type, and hence no sex difference in jealousy reactions to the two types of infidelity (Wiederman & Allgeier, 1993; DeSteno & Salovey, 1996; DeStens et aP., 2002; Sabini & Green, 2004). In response to these findings, Buss argues that continuous measures are not reflective of evolutionary sex differences because sf the "ceiling effect."This means that men and women respond to both infidelity scenarios at a very high level ofjealousy (i.e., they rate themselves as "extremely upset" for both), because it is evolutionarily advantageous for men and women to have a jealous reaction to both types of infidelity since they both signal threats to one's relationship and they tend to overlap so much in real life (Buss et al, 1999). Thus, because ratings of both types of infidelity cluster near the upper range of the response scale, it is difficult if not impossible to determine which of the two is relatively worse for men vs. women unless participants are forced to choose between them. A few recent studies have gathered data from continuous measures that appear to support the evolutionary hypothesis, but these studies can be called into question on methodological grounds. For instance, one study found a significant sex difference in the predicted direction on a continuous measure, but the continuous ratings were taken after the forced-choice question was asked, so subjects' responses could easily have been influenced by what they had previously seen (Sagarin, Becker, Guadagno, Nicastle, & Millevoi, 2003). Another study found a significant interaction between gender and infidelity type, but the phrasing of the question was different -instead of rating how "upset or distressed"they would feel, participants were asked to indicate how "jealous" they would be, which is a different question than Buss originally asked (Becker, Sagarin, Guadagno, Millavoi, & Nicastle, 2004). These findings are too inconsistent to conclude that the evolutionary hypothesis is supported by data from continuous measures of jealousy. This method of measurement does hold promise, but nothing conclusive can be demonstrated until the problem of the "ceiling effect"is dealt with. Results from Physiological Measures. One type of reaction that is not subject to self-presentation bias or altered by rational beliefs is the human body's unconscious physiological response to certain stimuli. Many jealousy studies, including the original one by Buss and his colleagues in 1992, have measured participants' physiological responses to imagined infidelity situations, in an attempt to determine whether the jealousy manifests itself physically in the sex-differentiated manner hypothesized by evolutionary psychologists. Unfortunately, a brief review of these studies will show that data from physiological measures of jealousy are even more mixed and inconclusive than those from continuous measure studies, and it is questionable whether this method is even an accurate measure of jealousy at all. Buss and his colleagues chose to measure participants' electroderrnal activity (EDA), pulse rate (PR), and electromyographic activity (EMG) as methods of assessing their physiological arousal in response to situations of imagined infidelity (1992). They found that men showed greater EDA for sexual infidelity than for emotional, women showed greater EDA for emotional infidelity than for sexual, men had a higher PR for sexual infidelity than emotional, women displayed no difference in PR for either infidelity scenario, and EMG data showed no significant effects for men or women (Buss et al., 1992). These data were interpreted as generally supportive of the evolutionary hypothesis, but Buss overlooked a number of problems. First of all, the EDA readings showed extreme variance, which sheds some suspicion on their value as a method of measurement (for example, the mean EDA reading for men imagining the sexual infidelity was 1.30 with a standard deviation of 3.64). Secondly, rather than comparing the measures between sexes, Buss considered them separately for each sex (e.g. men's EDA from sexual infidelity vs. men's EDA from emotional infidelity), which is inconsistent with the method he used to analyze the forced-choice responses (e.g. percentage of men who picked sexual as worse vs. percentage of women who picked sexual as worse). Lastly, and perhaps most importantly, there is no guarantee that these physiological measures have anything to do with jealousy -they are only assessing the body's level of arousal, which could be due to jealousy or perhaps to a different sort of sensation, such as the physical arousal one might experience when fantasizing about any sort of sexual, act, not specific to infidelity (Grice & Seely, 2000). More physiological studies followed the first one, attempting to address some of these limitations and increase power by testing more subjects. The results of these studies varied wildly, from supporting the evolutionary hypothesis on all measures (Piertzak et al., 2002), to finding no sex difference in arousal (Harris, 2000), to finding some results that were the exact opposite of what the evolutionary theory would predict (Grice & Seely, 2000). In one all-male sample, participants were aslted to imagine a baseline sexual scenario and a baseline emotional scenario as well as the sexual and emotional infidelity scenarios, and there was no difference between physiological response to the baseline sexual and the sexual infidelity -in other words, imagining a sexual situation was more arousing to men than imagining an emotional situation, regardless of whether that situation involved infidelity or not (Harris, 2000). A reasonable interpretation of these mixed results may thus be that this method of measurement is simply not useful for assessing sex differences in jealousy. Reactions to Actual vs. Hypothetical Infidelity. One common theme thoughout all of these different methods of measuring jealousy is that they all rely on the participants' ability to imagine a hypothetical situation of infidelity and react to it as if they were actually experiencing it. Clearly, this is not an optimal way of measuring someone's actual jealousy reaction because there is no way to know whether they would react in a similar fashion if the infidelity actually happened to them. Ethical concerns prohibit studies that would put participants in a situation where they honestly believe that their partner is cheating on them, so the only other possibility for examining people's responses to actual infidelity is to find a sample of participants who have been cheated on in the past, and ask them to indicate retrospectively which aspect of the infidelity bothered them more. A review of self-report studies with participants who had been victims of infidelity in the past shows that overall there is no evidence for a sex difference in which aspect of the infidelity causes the most distress (Harris, 2003). Males and females, including homosexual as well as heterosexual participants, both tend to focus on the emotional aspects of their partner's unfaithfulness when recollecting it. However, it can be argued that this method of assessing jealousy is even more dubious than asking for reactions to hypothetical infidelity. The correlational nature of these data (i.e., participants are not assigned to conditions randomly and there is every possibility that certain types of people are the victims of infidelity more than others) renders causal conclusions impossible. Moreover, retrospective reports such as these are notoriously unreliable and subject to any number of biasing influences. Finally, predictions derived from evolutionary theory are most relevant to individuals' tendency to become jealous over potential threats to their relationship, not to their emotional responses after the infidelity situation has already come and gone. This being the case, until someone can design a study that examines immediate reactions to actual infidelity without arousing ethical concerns, hypothetical situations of infidelity are the best method available for assessing jealous responses. Potential Moderating Factors As we have seen, there are many factors other than gender that can have a significant effect on a person's feelings ofjealousy. It is important not to disregard these factors when considering the data that have been collected on the subject thus far. If the sex difference found by Buss is not universal, that is, if one of these factors is strong enough to erase it entirely, then this throws the validity of the evolutionary hypothesis into question. An evolved tendency should be present in all samples, regardless of other influences such as age or culture. Age/Marital Status as a Moderating Factor. The majority of evolutionary jealousy studies have been performed with American undergraduate students as subjects. The sex difference in response to forced-choice questions is robust within this population, but as the age of participants increases, the data tend to become somewhat less reliable. Considerably fewer studies have been done with older participants, so it is difficult at this point to ascertain whether age is a significant moderator of jealousy. A meta-analysis of the few studies that have included participants older than 25 years shows that age does indeed have a significant effect on which type of infidelity people indicate is worse -the sex difference is stronger for college students than for older participants (Harris, 2003). Importantly, though, the sex difference is still significant for these older samples. One notable factor associated with age is the marital status of the participants. Only one study has been done to examine the effect of marital status on forced-choice jealousy responses, and this has provided some intriguing results (Voracek, 2001). A community sample of Austrian adults, with an average age of 32 and an age range of 18-58, was provided with Buss's original forced-choice infidelity items ("passionate sex" vs. "deep emotional attachment") and asked to choose which would upset or distress them more. Of those who were unmarried but in a committed relationship, 58.5% of men and 28.3% of women indicated that the sexual infidelity would be worse, a significant difference. The married sample, on the other hand, displayed almost no sex difference at all: 27.1% of men and 27.7% of women indicated that sexual infidelity would be worse. This striking result raises some interesting questions. Can marriage eliminate the robust sex difference that has been found across countless samples? If so, does this cast doubt on the notion that the sex difference is an evolved tendency? Clearly, further study of married samples is warranted, but even if this result were to be replicated and marriage were found to eliminate the sex difference in jealousy, caution should be taken before completely ruling out the evolutionary hypothesis. Marriage is a social contract that binds two people together for life and is very difficult to break. Consequently, married individuals have a much greater assurance that their relationship will be safe against rivals. This assurance is purely a result of the contract and all of the societal regulations that accompany it -the institution of marriage would not have existed early on in human evolutionary history, so our ancestors would not have had this type of guarantee. It could be that, once an individual is secure in the knowledge that it would be very difficult for a rival to threaten his or her relationship, evolved gut reactions of jealousy are subsumed by this assurance and replaced by more rational or cognitively-influenced answers. Unmarried couples are therefore likely to be a better source for testing evolutionary theories, because their relationships are not protected by the cultural shield of wedding vows. However, further study of married samples could still provide valuable insight into whether there truly are evolved sex differences in jealousy. Cultural Differences as a Moderating Factor. One of the key results needed to support a theory of evolved psychological differences is that the findings must replicate in cross-cultural studies. For the most part, the evolutionary theory of jealousy has performed well on this test. The forced-choice methodology has been employed with undergraduate samples in the U.S., Germany, the Netherlands, Sweden, Japan, and Korea, and every single experiment has found a significant sex difference overall in which type of infidelity is more upsetting (Buunk et al., 1996; Wiederrnan & Kendall, 1999; Buss et al., 1999). A meta-analysis of the data from these studies grouped by region (US, Asia, and Europe) found that this variable was not a significant moderator of gender differences in jealousy (Harris, 2003). Culture certainly does influence participants' overall pattern of responses -for instance, a higher percentage of American men than Japanese men chose sexual infidelity as the most upsetting (76% vs. 38%), but this trend was the same for American and Japanese women as well, so across cultures, the sex difference remains robust (Buss et al., 1999). Sexual Orientation as a Moderating Factor. Homosexuality has always posed an interesting conundrum for evolutionary psychologists, because as of yet there is no convincing Darwinian explanation for why some people would find themselves attracted to members of their own gender with whom they could not reproduce (Muscarella, 11 999). Due to this fact, most evolutionary studies of sex differences tend to exclude data from homosexual individuals because they complicate the hypothesis. It is difficult to know what to conclude from these data, but there have been a few evolutionary studies of jealousy using homosexual samples, and it is important not to disregard or overlook this unique subset of the population. A meta-analysis of data from studies with homosexual and heterosexual samples reveals that, predictably, there is a stronger sex difference in jealousy for heterosexual participants than for gays or lesbians (Harris, 2003). One study found a main effect of sexual orientation such that lesbians and gays were more likely than straight men and women to choose emotional infidelity as worse, which is consistent with previous findings that sexual exclusivity in a relationship is in general more important to heterosexual men and women than homosexuals (Harris, 2002). Disregarding this main effect, however, there was still a sex difference such that more gay men than lesbians chose sexual infidelity as the worse of the two (though the data was not shown in any form other than a bar chart, so it was impossible to tell if this difference was statistically significant). Another study found the exact opposite result, that 51% of lesbians and 32% of gay men rated sexual infidelity as the most upsetting, but findings from this study were suspect for two reasons: the sample was recruited entirely from gay bars in several Dutch towns, so 37% of participants were under the influence of alcohol when they participated in the study, and there was no heterosexual control group with which to compare their data (Dijkstra et al., 2001). From the insufficient amount of data that has been accrued using homosexual samples, the most solid conclusion one can come to is that the evolutionary theory of jealousy overall lacks support among this population. This is not surprising, given the fact that homosexuality itself is a phenomenon that still defies evolutionary explanation. Thus, I must do as other evolutionary theorists have done and set this challenge aside for the moment, but this is certainly an area that would benefit greatly from further research in the future. Jealousy as a Speczfic vs. Broad Mechanism Evolutionary psychology is a notoriously controversial area of study (Gould, 1991 ; Eagly & Wood, 1999) and this controversy has been played out in the literature on jealousy. Many opponents of the evolutionary theory of jealousy argue against it based on a particular interpretation of what the theory maintains. Some critics have adopted a very specific, narrow, rather simplistic definition that can be referred to as "JSIM,"the "jealousy as a specific innate module"definition. According to JSIM, "because sexual jealousy arose as a solution to cuckoldry, and emotional jealousy arose as a solution to resource loss, each problem would have been unique to each sex,"thus leading to the formation of jealousy as a distinct module in the brain that is different for men and women (Harris, 2003). This model leaves very little room for conscious thought or variation in behavior; all humans are expected to respond to infidelity in a certain predetermined manner based on the evolved tendencies of their gender. Clearly, if this were what was meant by the "evolutionary theory ofjealousy,"then it would have already been disproven many times over by the fact that jealousy varies by culture, that men are frequently more distressed by emotional than sexual infidelity, that married subjects show less of a sex difference than unmarried subjects, etc. The goal of evolutionary psychology is not to distill human behavior into a catalog of instincts and mechanical responses bred into us by natural selection, but to examine how humans interact with thelr environment and determine what role, if any, evolution may have played in shaping those interactions (Wiederrnan & Allgeier, 1993). Thus, any theory of evolutionary psychology that fails to take into account individual differences and rational behavior is incomplete at best. It would be much easier if the data supported the neat, uncomplicated JSIM hypothesis that men are always more upset by sexual infidelity and women are always more upset by emotional infidelity, but human psychology is much too complex to be reduced to such simple rules and instincts. The fact that JSIM is not supported, however, does not change the possibility that evolution may have played a role in the shaping of our jealous reactions. Consider the mating scenario faced by our ancestors over the course of evolution. Clearly, these individuals were not governed by the simple rule, "men care about sex, women care about emotional involvement."Human young are born helpless and take many years to reach maturity. Any male's offspring would have had a better chance of survival if he was emotionally invested and thus committed to providing for them and their mother. Consequently, males who formed a strong emotional bond with their mate may have held an evolutionary advantage over those who impregnated many females but didn't stay to provide for them (Harris, 2003). This could very well be why, in many samples, a majority of men were more upset by emotional infidelity than sexual. But for men, the problem of paternity uncertainty still remains -no matter how emotionally invested a man is, it will do him no good if the offspring he is providing for do not carry his genes. Thus, while emotional attachment is important, the problem of sexual infidelity should still be relatively more salient to men than to women. Another possibility is that jealousy may have evolved as a negative response to any relationship threat in general, rather than distinguishing between sexual and emotional threats. One theory holds that this general jealousy mechanism is first displayed in infants when their relationship with their mother is threatened (Harris, 2004). Sibling rivalry is a universal phenomenon, and babies as young as six months old have been found to display negative facial expressions when watching their mothers interact with a lifelike baby doll (Hart, Field, del Valle, & Letourneau, 1998). As a person matures and becomes involved in romantic relationships, the jealousy resulting from these relationships is hypothesized to be an extension of the sensitivity to general relationship threats that is evident in infants. However, if this theory of evolved jealousy is correct, then there should be no significant difference in what type of threat is more distressing to men vs. women. Jealousy may have evolved as a general mechanism in response to any sort of relationship threat, but different hard-wired "triggers"could be incorporated into this mechanism that would make certain types of threat more salient to males than to females, or vice versa. For example, although both men and women might be distressed if their partner spent a lot of money on another person, thus indicating a general threat to the relationship, this cue would be more salient and thus relatively more upsetting to women because it implies the diversion of resources. Similarly, seeing one's partner share an intimate hug with a rival may spark a jealous reaction in anyone, but men might find themselves relatively more distressed than women, because physical contact is an indication of sexual interest and thus it would trigger males' jealousy mechanism more strongly. In this way, the sex-differentiated theory of evolved jealousy can be combined with the theory ofjealousy as a response to general relationship threats, or also social- cognitive theories of jealousy. Of course humans will respond in a rational manner that may differ from individual to individual based on their interpretation of the situation, their cultural background, and so on, but underneath this conscious response could lie an evolved mechanism that has made different types of cues more salient to one sex than to another. With this study, I intend to test this notion of evolved sex-differentiated "triggers" that make a certain type of infidelity relatively more salient to one gender than another by using a novel methodology which also addresses a number of the weaknesses in previous evolutionary studies. First and foremost, it is crucial to note that in the vast majority of past self-report studies on jealousy, no matter what method of measurement the researchers used, the hypothetical situations presented to the participants were some variation of Buss's original scenarios: "your partner enjoys passionate sexual intercourse" vs. "your partner forms a deep emotional attachment" with another person, or "your partner tries different sexual positions" vs. "your partner falls in love"with another person (Buss et al., 1992). In all of these scenarios, the essential point to notice is that participants are being asked for their reaction after the act of infidelity has already occurred. If the evolutionary hypothesis is based on the idea that jealousy evolved as a method of protecting one's relationship from certain types of threat that could potentially harm one's reproductive success, then one could argue that measuring a person's level of distress after the infidelity has occurred is not a reliable way of assessing evolved sex differences in jealousy. In this situation, the male would have already been cuckolded or the female would have already lost her mate's attention to someone else (Harris, 2003). I believe it is more logical to assess people's responses to potential infidelity cues; in other words, different acts of "flirting" or other relatively mild behaviors that indieate a partner's sexual or emotional interest in a rival. Therefore, that is precisely the approach that this investigation will take. Surprisingly, very few evolutionary studies of jealousy have examined gender differences in reactions to milder situations of infidelity or flirting. This is due for the most part to a widespread reliance on Buss's original infidelity scenarios, in efforts to replicate (or disprove) his findings. However, data from one very recent study of selective memory indicate that investigating people's responses to pre-infidelity cues may prove to be instrumental in testing the evolutionary theory of jealousy (Schutzwohl & Koch, 2004). Participants listened to a hypothetical story containing five ambiguous cues to sexual infidelity and five ambiguous cues to emotional infidelity (as identified by Shackelford & Buss, 1997). The stories were presented either in a personally nonthreatening condition (protagonists were referred to as a male and a female first name) or a personally threatening condition (protagonists were referred to as "you" and "your partner"). One week later, participants were given a surprise recall test to see how many of each type of cue they could remember unprompted. In the personally threatening condition, there was a significant gender difference -men on average remembered 44% of the sexual cues and 29% of the emotional cues, while women remembered 25% of the sexual cues and 36% of the emotional cues. In the nonthreatening condition, there was no significant gender difference in recall. This supports the evolutionary hypothesis, not only because men recalled more sexual cues and women recalled more emotional cues, but also because the gender difference was only found in the personally threatening condition, thus indicating that the salience of sexual cues is context-dependent, and cannot be explained by the idea that men are simply more interested in and attuned to sexual content than women (Schutzwohl & Koch, 2004). Study 1 In the present study, I will follow this promising lead and expand upon the usual treatment of jealousy by further testing people's reactions to different types of relationship threats and pre-infidelity cues rather than reactions to infidelity that has already occurred. Additionally, this study will utilize a methodology that addresses the problem of the "ceiling effect" that has been encountered by previous researchers when using continuous scales to measure jealousy (Buss et al., 1999). Instead of a choice between two situations of extreme infidelity, participants will be presented with a range of hypothetical scenarios in which their partner engages in a behavior that could be taken as a cue to future infidelity. Seven of the scenarios will be exclusively emotional in nature and seven exclusively sexual. Participants will be asked to consider each behavior, one by one, and rate how upset they would be on a scale of 0-10 if their romantic partner were to engage in the behavior. The scenarios are designed to vary in their "inten~ity,~~ such that some will be rated as very upsetting (e.g. one's partner having a one-night stand with someone) and some as mildly upsetting (e.g. one's partner laughing at someone else's jokes). This design is meant to draw the jealousy responses away from the "ceiling" of the continuous scale enough to examine whether there is a significant gender difference. It will also address the issue of rating reactions to infidelity cues rather than distress afier the infidelity has already happened, because the scenarios are merely relationship threats, as opposed to the extreme acts of infidelity. The problem of the "double-shot"hypothesis will be eliminated by a) pre-testing a number of possible scenarios in order to select scenarios which are solely sexual or emotional rather than a blend of the two, and b) making it clear to the participants that no sexual contact has occurred in the emotional scenarios and no emotional connection is implicit in the sexual scenarios. Some researchers have brought up the objection that jealousy is a complex emotion that might have nuances that are not captured by such a simple characterization as "upset/distressed" (DeSteno et al., 2002; Harris, 2003; Sabini & Green, 2004). They argue that jealousy is composed of "lower-level states," such as anger, hurt, and sadness, and recently participants have been found to indicate more anger in response to sexual infidelity (because they see sexual infidelity as their partner's conscious choice) and more sadness in response to emotional infidelity (because falling in love is something that cannot be controlled; Sabini & Green, 2004). Due to these concerns about the oversimplification of the concept ofjealousy, the current study also asks participants to rate their responses on a variety of dependent measures, such as how "angry," "hurt," "jealous," and "sad" they would feel for each scenario, and how much of a "threat to their relationship" they viewed each scenario to be. The primary evolutionary hypothesis (Hypothesis 1) that I will test on all of these dependent measures can be divided into two predictions: a) men will have relatively higher ratings than women in response to the sexual scenarios, and b) women will have relatively higher ratings than men in response to the emotional scenarios. While the main focus of the evolutionary theory is on this interaction effect, the use of continuous measures also makes it possible to test a secondary hypothesis that has not previously been addressed by other researchers. The new prediction is that, due to evolutionary pressures imposed by human biological limitations, females should in general be more jealous (i.e. more sensitive to infidelity cues) than males. The evolutionary reasoning behind this hypothesis is that while both men and women should be sensitive to both types of relationship threat because of their implications for future reproductive success, women should be more sensitive overall because the loss of a relationship in which they have invested a good amount of time and resources is more reproductively costly to them than to men. Biologically, a woman's "window"of fertility is much smaller than a man's -while a woman can only bear healthy children from puberty to around the age of 40, a man is able to successfully father a child much later in life. This female age limit of fertility was probably even more significant to our ancestors, whose life spans were much shorter than ours today. Also, according to a number of evolutionary psychological studies, men find women less attractive as they get older, whereas many women consider an older man more attractive because he has experience, has accumulated wealth, etc. (Kenrick & Keefe, 1992). Clearly, if a long-term relationship between a man and a woman were to end around middle age, the man's chances of finding another, younger mate and still successfully raising children would be much higher than the woman's chances of doing the same. Thus, because the loss of a relationship would be so much more evolutionarily costly for a woman than a man, women should have a higher baseline sensitivity to all potential relationship threats. Following this reasoning, Hypothesis 2 predicts a main effect of sex such that women will display greater jealousy reactions overall than men. Preliminary support for this prediction can be seen in the results of many previous studies that have found an overall tendency for women to give higher ratings of distress at hypothetical infidelity than men (Hansen, 1985; deWeerth & Kalma, 1993; Shackelford & Buss, 1997; DeSteno et al., 2002; Dantzker & Eisenman, 2003; Becker et al., 2004; Sagarin & Guadagno, 2004). The standard explanation that has been offered for this finding is that women simply have a tendency to rate their emotions more strongly than men, not that they actually feel those emotions more strongly. Unfortunately, this hypothesis is non-falsifiable -it is impossible to objectively assess whether women are really feeling these emotions more strongly than men are, or whether they feel the same amount of emotion but simply rate it differently. This study provides an alternate possibility, derived from clear and logical evolutionary reasoning, that perhaps women genuinely are more sensitive to infidelity cues in general because the occurrence of the infidelity would be more costly to them than it would to men. Hypothesis 2 about the main effect of sex may at first seem to contradict the original evolutionary hypothesis that men will be more jealous than women about sexual infidelity and women will be more jealous than men about emotional infidelity, but in actuality it does not. Hypothesis 2 does not predict that women will have a stronger jealousy response to sexual infidelity cues than men, just that their combined response to both types of infidelity will be greater than men's combined response to both types. Hypothesis 1 on the other hand is about the interaction effect -the idea that after any main effects of gender and infidelity type have been considered, there will be a significant interaction between the two such that a) men will be relatively more bothered by sexual infidelity than women and b) women will be relatively more bothered by emotional infidelity than men, thus suggesting the possibility of evolved jealousy "triggers"that respond to different types of cues in men and women. Method Pilot Study Because this study required the creation of a number of original hypothetical infidelity scenarios that had never been tested before, it was first necessary to determine whether the new scenarios were appropriate tools to test the evolutionary hypothesis. In order to do this, many potential scenarios were written and tested in a pilot study, to eliminate those that did not meet the requirements. Specifically, the goal of the pilot study was to create an initial pool of hypothetical infidelity scenarios, and then to select from this pool a subset of scenarios that would a) span a range of mild to severe infidelity and b) be regarded as representing either exclusively emotional infidelity or exclusively sexual infidelity rather than an indistinguishable combination of the two. This would enable study participants to consider and rate the two types separately, thus eliminating the problem of the double-shot hypothesis. Twenty-two hypothetical infidelity scenarios were originally composed, 10 intended to be sexual in nature, 9 intended to be emotional, and for purposes of comparison, three intended to incorporate aspects of both types of infidelity. The scenarios were described as happening to a series of fictitious couples, with gender- typical names like "Jane" and "Bob." All of these scenarios were included in a pilot study questionnaire, and respondents were asked to indicate whether they believed each scenario to constitute an example of a) physical unfaithfulness without emotional unfaithfulness, b) emotional unfaithfulness without physical unfaithfulness, or c) physical unfaithfulness and emotional unfaithfulness together. For a complete list of scenarios used in the pilot study, see Appendix. The pilot study was presented to 10 subjects, five male and five female, and data -From their responses were used to determine the final scenarios to be used in the actual study. The six scenarios that had been rated by the most people as exclusively physical (mean = 8.67 of the 10 judges), and the six that had been rated by the most people as exclusively emotional (mean = 8.50 of the 10 judges) were selected as the final scenarios to be used in the study. The remaining scenarios were deemed too ambiguous to be labeled as exclusively "sexual"or "emotional"infidelity, and hence they were eliminated based on these results. Participants Participants in the main experiment were 92 undergraduate students (54 female and 38 male) recruited from an introductory psychology course at Williams College with the incentive of extra credit. Ages ranged from 17 to 22, with an average age of 19.26. From this original pool of participants, data from seven (all females) were eliminated due to previous knowledge of the evolutionary theory of jealousy that could potentially bias their responses, leaving a total sample of 85 participants (47 female and 38 male). Only one participant described herself as bisexual, and all other participants described themselves as heterosexual, so no data were eliminated due to sexual orientation (nor could its effects be assessed). Procedure and Materials Participants arrived for each session and were seated in a room in mixed-sex groups with no more than seven males or females in any given session, with males sitting on one side of the room and females on the other. Participants were told that they would be aslted to fill out a survey rating their emotional reactions to a series of 14 hypothetical scenarios having to do with relationships on a number of scales. After this brief description of the study, participants were given standard consent forms and informed that if at any point they felt uncomfortable answering the questions, they could leave them blank or choose to withdraw from the study without penalty. The cover sheet of the survey asked for demographic information (age, sex, sexual orientation) and whether or not the participant was in a committed relationship or had ever been in a committed relationship. If they were in a committed relationship, participants were asked to imagine that the scenarios pertained to their girlfriend or boyfriend. If they were not in a relationship at the time, participants were asked to recall a past relationship and answer the questions as they would have while in that relationship. If they had never been in a committed relationship, participants were asked to respond to the questions as they believed they would if they were in a relationship. The experimenter emphasized that participants were to keep in mind that the sexual scenarios and the emotional scenarios were completely independent of each other (i.e. that there was no emotional connection implicit in the sexual scenarios and no sexual contact implicit in the emotional scenarios) and to rate their reactions accordingly. Males and females were presented with all the same scenarios, but they were modified to be gender-appropriate (i.e. "your girlfriend"and appropriate pronouns vs. "your boyfriend" and appropriate pronouns). For example, one of the emotional scenarios read like this: "Your girlfriend and a male classmate of hers both spent the past summer working at an internship in New York City. Since then, the two have continued to tell inside jokes about their work experience -jokes that they find hilarious but that no one else understands. You ask her to explain the jokes but she says that she can 't -that you just wouldn 't understand because you weren 't there." There were 14 hypothetical infidelity scenarios in total, seven sexual in nature and seven emotional in nature (see Appendix for a list of all scenarios). Twelve of these were the original scenarios chosen from the results of the pilot study designed to ensure that the sexual and emotional scenarios were sufficiently separated from each other, and rephrased so that instead of involving imaginary characters like "Jane" and "Bob," they instead involved "you" and "your girlfriendlboyfriend." The other two scenarios were Buss's standard scenarios, "Your girlfriendlboyfriend has passionate sex with another madwoman" and "Your girlfriendlboyfriend forrns a deep emotional attachment to another madwoman.'' The inclusion of these two scenarios served as a comparison to determine whether the new scenarios accomplished their goal of bringing jealousy responses down away from the "ceiling"enough so that a difference between men's and women's reactions could be observed. Each scenario was written on a separate notecard, with a code number at the top. The seven emotional scenarios were grouped together and the seven sexual scenarios were grouped together, keeping the two infidelity types separate from each other. In some sessions of the experiment, the emotional scenarios were presented first, and in other sessions the sexual scenarios were presented first. Each batch was shuffled into a random order before each session and then distributed amongst the participants, with a verbal reminder, once again, that the scenarios were exclusively sexual, involving no emotional connection, or exclusively emotional, involving no sexual contact. Of course, males received the male versions of the scenarios and females the female versions. For each notecard, participants were instructed to write the code of the notecard at the top of their survey sheet, and then to rate their reactions to the scenario on the provided scales. The scales asked participants how overall upset, angry, hurt, jealous, and sad they would feel, how much of a threat to their relationship they would view the scenario, how upset they thought their significant other would be in the same situation, and how mild or severe the infidelity was (see Appendix for a reproduction of the survey scales).' Scales ranged from 0 10, with 0 labeled "not at all,"5 labeled "moderate,"and 10 labeled "extremely."Once each participant had finished rating all of his or her reactions to a scenario, all participants passed their notecard on to the next person and received a new one, until they had read and rated every scenario. Because each participant within a given session began with a different scenario -essentially starting at a different place in the "rotation,"-the order in which the scenarios were viewed was fully counterbalanced within each session. Moreover, because the cards were shuffled between sessions, the order of the rotation was different each time. Effectively, then, the scenarios were presented in a fully counterbalanced order. Once they were finished rating all of the scenarios, participants were thanked for their time and subsequently debriefed over email as to the purpose of the study. Results At the first stage of analysis, the goal was merely to determine whether there was a sex difference in rated response for each of the scenarios. In order to examine this, multiple t-tests were conducted comparing men's vs. women's responses to each scenario for each of the separate dependent measures: "overall upset,""anger," "hurt," 6'jealousy," I Some of these measures were for exploratory purposes only, to test preliminary ideas for future research, and thus will not be discussed in this thesis. "sadness," and "relationship threat."The results of these t-tests for each dependent measure were then grouped by infidelity type (sexual vs. emotional) for clarity. For a complete record of all t-values for each scenario, see Table 1. For the dependent measure "overall upset," there was a significant (ps 5 .O5) difference between men and women for 4 of the 7 emotional scenarios and a marginally significant (p = .lo) difference on 1 of the 7 emotional scenarios, whereas there were no significant sex differences for any of the sexual scenarios. Women were more upset by 5 of the 7 emotional scenarios than men, whereas the sexes were similarly upset by all of the sexual scenarios (for which scenarios specifically, see Figure 1). For the "angry" dependent measure, the difference between men's and women's scores were statistically significant (p < .05) for 1 of the emotional scenarios, marginally significant (ps < .lo) for 2 of the emotional scenarios, significant (p < .05) for 1 of the sexual scenarios, and marginal (p < .lo) for 1 of the sexual scenarios. Women were angrier than men in response to 3 of the emotional scenarios and 2 of the sexual ones (Figure 2). For the "hurt" dependent measure, there was a significant (p < .05) difference between men's and women's scores for 4 of the emotional scenarios, a marginal (p < -06) difference for 1 of the emotional scenarios, a significant (p < .05) difference on 1 of the sexual scenarios, and a marginal (p < .08) on 1 of the sexual scenarios. Thus, women reported themselves to be more hurt than men for 5 of the emotional scenarios and 2 of the sexual ones (Figure 3). On the "jealousy" dependent measure, there was a significant (ps < .05) difference between the sexes for 4 of the emotional scenarios, a marginal Cp < "10) difference on 4 of the emotional scenarios, and a significant (p < .05) difference on 1 of the sexual scenarios. Women reported more jealousy than men on 5 of 7 emotional scenarios and 1 of 7 sexual scenarios (Figure 4). For the dependent measure "sadness,"there was a highly significant (ps < .01) sex difference for 5 of the emotional scenarios, a significant (p < .05) difference for 1 more of the emotional scenarios, a significant (p < .05) difference for 1 of the sexual scenarios and a marginal (p < .lo) difference for 1 of the sexual scenarios. Women were more saddened by 6 of 7 emotional scenarios and 2 of 7 sexual scenarios than men were (Figure 5). Finally, for the dependent measure measuring "relationship threat,"there was a significant (p < .05) sex difference for 1 of the emotional scenarios, and a marginal (ps 5 .lo) difference for 2 of the emotional scenarios, and no sex difference for any of the sexual scenarios. Women rated 3 of the emotional scenarios as more of a threat to their relationship than men did, but the sexes rated all of the sexual scenarios similarly (Figure 6). In summary, the results of these t-tests revealed that women generally rated themselves higher (as being more upset, angry, hurt, and so on) than did men for both the emotional scenarios and (albeit to a lesser degree) the sexual scenarios. Indeed, in no case did men rate themselves significantly or marginally significantly higher than women on any of the dependent measures for any of the 14 scenarios. In order to examine the sex differences for each type of infidelity as a whole, the scores for all 7 scenarios of each type were collapsed together for each of the dependent measures (average a for emotional scenarios = .82, average a for sexual scenarios = .80). The resulting indexes were each subjected to a 2 (sex: male vs. female) x 2 (infidelity type: emotional vs. sexual) mixed-model analysis of variance (ANOVA) with infidelity type as a repeated measure. The first dependent measure to be analyzed in this manner was "overall upset."This analysis revealed marginally significant main effects for both sex and infidelity type, Fs(1, 83) = 3.76 and 3.55, respectively; ps = .056 and .063, respectively. On average, women reported that they were more upset about both types of infidelity cues than did men, and both men and women participants tended to be more upset about sexual cues than emotional. These main effects were qualified, however, by a marginally significant interaction, F(1, 83) = 3.76, p = .056 (Figure 7). Further analyses revealed that women were significantly more upset than men over the emotional scenarios, t(83) = 2.62, p = .01, but not the sexual scenarios, t(83) < 1. Similar 2x2 ANOVAs were subsequently conducted for each of the five remaining dependent measures. For the measure of "angry," there was a marginal main effect of sex, F(1, 83) = 3.34,p < .08, and a highly significant main effect of infidelity type, F(1, 83) = 33.36,~ < .0001. Women tended to rate themselves as more angry about both types of infidelity cues than did men, and sexual infidelity cues made male and female participants more angry than did emotional infidelity cues (see Discussion for speculation as to the reason behind this result). There was no significant interaction between these main effects (Figure 8). For the measure of "hurt," there was a highly significant main effect of sex, F(1, 83) = 8.44, p < .01, but no main effect for infidelity type, F(1, 83) = 1.47. In other words, women rated themselves as significantly more hurt than men did for both types of infidelity cues, but neither infidelity type on its own caused more hurt than the other. There was a significant interaction between these two factors however, F(1, 83) = 4.8, p < .05 (Figure 9). A subsequent simple effects analysis showed that women were significantly more hurt than men by the emotional scenarios, t(83) = 3.80,~ < .001, but not the sexual scenarios, t(83) = 1.37. For the measure of "jealousy,"sex did not have a statistically significant main effect, F(1, 83) = 1.55, but the main effect for infidelity type was highly significant, F(1, 83) = 24.04,~ < .0001. Men and women tended to rate themselves at similar levels of jealousy overall, but the emotional scenarios elicited higher ratings of jealousy than did the sexual scenarios. This main effect of scenario type was qualified by an interaction between the factors, F(1, 83) = 7.62,~ < .01 (Figure 10). Further analysis demonstrated that for emotional cues, women were significantly more jealous than men, t(83) = 2.68, p < .01, but for sexual cues, there was no significant difference, t(83) < 1. On the "sadness"measure, there was a highly significant main effect of sex, F(l, 83) = 9.89,~ < .Ol, but no main effect of infidelity type, F(1, 83) = .117. Thus, women tended to rate themselves as much more sad than men did in response to any type of relationship threat, while the emotional and sexual scenarios were rated as similarly saddening for all participants. This interpretation is also qualified by a marginal interaction, F(1, 83) = 3.6,~ < .07 (Figure 11). T-tests showed that the extent to which women were sadder than men in response to emotional infidelity cues was highly significant, f(83) = 3.73, g < .001, whereas women were only marginally sadder than men in response to sexual infidelity cues, t(83) = 1.80, p < .08. Finally, for the dependent measure of "relationship threat,"there was not a significant main effect for sex, F(1, 83) = 2.1 1, but there was a main effect of infidelity type, F(1, $3) = 5.23, g < .05. Men and women tended to give similar ratings of threat to their relationships, but the sexual scenarios were rated as more threatening overall than the emotional ones. There was a significant interaction between these factors, F(1, 83) = 3.87,~ = .05 (Figure 12). An analysis of simple effects showed that women rated the emotional scenarios as a significantly higher threat to their relationship than men did, t(83) = 2.21,~ < .05, whereas for the sexual scenarios, women and men showed no significant difference, t(83) < 1. Although significance levels varied from measure to measure, the overall pattern of findings was remarkably consistent. In each case, women tended to have more extreme reactions than men and the difference between women's and men's scores for the emotional scenarios tended to be greater than the difference for sexual scenarios. This interaction was at least marginally significant for every dependent measure except "angry."Because the data from each measure followed such a similar pattern, the scores from all of the separate measures (including "angry") were collapsed together to create a combined index of dependent measures (a for emotional items = .95, a for sexual items = .92). This index was then subjected to the same 2x2 ANOVA that each measure had faced separately. This analysis revealed a significant main effect of sex, F(l, 83) = 5.55, p < .05, such that on the whole, women tended to give higher ratings than men on all of the dependent measures. There was no main effect for infidelity type, F(1, 83) < 1; in other words, across all scales, sexual scenarios and emotional scenarios tended to be rated similarly. As expected, however, these findings were qualified by a significant interaction between the two factors, F(1, 83) = 5.29,~ < "05 (Figure 13). Further analysis revealed that for emotional infidelity cues, women tended to give higher scores across all dependent measures than men, t(83) = 3.16, p < .0 1, whereas for sexual infidelity cues, there was not a significant sex difference, t(83) = 1.03. Table 2 provides a record of mean responses on all measures, including the combined index. Discussion Contrary to the prediction of Hypothesis l(a), men were not found to be significantly more upset, angry, hurt, jealous, sad, or threatened by cues of sexual infidelity than women were. When all of these separate dependent measures were collapsed together to create a combined index, men's and women's reactions to the sexual scenarios of infidelity were not significantly different from each other (in fact, there was a nonsignificant trend for women to actually have a stronger reaction to the sexual scenarios than men did). On the other hand, consistent with the prediction of Hypothesis l(b), women were significantly more upset, hurt, jealous, sad, threatened, and marginally angrier about cues to emotional infidelity than men were. Given these results, it is not surprising that women's scores on the combined index of dependent measures were also much higher in response to emotional infidelity cues than men's were. What does this pattern of findings mean for the evolutionary hypothesis? One of its predictions appears to lack any support whatsoever, while the other pans out exactly as expected for every single dependent measure. It seems that perhaps the "androcentric" view of sexual jealousy that has been presented in previous theories is not entirely accurate. When explaining their findings, Buss and other evolutionary psychologists tend to paint a picture that focuses on the jealousy-crazed male driven by the threat of being cuekoPded, but according to the findings of this study, women appear to be just as responsive to cues of sexual infidelity as men are -in fact, in some cases, they are marginally more so. This finding is incompatible with the evolutionary argument that women have less of a need to worry about their mate's sexual infidelity since they can be certain that their offspring carry their genes. Only when considering cues to emotional infidelity does the prediction of the standard evolutionary hypothesis still apply, in that women appear to be more responsive to these cues than men are. One might at first take these data to mean that the evolutionary hypothesis is not supported. At best, its prediction came true for only one gender. However, before we can dismiss the evolutionary argument completely, we must consider the implications of the interaction effects that were found between gender and infidelity type. There was a significant or marginally significant interaction between these two factors on every single dependent measure except "angry."2 The interaction was also significant when all dependent measures were combined together. This can be interpreted in two different ways: that the difference between males' and females' reactions to sexual infidelity cues is different (in this case smaller) than the difference between their reactions to emotional infidelity cues, or that the difference between reactions to sexual vs. emotional infidelity cues is larger for men than it is for women. Regarding this second interpretation, it is important to note that we must be cautious when comparing reactions to the different types of infidelity within gender -after all, the scenarios that were chosen to represent sexual and emotional infidelity cues were unavoidably arbitrary, and there would be no possible way to make sure that the "intensity"of the sexual items objectively matched the "intensity"of the emotional items. In other words, if one were simply to compare women's responses to sexual vs. 2 This result can be understood when we consider the findings of Sabini & Green (2004), who showed that sexual infidelity reliably invoked more anger than emotional infidelity, an effect which displayed no gender differences. This was because all participants blamed their partner more for sexual infidelity, which they regarded as a choice, than emotional infidelity, which they regarded as uncontrollable. emotional cues, one couldn't necessarily conclude that women reacted to one more strongly than the other, because it could just be that the specific selection of cues that was chosen for that type of infidelity was objectively "worse"than the selection of cues for the other. However, it is meaningful to consider the interaction effect in this way, because both sexes are being included -if there is a significant sex difference in participants' relative reactions to emotional vs. sexual infidelity cues, then it cannot be due to the fact that one set of cues was simply "worse"than the other, because if that were the case then men's and women's pattern of responses to them would be the same. The fact that these interaction effects exist, and that they are in the direction that evolutionary theory would predict, leaves us with somewhat of an unclear picture. On the one hand, the finding that women consistently display as much of a jealousy response to sexual infidelity cues as men do goes against the evolutionary prediction, but on the other hand the finding that women are reliably more responsive than men to emotional infidelity cues, and the fact that there is a consistent gender difference in relative reactions to the two infidelity types (as evidenced by the interaction effects) argues that there may be some degree of truth to the evolutionary theory. As for Hypothesis 2 regarding the main effect of sex such that women would be overall more sensitive to infidelity cues than men, this prediction was borne out for the dependent measures "hurt," "sad," and the combined index of dependent measures (for which it was statistically significant), and also for "upset" and "angry"(for which it was marginally significant). On no dependent measure did men display stronger reactions than women. Although at this point it is still impossible to determine whether this finding is simply a result of women reporting higher baseline levels of emotionality than men (as theorized by DeSteno et al., 2002 and Sagarin & Guadagno, 2004) or if it is because they actually are more sensitive to infidelity cues, the results do support the hypothesis that women may have evolved to be more alert to any possible relationship threat. When interpreting the meaning of the main effect of sex, we must make it clear that this finding is qualified by the two-way interaction described previously. Though the results show that women are overall more responsive to infidelity cues than men, this is not because they are more jealous than men about sexual and emotional cues. Rather, their reactions to the sexual scenarios were consistently similar to men's, meaning that the main effect of sex was driven by the gender difference in responses to the emotional scenarios. Hypothesis 2 was supported because women's combined response to both types of cues was significantly stronger than men's combined response. One limitation of this and other similar studies that has been noted by a number of researchers in the past is that most of the results supporting the evolutionary hypothesis have come from samples of university students. Some studies using older, more diverse samples have demonstrated less robust results, and one study employing the forced- choice methodology with married participants provided findings inconsistent with the evolutionary theory (Voracek, 2001; Harris, 2003). The variability of these results in itself is an argument against the evolutionary hypothesis of jealousy -after all, if a sex difference in behavior is evolved, it should be evident to a certain degree in all human samples across age groups and across cultures. Otherwise it is liltely to be due to a more socially influenced or variable factor, such as the beliefs that one has been raised with or a cognitive state that changes with aging or marriage. Recall, however, that none of the existing studies have used items like those created in the present investigation. It is therefore conceivable that failures to support the evolutionary hypothesis with older samples have occurred not because the hypothesis is incorrect but because of ceiling effects or other methodological limitations. To address this concern, Study 2 was performed with an older, married sample of participants. Study 2 This phase of the experiment was an attempt to replicate the basic experimental design of Study 1 and test the same hypotheses with a sample of older, married individuals rather than college students. The intent of this approach was to aid in determining whether the results of Study 1 were due to an evolved mechanism or could perhaps be attributed to a more socially-influenced factor. Due to resource limitations and time constraints, the questionnaire for Study 2 was shortened and the sample size was smaller than that of Study 1. However, the new version of the questionnaire still followed the same experimental paradigm, and hence data from this study can provide some insight into the differences (or lack thereof) between the two populations. If the pattern of jealousy responses from married subjects were to be different than that of college students then it would be difficult to support the notion of an evolved jealousy mechanism. On the other hand, if Hypotheses 1 and 2 are similarly supported in Study 2 as in Study 1 despite the differing age and marital status of participants, this would provide evidence consistent with the argument that jealousy is an innate psychological adaptation selected for across human evolution. Method Participants A total of 33 heterosexual, married participants were recruited for Study 2, 16 males and 17 females. All participants lived in the Washington, DC metropolitan area. Average age of participants was 50.5 years, with a range of 25 years old to 79 years old. The average length of current marriage for all participants was 22.64 years, ranging in length from 1.5 years to 57 years of marriage to the same partner. Most participants had only been married once, but seven had been married once previously, and one had been married twice before. Procedure and Materials Participants were approached either in their workplace by a coworker or at a chorus rehearsal by a fellow singer. A basic explanation of the study was given that was similar to the explanation in Study 1, and consent forms were distributed in order to ensure that all participants knew that they could withdraw from the study at any time. If the participant agreed to take part in the research, he or she was provided with a shortened version of the original survey along with a blank envelope to seal the survey in once it was completed, to protect anonymity. Because no resources were available to provide subjects with incentive to participate, the surveys were greatly shortened in order to reduce the time commitment and inconvenience for the participants. Only four infidelity scenarios were chosen to be rated, two sexual and two emotional, chosen from the middle of the scale and slightly modified to be more appropriate for a married sample rather than college students (e.g. "Your husband informs you that he has decided to pursue an interest in theatre by auditioning for a part in a local play. At the casting call, the director mentions that one of the roles will involve a substantial amount of onstage kissing and some sexual contact with an actress who has yet to be cast. Your husband immediately volunteers for that role."; see Appendix for a full list of these modified scenarios). Each scenario was printed at the top of a page, with the same rating scales below it, and the order of the pages was shuffled randomly and then stapled into a simple packet that the participant could fill out and return in about 10 minutes. Participants were all provided with the contact information of the experimenter if they had any further questions or wished to learn the results of the study. None of the 33 participants requested this information. Results As in Study 1, the initial analyses consisted of a series of t-tests comparing the difference between men's and women's scores for each of the scenarios and each of the dependent measures individually. See Table 3 for a record of t-values for each scenario. On all 6 of the dependent measures, there was not a statistically significant or even marginally significant difference between men's and women's ratings for either of the sexual scenarios, allps > .lo. In other words, men and women rated themselves as comparably upset, angry, sad, jealous, hurt, and threatened in response to both of the sexual scenarios they were asked to consider. In keeping with the pattern of results from Study 1, analysis of the emotional scenarios revealed a different result. For one of the emotional infidelity scenarios (the one in which the spouse shares an inside joke with a rival), there was a significant (p < .05) difference between men and women's scores on the measures of "jealousy,""sadness,"and "relationship threat,"and a marginally significant (p < .lo) difference for "overall upset" and "hurt." Women rated themselves as more upset, hurt, jealous, sad, and threatened than men at the prospect of their spouse sharing an inside joke with a rival. The other emotional scenario (in which the spouse buys an expensive birthday present for a rival) showed a statistically significant difference between the sexes on the "jealousy" measure, p < .05, but not any of the other dependent measures (though several came close to marginal significance, withps just above .lo). Women rate themselves as significantly more jealous than men at the prospect of their spouse buying an expensive birthday present for another woman. After testing for gender differences on each individual scenario, scores for the 2 sexual scenarios and the 2 emotional scenarios were then collapsed together in order to compute a 2 (sex: male vs. female) x 2 (infidelity type: emotional vs. sexual) mixed-model ANOVA for each of the dependent measures (average a for emotional scenarios = .82, average a for sexual scenarios = .65). When the scale of "overall upset"was analyzed in this way, it revealed no main effect for sex, but a highly significant main effect of infidelity type, F(l, 3 1) = 9.01, p < .01. The emotional scenarios tended to make both men and women more upset than the sexual scenarios. This effect was qualified by a marginally significant interaction, F(1, 3 1) = 3.39, p < .08 (Figure 14). A simple effects analysis revealed that men's and women's ratings of "overall upset" were almost exactly the same for the sexual infidelity cues, t(3 1) = 0.1, whereas women rated themselves as more upset than men by the emotional infidelity cues (though this difference was not statistically significant, t(3 1) = 1.42, p = .17). A 2x2 ANOVA of the "angry"measure revealed no main effect for sex, but there was a main effect for infidelity type, F(1, 3 1) = 9.58, p < .Ol. In an interesting contrast to Study 1, the emotional scenarios tended to cause more anger in married participants than the sexual scenarios. There was no significant interaction effect for this measure (Figure 15). For the "hurt" measure, there was no main effect of sex, but again a highly significant main effect for infidelity type, F(l, 3 1) = 17.08, p < .001. Again, the emotional scenarios caused a greater amount of hurt to married participants than the sexual scenarios. The interaction between sex and infidelity type did not reach significance, F(l, 3 1) = 2.39, p = -13 (Figure 16). For the measure of "jealousy,"the analysis revealed a marginally significant main effect of sex, F(l, 3 1) = 3.47, p < .08, and a highly significant main effect of infidelity type, F(l, 3 1) = 14.87, p < .001. Married women displayed higher jealousy ratings overall than married men, and the emotional scenarios elicited greater jealousy overall than did the sexual scenarios. These main effects were qualified by a significant interaction, however, F(l, 3 1) = 5.56, p < .05 (Figure 17). Simple effects analysis revealed that women were significantly more jealous than men about emotional scenarios, t(31) = 2.52,~ < .05, but the gender difference in jealousy for the sexual scenarios was not significant, t(3 1) < 1. On the "sadness" measure, there was a marginally significant main effect of sex, F(1, 3 1) = 3.92, p < .06, and a highly significant main effect of infidelity type, F(l, 3 1) = 26.67, p < .000 1. Married women responded with more sadness overall than married men, and the emotional scenarios caused greater sadness overall than the sexual scenarios. There was also a significant interaction effect for this measure, F(1, 3 1) = 7.82, p < -05 (Figure B 8). Further t-tests showed that while women were significantly sadder than men about cues to emotional infidelity, t(30) = 2.46, p < .05, the gender difference in sadness about sexual infidelity cues was not statistically significant, t(30) = 1.08, p = .29. For the measure of "relationship threat," sex did not have a main effect on the data, but infidelity type did have a main effect, F(1, 31) = 6.29,~ < .05. Married subjects tended to rate emotional infidelity cues as more of a threat to their relationship than sexual infidelity cues. However, this finding was also qualified by a significant interaction effect, F(1, 31) = 5.79, p < .05 (Figure 19). Subsequent analysis of simple effects showed that married women rated the emotional scenarios as significantly more threatening than did married men, t(31) = 2.28, p < .05, but this gender difference was not significant for the threat of sexual infidelity, t(3 1) < 1. As in Study 1, the preceding analyses revealed a pattern that was consistent across virtually all of the dependent measures. Once again, women's and men's responses tended to differ more for emotional infidelity than they did for sexual infidelity. In addition, every single dependent measure in Study 2 showed a significant main effect for infidelity type such that the emotional scenarios were rated higher than the sexual scenarios. Due to these consistent patterns found in the data, scores from all of the separate dependent measures were again collapsed together to create an overall index (a for emotional scenarios = .97, a for sexual scenarios = .94), which was then subjected to the same 2x2 ANOVA. This analysis revealed no significant main effect for sex, but a main effect for infidelity type that was highly significant, F(1,3 1) = 27.65, p < .001. Married participants indicated that they would have more extreme reactions %s emotional infidelity than sexual infidelity, across all dependent measures. As in. Study 1, this main effect was qualified by a significant interaction, F(1, 3 1) = 4.61, p < .05 (Figure 20). The responses to emotional infidelity cues for married women were marginally higher than those of married men, t(3 1) = 1.90, p < .07, whereas there was no significant difference between men's and women's scores in response to sexual infidelity cues, t(31) < 1. For a summary of the mean responses on this and all other dependent measures in Study 2, refer to Table 4. Discussion Study 2 provided findings highly consistent with those of Study 1, suggesting that the pattern of data observed in Study 1 may be generalized to a population of older adults who are married. Men and women again showed highly similar reactions to the sexual infidelity cues -indeed, there were no significant gender differences in reactions to the sexual scenarios on any of the individual dependent measures or the combined index. In contrast, women were significantly more b'jealous," "sad," and "threatened" by the emotional scenarios than men, and had a marginally greater score on the combined index of dependent measures. This is the same half-support of Hypothesis 1 that was obtained in Study 1. Once again, it appears that women and men have a similar jealousy response to sexual infidelity cues, whereas women tend to be significantly more responsive to emotional infidelity cues than are men. As for the interaction between gender and infidelity type, the older, married participants of Study 2 again displayed a similar pattern to the college students in Study 1. There was a significant or marginally significant interaction effect on the measures of "upset," "jeal~us,'~ "relationship threat," "sad," and the combined index. In other words, on all of these measures, the gender difference in reaction to emotional infidelity cues was greater than the gender difference in reaction to sexual infidelity cues, and the difference between reactions to sexual vs. emotional cues for women was greater than the difference between these reactions for men. Notably, this second interpretation of the interaction effect manifests itself somewhat differently than in Study 1, in which the difference between reactions to sexual and emotional scenarios was greater for men than it was for women. This slight discrepancy in findings could be due to the fact that the data revealed an unexpected result, in the form of a robust main effect for infidelity type. Contrary to participants in Study 1, all married participants -men and women alike -tended to rate the emotional scenarios as worse than the sexual scenarios. This main effect was highly significant on every single dependent measure, and for the combined index. How can this discrepancy between Studies 1 and 2 be interpreted? One possibility is that this result may simply be attributable to the specific set of scenarios that I chose to present. Recall that Study 1 included 14 scenarios total, seven sexual and seven emotional, which were meant to span a broad range of possible infidelity cues, but Study 2 included only two of the sexual scenarios and two of the emotional scenarios. It could be that the two emotional scenarios that were chosen were simply objectively "worse" than the two sexual scenarios. In order to test this possibility, I went back to the data from Study 1 and selected out only the responses to the four scenarios used in Study 2 on the combined index of measures. A simple 2x2 ANOVA similar to the one performed in Study 2 was performed on these data to determine whether the two emotional scenarios selected were rated as significantly worse by the college sample than the two sexual scenarios selected. This analysis revealed that there was no significant main effect for infidelity type, F(1, 83) = .14 (mean rating for emotional scenarios = 5.34, mean rating for sexual scenarios = 5.27). This finding suggests that the consistent main effect for infidelity type found in Study 2 was not an effect of the specific scenarios that were selected, but rather can be attributed to inherent differences between the college-aged and the older, married sample. From these data, it appears as though young, unmarried people tend to get similarly jealous about emotional vs. sexual infidelity cues, whereas older, married people are overall more upset by emotional than sexual cues. I will put forth two, admittedly speculative, possibilities that may explain this phenomenon. First, as was discussed previously, marriage is a binding social contract, relatively recent in the course of human evolution and designed to increase assurance that partners will stay together despite threats to their relationship. The rational influence of this assurance could affect the expression of an evolved, "gut-reaction" jealousy mechanism, such that married individuals may feel less threatened by signs of sexual interest than signs of emotional interest, because they believe that minor sexual straying in a marriage is less likely to cause divorce than the possibility that their partner is developing emotional feelings for someone else. This theory is supported by the finding that, in one study, strong ma~orities of both men and women believed that a situation of emotional infidelity was more likely to indicate that their partner was about to leave them than a situation of sexual infidelity (Sabini & Green, 2004). Because age and marriage were confounded in this sample, I must also consider the possibility that age is the variable that changes participants' response patterns. Perhaps sex becomes less important in a relationship as individuals age, and greater focus is placed on emotional connection. In the study described above, a similar pattern of results was found for college students vs. an older sample: Older participants were more upset overall by an instance of emotional vs. sexual infidelity, whereas for a college sample this was not the case (Sabini & Green, 2004). This thesis is unable to determine which of these explanations is more likely, or if it is perhaps some combination of both, but these are just two examples of how variable factors can affect the expression of an evolved mechanism. Regardless of whether they are accurate or not, however, the main effect of infidelity type found in Study 2 does not change the fact that there was a significant and consistent interaction effect found in both samples such that the difference between males and females' reactions to sexual infidelity cues is significantly smaller than the difference between their reactions to emotional infidelity cues. This finding supports the evolutionary hypothesis. In contrast to the findings of Study 1 and numerous other studies assessing reactions to infidelity on a continuous scale (e.g., Hansen, 1985; deWeerth & Kalma, 1993; Shackelford & Buss, 1997; DeSteno et al., 2002; Dantzker & Eisenman, 2003; Becker et al., 2004; Sagarin & Guadagno, 2004), Hypothesis 2 about the main effect of sex was not supported in this married sample. Women were found to display marginally higher ratings than men overall on the measures of "jealous" and "sad," but this was not true for any of the other dependent measures or for the combined index, despite nonsignificant trends in this direction. This is an interesting result, given that it contradicts the findings of Study 1 as well as many others. Perhaps by differentiating between the two proposed explanations of this phenomenon, we can come to a better understanding of why the result may have changed in this study. Previous researchers have hypothesized that the main effect of gender that is typically found in continuous-scale studies such as this one is due to the fact that across the board, women simply have a natural tendency to rate themselves higher on subjective emotionality scales than men do (DeSteno et al., 2002, Sagarin & Guadagno, 2004). Hypothesis 2 of this study proposes an alternate explanation based in evolutionary logic, which is that women are more sensitive overall to relationship threats than men because the loss of a relationship would be more reproductively costly to them. Of these two explanations, only the second one offers a reason for why married women would be less likely to show a heightened level of jealousy than unmarried women. Similar to the effect it may have on which infidelity type is considered worse, the relationship security provided by marriage may dampen the overall heightened sensitivity to relationship threats that unmarried women experience. Of course, because age and marital status are confounded in Study 2, it falls to future research to untangle the relative influence of these variables. Nevertheless, this theory provides a possible explanation for why a main effect for sex was found in Study 1 but not Study 2, whereas the original explanation that all women simply rate their emotions more strongly than a11 men does not account for this finding. There is of course another possibility that may explain why a significant main effect for sex was not found in Study 2, which simply has to do with sample size. Because the sample of participants in Study 2 was regrettably much smaller than that of Study 1, there was reduced power and thus less of an ability to find statistically significant effects. The fact that the data from Study 2 show a consistent trend for women to have a stronger overall reaction to the infidelity scenarios than men, even though this trend was only significant for two dependent measures, suggests that had the sample size been larger perhaps significance would have been reached and Hypothesis 2 would have been supported after all. If this is indeed the case, then there is still no way to determine whether the evolutionary explanation or the explanation that women rate their emotions more strongly best accounts for the main effect of sex on jealousy found in Study 1 and previous research. In an attempt to determine why the main effect for gender was statistically significant in Study 1 but not Study 2, I went back and calculated the effect sizes for the main effect of sex on the overall index of measures in Study 1 and the trend on the same measure in Study 2 showing that women tended to display higher ratings overall than men. I found that in Study 1, for the main effect of sex, q2 = .063, and for the same but nonsignificant effect in Study 2, q2 = .057.' These effect sizes are comparable, suggesting that for both the college and the married sample, the effect of sex on jealousy ratings was similar. This means that the failure to find a significant main effect of sex in Study 2 was likely due to the simple fact that the sample size was much smaller, resulting in reduced power and thus less ability to find that an effect of the same size was statistically significant. Had the effect size for Study 2 been significantly smaller than that of Study 1, the other possibility that marriage might have the effect of lowering women's overall levels of jealousy would have been more likely. General Discussion The college-aged sample of participants in Study 4. and the older, married sample in Study 2 produced remarkably similar patterns of results when asked to rate their responses to cues of sexual and emotional infidelity on a series of continuous scales. Men According to Cohen's Conventions for Effect Sizes, an q2 of .06 is the standard for a "medium" effect. and women in both samples responded similarly to sexual cues, whereas women in both samples showed a stronger jealousy response than men regarding emotional cues. This repeated finding is embodied in the significant interaction effect that was also replicated for most measures in Study 1 and Study 2, showing that for both married and unmarried participants, there is a robust gender difference in relative sensitivity to the two infidelity types. Because the results of this experimental design were consistent for both samples despite different ages, social situations, and even marital status of the participants, they lend support to an evolutionary explanation of the findings. This is not to say that other, more variable, societal factors would not affect a participant's response on an individual basis, but on the whole the data demonstrate support for the argument that humans as a species have evolved sexually dimorphic response patterns to different types of infidelity threat. However, my findings did diverge from Buss's (1992) hypothesis and the theories of other evolutionary psychologists in an important way. Instead of the simple concept "men are bothered by sexual infidelity and women are bothered by emotional infidelity," the data from this experimental paradigm provide for a more nuanced view of gender differences in response to infidelity. The present results demonstrate that sexual infidelity cues elicit a similar jealousy response in men and women, whereas women are much more responsive to indications of emotional infidelity than men. What could be the evolved mechanism behind these findings? We how from the consistent interaction effect that men and women have different patterns of responses to sexual and emotional infidelity cues. This may be attributable to evolved "triggers9' that are sensitive to different cues in males than in females. Unfortunately, we cannot definitively conclude the precise direction of these sensitivities fi-om our data because we cannot guarantee the objective "equality"of each set of scenarios that was presented to the participants. In other words, we can conclude that the evolved jealousy triggers are sexually dimorphic, but it is impossible to determine whether this is because women are equally responsive to sexual and emotional cues whereas men are more responsive to sexual cues than emotional (as suggested by Study I), whether men are equally responsive to sexual and emotional cues whereas women are more responsive to emotional cues than sexual (as suggested by Study 2), or whether both patterns are correct, characterizing different views of young and older individuals, respectively. This distinction cannot be made because the inherent problem of using arbitrary infidelity scenarios prevents us from determining whether people actually are more sensitive to one infidelity type vs. another, or if this is just a result of the specific scenarios that were chosen. Regardless of the direction of this effect, however, this experiment still provides evidence consistent with the view that humans have evolved a sexually dimorphic response mechanism to different types of infidelity cues. In addition to illustrating the existence of this mechanism, the findings fi-om Study 1 and Study 2 also support the utility of the distinction between sexual vs. emotional infidelity that has been drawn in this and many previous jealousy studies. Whatever theory one entertains about the reasons behind the sex difference, the fact that men and women consistently respond in a different manner to sexual vs. emotional infidelity scenarios makes it clear that there are important psychological differences between the two. Though both types of infidelity do tend to occur together in everyday life, it is valuable to separate them for the purpose of assessing gender differences in jealousy responses. Regarding Hypothesis 2, that women would be more sensitive overall to relationship threats than men, the results were not quite as consistent across samples. Study 1 found a robust main effect of gender in the college sample such that women were indeed more sensitive than men to infidelity cues, but Study 2, though showing a similar trend, did not find this effect to be significant for the married sample. By comparing the effect sizes on the overall index of measures for Study 1 and Study 2 and finding that they were highly similar, I concluded that the lack of a statistically significant main effect in Study 2 is likely due to the fact that the sample size was much smaller than Study 1 and thus had less power to detect statistically significant differences. If married women and men really had similar levels of overall jealousy whereas young, unmarried women were overall more jealous than young, unmarried men, I would have expected to find a much smaller effect size in Study 2 than in Study 1. Because it is still impossible to determine whether women's overall higher ratings were due to their tendency to report stronger emotions than men on subjective scales or whether they really weremore upset, it must be left to future research to determine whether the robust main effect of sex is due to evolved tendencies, as Hypothesis 2 suggests. However, it is important to note that the findings of this study are not inconsistent with the evolutionary explanation. This thesis did include various limitations, some of which were inherent in the experimental design and others that may be addressed with future research. The fact that participants were asked to rate hypothetical scenarios raises the ever-present objection that their responses might not be indicative of responses to actual instances of infidelity. People are notoriously poor at predicting their emotional reactions to future or hypothetical events (Gilbert, Pinel, Wilson, Blumberg & Wheatley, 1998). However, due to obvious ethical considerations, it is impossible to subject participants to controlled experiences of a partner's actual infidelity. It is possible to ask participants to rate their reactions to infidelity experiences that they have had in the past (see studies reviewed in Harris, 2003) but because these responses are retrospective, and participants cannot be randomly assigned a condition, it is impossible to be sure whether they are accurate either. Given the restricted range of possibilities, responses to hypothetical scenarios are a reasonable and defensible approach to the study of sex differences in jealousy. Another limitation inherent in the design of the study was the fact that the scenarios presented to the participants as examples of sexual and emotional infidelity cues were unavoidably arbitrary. A pilot study ensured that the sexual and emotional scenarios were sufficiently differentiated from each other, and the experimenter attempted to provide a broad range of mild to severe instances of infidelity, but there was no way to ensure that the two sets of scenarios were equivalent, thus making it impossible to determine whether participants were more upset by sexual vs. emotional cues. It is important to note, however, that this limitation also applies to Buss's original scenarios (1992). How can one be sure that forming a "deep emotional attachment"is the emotional equivalent of "passionate sexual intercourse"? Some of the results found in previous studies may be due simply to individual differences in interpretation of the scenarios -for instance, passionate sexual intercourse is a straightforward example of extreme infidelity, whereas forming a deep emotional attachment could be interpreted as making a good friend, which is arguably not a relationship threat at all. It is important to be aware that no two scenarios or sets of scenarios can ever be considered as separate but equal instances of the two types of infidelity. Addressing other limitations could be the subject of future research. For example, a similar experimental design could be employed with more diverse and larger samples, to further test the evolutionary explanation. Cross-cultural replication is a commonly utilized method of providing support for evolutionary hypotheses (Buss, 1989; Buunk et al., 1996). It would also be useful to replicate Study 1 with older married and older unmarried samples of a larger size, in order to determine with more certainty whether the different main effects for sex and infidelity type found in Study 1 and Study 2 were due to methodological limitations or an inherent difference between samples, and to separate the confounded variables of age and marriage. A similar paradigm could also be tested, utilizing different infidelity scenarios in order to ensure that the results of this experiment were not an artifact of the specific items that were chosen to represent sexual and emotional infidelity threats. As evidenced by the findings of Study 1 and Study 2, data from this new experimental paradigm support the hypothesis that humans have evolved a sexually dimorphic jealousy mechanism that varies in relative sensitivity to different types of infidelity cues. Results are also consistent with the hypothesis that women have a higher combined level of jealousy than men due to evolutionary pressures. Both of these evolutionary theories still leave room for rational influence, however. By no means does an evolutionary explanation for human behavior indicate that all humans are mindlessly "programmed"to behave in a certain predetermined manner. On the contrary, both studies in this experiment found a large degree of variation in responses between individuals and personalities. Hypothesis 2 allows for the possibility that factors like marriage, age, or both, could influence the expression of women's evolved jealousy response. It is also possible that such factors may cause older, married men and women to be overall more upset by emotional than sexual infidelity. Human beings are thinking creatures whose individual actions may be determined by their experiences and beliefs as well as gut reactions, emotions, or evolved response mechanisms. Evolutionary theory merely characterizes patterns of behavior into overall tendencies that are likely to have been selected for over the course of human evolution. References Becker, D.V., Sagarin, B.J., Guadagno, R.E., Millevoi, A., & Nicastle, L.D. (2004). When the sexes need not differ: Emotional responses to the sexual and emotional aspects of infidelity. Personal Relationships, 11, 529-538. Buss, D.M. (1989). Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures. Behavioral and Brain Sciences, 12, 1-49. Buss, D.M., Larsen, R.J., Westen, D., & Semmelroth, J. (1992). Sex differences in jealousy: Evolution, physiology, and psychology. Psychological Science, 3,25 1- 255. Buss, D.M., Larsen, R.J., & Westen, D. (1996). Sex differences in jealousy: Not gone, not forgotten, and not explained by alternative hypotheses. Psychological Science, 7, 373-375. Buss, D.M. & Shackelford, T.K. (1997). From vigilance to violence: Mate retention tactics in married couples. Journal of Personality and Social Psychology, 72, 346- 361. Buss, D.M., Shackelford, T.K., Kirkpatrick, L.A., Choe, J.C., Lim, H.K., Hasegawa, M, Hasegawa, T., & Bennett, K. (1999). Jealousy and the nature of beliefs about infidelity: Tests of competing hypotheses about sex differences in the United States, Korea, and Japan. Personal Relationships, 6, 125-150. Buss, D.M. (2003). The evolution of desure: Strategies of human mating. New York: Basic Books. Buunk, B.P., Angleitner, A., Oubaid, V., & Buss, D.M. (1996). Sex differences in jealousy in evolutionary and cultural perspective: Tests from the Netherlands, Germany, and the United States. Psychological Science, 7, 359-363. Cramer, R.E., Abraham, W.T., Johnson, L., & Manning-Ryan, B. (2001). Gender differences in subjective distress to emotional and sexual infidelity: Evolutionary or logical inference explanation? Current Psychology, 20, 327-336. Daly, M. & Wilson, M. (1988). Homicide. New York: Aldine De Gruyter. Dantzker, M.L. & Eisenman, R. (2003). Sexual attitudes among Hispanic college students: Differences between males and females. International Journal of Adolescence and Youth, 11, 79-89. DeSteno, D.A. & Salovey, P. (1996). Evolutionary origins of sex differences in jealousy? Questioning the "fitness" of the model. Psychological Science, 7, 367-372. DeSteno, D.A., & Salovey, P. (1996). Genes, jealousy, and the replication of misspecified models. Psychological Science, 7, 376-377. DeSteno, D.M., Bartlett, M.Y., Braverman, J., & Salovey, P. (2002). Sex differences in jealousy: Evolutionary mechanism or artifact of measurement? Journal of Personality and Social Psychology, 83, 1103-1 116. deweerth, C. & Kalma, A.P. (1993). Female aggression as a response to sexual jealousy: A sex role reversal? Aggressive Behavior, 19, 265-279. Dijltstra, P., Groothof, H.A.K., Poel, G.A., Laverman, T.T.G., Schrier, M., & Buunk, B.P. (2001). Sex differences in the events that elicit jealousy among homosexuaBs. Personal Relationships, 8, 4 1-54. Eagly, A.H. & Wood, W. (1999). The origins of sex differences in human behavior: Evolved dispositions versus social roles. American Psychologist, 54,408-423. Gould, S. J. (1 99 1). Exaptation: A crucial tool for evolutionary psychology. Journal of Social Issues, 47,43-65. Grice, J.W. & Seely, E. (2000). The evolution of sex differences in jealousy: Failure to replicate previous results. Journal of Research in Personality, 34, 348-356. Hansen, G.L. (1985). Perceived threats and marital jealousy. Social Psychology Quarterly, 48, 262-268. Harris, C.R. & Christenfeld, N. (1996). Gender, jealousy, and reason. Psychological Science, 7, 364-366. Harris, C. & Christenfeld, N. (1996). Jealousy and rational responses to infidelity across gender and culture. Psychological Science, 7, 378-379. Harris, C. (2000). Psychophysiological responses to imagined infidelity: The specific innate modular view of jealousy reconsidered. Journal of Personality and Social Psychology, 78, 1082-109 1. Harris, C. (2002). Sexual and romantic jealousy in heterosexual and homosexual adults. Psychological Science, 13, 7-12. Harris, C. (2003). A review of sex differences in sexual jealousy, including self-report data, psychophysiological responses, interpersonal violence, and morbid jealousy. Personality and Social Psychology Review, 7, 102-128. Harris, C. (2004). The evolution of jealousy. American Scientist, 92, 62-71. Hart, S.T., Field, T., del Valle, C. & Letourneau, M. (1998). Infants protest their mothers9 attending to an infant-size doll. Social Development, 7, 54-6 1. Gilbert, D.T., Pinel, E.C., Wilson, T.D., Blumberg, S.J. & Wheatley, T.P. (1998). Immune neglect: A source of durability bias in affective forecasting. Journal of Personality and Social Psychology, 75, 6 17-63 8. Kenrick, D.T. & Keefe, R.C. (1992). Age preferences in mates reflect sex differences in human reproductive strategies. Behavioral and Brain Sciences, 15, 75-133. Muscarella, F. (1999). The homoerotic behavior that never evolved. Journal of Homosexuality, 37, 1-18. Pietrzak, R.H., Laird, J.D., Stevens, D.A., & Thompson, N.S. (2002). Sex differences in human jealousy: A coordinated study of forced-choice, continuous rating-scale, and physiological responses on the same subjects. Evolution and Human Behavior, 23, 83-94. Sabini, J. & Green, M.C. (2004). Emotional responses to sexual and emotional infidelity: Constants and differences across genders, samples, and methods. Personality and Social Psychology Bulletin, 30, 1375-1388. Sagarin, B.J., Becker, D.V., Guadagno, R.E., Nicastle, L.D., & Millevoi, A. (2003). Sex differences (and similarities) in jealousy: The moderating influence of infidelity experience and sexual orientation of the infidelity. Evolution and Human Behavior, 24, 17-23. Sagarin, B. J. & Guadagno, R.E. (2004). Sex differences in the contexts of extreme jealousy. Personal Relationships, 11, 3 19-328. Schutzwohl, A. & Koch, S. (2004). Sex differences in jealousy: The recall of cues to sexual and emotional infidelity in personally more and less threatening context conditions. Evolution and Human Behavior, 25,249-257. Shackelford, T.K. & Buss, D.M. (1997). Cues to infidelity. Personality and Social Psychology Bulletin, 23, 1034-1052. Shackelford, T.K., Buss, D.M., & Bennett, K. (2002). Forgiveness or breakup: Sex differences in responses to a partner's infidelity. Cognition and Emotion, 16, 299- 307. Townsend, J.M. (1 995). Sex without emotional involvement: An evolutionary interpretation of sex differences. Archives of Sexual Behavior, 24, 173-206. Voracek, M. (2001). Marital status as a candidate moderator variable of male-female differences in sexual jealousy: The need for representative population samples. Psychological Reports, 88, 553-566. Wiederman, M.W. & Allgeier, E.R. (1993). Gender differences in sexual jealousy: Adaptationist or social learning explanation? Ethology and Sociobiology, 14, 1 15- 140. Wiederman, M.W. & Kendall, E. (1999). Evolution, sex, and jealousy: Investigation with a sample from Sweden. Evolution and Human Behavior, 20, 12 1 -128. Acknowledgements Many thanks are due to all those who have made this thesis possible and who have supported me throughout the process. I am grateful for the help of all the Williams students who participated in my study, and also all of the married participants who took the time to fill out my survey. My parents were both an invaluable source of help in recruiting subjects for Study 2. More importantly, they have been a constant, unwavering presence of support throughout my life and in every endeavor that I have chosen to undertake. I would never have accomplished half as much if it weren't for them. Thanks to my suitemates and friends, who have kept me sane and preserved my sense of humor throughout the entire process. I would also especially like to thank Amy Shelton, my source of solidarity, sympathy, and computer help, who is sitting across from me even now as I put the final touches on my thesis at 4:00 AM. Finally and most importantly, I wish to express my appreciation for the help and guidance of my advisor, Ken Savitsky. Thanks for patiently responding to all of my panicked emails, working with me on the intimidating data analyses, correcting my silly grammar mistakes, and helping me turn my original, unformed idea into a final product that I can be (and am) proud of. Appendices Appendix A: List of Scenarios Used in Pilot Study (Male Version) ......................73 Appendix B: List of Infidelity Scenarios Used in Study 1 (Female Version) ............ 77 Appendix 6: Survey Cover Page/Instructions and Rating Scales for Study 1 ............ 79 Appendix D: List of Infidelity Scenarios Used in Study 2 (Female Version) ............ 80 Appendix E: Survey Cover Page/Instmctions for Study 2 ................................... 81 Appendix A: List of Scenarios Used in Pilot Study (Male Version) 1) Bob is out on a leisurely walk in the park with his girlfriend Jane on a nice spring day. He is trying to have a conversation with her, but she keeps getting distracted. When Bob looks over to see what has caught her attention, he realizes that her gaze is focused on a muscular man lying out on a blanket in the middle of the lawn, sunbathing without his shirt on. Jane appears to be admiring his body. 2) A new guy has recently joined the choir that Fred's girlfriend Carol sings in. She has taken it upon herself to introduce him to everyone and spend time with him outside of choir, so that he will feel comfortable integrating into the group. One afternoon Fred is walking by the cafk where he and Carol went on their first date when he spots her sitting alone at a table with the choir guy. She is leaning in closely to speak with him, and her hand is casually resting on his thigh. 3) Steve and his girlfriend Michelle are out dancing at a new nightclub. Both of them have been drinking a bit. After Steve returns from a trip to the bathroom, he finds Michelle in a different part of the club from where he left her, dancing closely with a male stranger. The two are not talking, but their bodies are very close together. The dance has been going on for several minutes, and Michelle seems very absorbed in it, giving no sign of having seen Steve standing there. 4) Mike asks his girlfriend Wendy if she wants to go out for dinner on Friday night, but she tells him that she has made other plans. She is vague about what these other plans are, but he is curious so he asks her directly what she is going to do. Wendy tells Mike that she can't go to dinner with him because she has dinner plans on Friday with an old boyfriend that she hasn't seen in forever, to catch up and reminisce about old times. 5) Rita always has a busy schedule, and very rarely can find any free time to spend with her boyfriend John. She is not only busy with work, but she also spends a lot of time socializing with her friends. John tries to work his schedule around her so that they can have some time together, but it is always a huge hassle. One day John realizes that over the past week, Rita has spent more time hanging out with her best guy friend than with him. 6) One evening, Hannah receives a phone call from her mother informing her that her grandfather, who was very close and dear to her, has passed away. Her boyfriend Kyle attempts to comfort her, but she pushes him away, telling him that she just needs some time alone. Kyle respects her wishes and she gets in her car and leaves for the evening, The next day, Hannah comes back and confesses to Kyle that after she left that night, she drove to her ex-boyfriend's house, who had known her grandfather well, and had cried to him about it. Overcome by their emotional distress, they ended up kissing, although Hannah immediately felt guilty and refused to have sex with him, though she did spend the night at his house. 7) George is on vacation with his girlfriend Betty at the beach. One day, the hotel they are staying at hosts a "wet T-shirt contest"that Betty decides to enter without asking George about it. She gets up on stage and has water poured over her while a crowd of guys that neither of them knows cheer raucously and make comments to each other about her body. Betty appears to enjoy the attention very much. 8) Bill and his girlfriend Cheryl are hanging out with a large group of friends at a coffee shop. One guy in particular is dominating the conversation, telling a bunch of stories and cracking jokes for the amusement of the group. Bill personally doesn't find his jokes all that funny, but Cheryl is in hysterics, wiping tears from her eyes and doubling over with laughter. When she can catch a breath, she begs the jokester to tell another story. On the way home, all Cheryl can talk about is how hilarious this person is. 9) As Nancy informs her boyfriend David, one of her best male friends is sick with a cold. She goes over to his room to bring him the notes from class. She also stays to make him some soup and tea, watches a movie to keep him company, and helps him do some laundry because he shouldn't be exerting himself. Nancy continues to take care of this guy every day until he feels better. 10) Pat confesses to her boyfriend Ryan that she had a dsunken one-night stand with someone about a month ago while he was out of town. The person she had it with was the cousin of one of her friends, who was just visiting for the weekend from out of town. She had never met this person before that one night, regrets the decision to sleep with him, and will probably never see him again. 11) Jillian has a very close relationship with one of her male friends from high school. She tells him about everything that happens to her, including whenever she has any fights or relationship problems with her boyfriend Henry. She is also very affectionate with this friend, hugging him whenever he greets her, sitting on his lap, and play-fighting when they get into an argument. 12) Chris and his girlfriend Diane are on a camping trip together. After a long day of hiking, Chris is completely exhausted and just wants to rest in the tent for a little while. However, Diane still has some energy left and wants to go swimming in the hot springs nearby. After taking a short nap, Chris decides to go join her at the springs. When he arrives, he finds her in the water alone with another male hiker that she doesn't know, both in their underwear, which they have been using as bathing suits. 13) On her way out the door to go to a concert with her boyfriend Patrick, Mary realizes that she has forgotten the tickets. Patrick offers to run up to her room and get them. As he is searching for the tickets on her desk, he comes across a letter written in Mary's handwriting. After a quick glance, he realizes that it is a love letter she has written to someone she doesn't know. She has not physically cheated on Patrick with this person, but she is in love with him, and wants to know ifhe feels the same way. 14) While on a business trip without her boyfriend Mark, Alice visits a massage parlor, where she receives a "sensual massage"from an attractive male masseuse. Although the massage does not involve sexual intercourse, it does include full nudity and some genital stimulation. 15) Vicky obsesses all week about what she should get one of her male friends for his birthday. Eventually, she decides on something that she deems "special" enough, goes out and spends a lot of money on it. Her boyfriend Zach can't help but think back to his last birthday, which Vicky forgot and then bought a belated card and took him out to a movie to make up for it. 16) Robert is riding on the bus with his girlfriend Carrie. It is quite crowded, and both of them are standing up, holding onto the overhead bars. Robert is slightly separated from Carrie because there are so many people on the bus. At one of the stops, an attractive, muscular man that neither of them has ever seen before steps on and looks around for a good place to stand. As the man squeezes past Carrie, she raises her eyebrows and then exchanges an appreciative look with the girl standing next to her. 17) Andrew's girlfriend Sally has been planning a "night out with the girls" for the past month and is very excited about it. Andrew completely understands that she wants a little time alone with her friends, and he spends the evening at a movie with an old friend he hasn't seen in a while. When he gets back later that night, Andrew finds out that Sally's night out with her fi-iends was spent at a male strip club in town. 18) Emily asks her boyfriend Dan's honest opinion about a paper that she is writing. He reads it through and points out a few weak spots to her, suggesting some changes she could make to improve on it. The next day, Emily gives the same copy of her paper to a male friend and asks him what his opinion is. He reads the paper and tells her that it looks good to him, and he wouldn't change a word of it. Emily disregards Dan's suggestions and turns in the paper without making any revisions. 19) Ellen tells her boyfriend Greg that she has decided to pursue an interest in theatre by auditioning for a part in a local play. At the casting call, the director mentions that one of the roles will involve a substantial amount of onstage kissing and some sexual contact with an actor who has yet to be cast. Ellen immediately volunteers for that role. 20) Eve is riding in the elevator of a high rise office building without her boyfriend Brian when there is an earthquake and the building loses power. The only other person in the elevator is a young man whom she does not know. The elevator is stuck between two floors and she and the man are trapped for several hours. It is a harrowing experience and they become close as a result of the ordeal. 21) Ann and a male classmate of hers both spent the past summer working at an internship in New York City. Since then, the two have continued to tell inside jokes about their work experience -jokes that they find hilarious but that no one else understands. Ann's boyfriend Jeff asks her to explain the jokes but she says that she can't -that he just wouldn't understand because he wasn't there. 22) Sarah goes to Florida for spring break with a bunch of her girl friends and without her boyfriend Phil. While there, she participates in an MTV game show event in which she is partnered with a male college student that she does not laow. They compete in a number of events to win prizes such as the "suck-and-blow"card game, popping balloons between their bodies, and quickly switching bathing suits inside a dressing room. Appendix B: List of Infidelity Scenarios Used in Study 1 (Female Version) Emotional Scenarios - Your boyfriend always has a busy schedule, and very rarely can find any free time to spend with you. He is not only busy with work, but he also spends a lot of time socializing with his friends. You try to work your schedule around him so that the two of you can have some time together, but it is always a huge hassle. One day you realize that over the past week, though there has been no sexual contact involved, your boyfriend has spent more time hanging out with his best female friend than with you. - Your boyfriend and a female classmate of his both spent the past summer working at an internship in New York City. Since then, the two have continued to tell inside jokes about their work experience -jokes that they find hilarious but that no one else understands. You ask him to explain the jokes but he says that he can't -that you just wouldn't understand because you weren't there. - On your way out the door to go to a concert together, your boyfriend realizes that he has forgotten the tickets. You offer to run up to his room and get them. As you are searching for the tickets on his desk, you come across a letter written in his handwriting. After a quick glance, you realize that it is a love letter he has written to someone you don't know. He has never physically cheated on you with this person, but he is in love with her, and wants to know if she feels the same way. - Your boyfriend obsesses all week about what he should get one of his female friends for her birthday. Eventually, he decides on something that he deems "special" enough, goes out and spends a lot of money on it. You can't help but think back to your last birthday, which your boyfriend forgot and then bought a belated card and took you out to a movie to make up for it. - You and your boyfriend are hanging out with a large group of friends at a coffee shop. One girl in particular is dominating the conversation, telling a bunch of stories and cracking jokes for the amusement of the group. You personally don't find her jokes all that funny, but your boyfriend is in hysterics, wiping tears from his eyes and doubling over with laughter. When he can catch a breath, he begs the jokester to tell another story. On the way home, all your boyfriend can talk about is how hilarious this person is. - One of your boyfriend's best female friends is sick with a cold. He goes over to her room to bring her the notes from class. Without any sexual intentions toward this girl, your boyfriend also stays to make her some soup and tea, watches a movie to keep her company, and helps her do some laundry because she shouldn't be exerting herself. He continues to take care of this girl every day until she feels better. -Your boyfriend forms a deep emotional attachment to another woman. Sexual Scenarios - Your boyfriend has been planning a "night out with the guys"for the past month and is very excited about it. You completely understand that he wants a little time alone with his friends, and you spend the evening at a movie with an old friend you haven't seen in a while. When you get back later that night, you find out that your boyfriend's night out with his friends was spent at a female strip club in town. - Your boyfriend informs you that he has decided to pursue an interest in theatre by auditioning for a part in a local play. At the casting call, the director mentions that one of the roles will involve a substantial amount of onstage kissing and some sexual contact with an actress who has yet to be cast. Your boyfriend immediately volunteers for that role. - Your boyfi-iend confesses to you that he had a drunken one-night stand with someone about a month ago while you were out of town. The person he had it with was the cousin of one of his friends, who was just visiting for the weekend from out of town. He had never met this person before that one night, regrets the decision to sleep with her, and will probably never see her again. - Your boyfriend goes to Florida for spring break with a bunch of his guy friends. While there, he volunteers for and gets chosen to participate in an MTV game show event in which he is partnered with a female college student that he does not know. They compete in a number of events together such as the "suck-and-blow" card game, popping balloons between their bodies, and quickly switching bathing suits inside a dressing room. - You and your boyfriend are out dancing at a new nightclub in town. Both of you have been drinking a bit. After you return from a trip to the bathroom, you find your boyfriend in a different part of the club from where you left him, dancing closely with a female stranger. The two are not talking, but their bodies are very close together. The dance has been going on for several minutes, and your boyfriend seems very absorbed in it, giving no sign of having seen you standing there. - While on a business trip in another state, your boyfriend visits a massage parlor, where he receives a "sensual massage" from an attractive female masseuse. Although the massage does not involve sexual intercourse, it does include full nudity and some genital stimulation. - Your boyfriend has passionate sex with another woman. Appendix 6: Survey Cover Page/Instructions and Rating Scales for Study 1 Please be aware that all of your answers to the following questions will remain completely anonymous. Consent forms are separate from this survey, and serve only to comply with standard research policies. Please do your best to answer all questions honestly. However, if you do feel very uncomfortable about any particular item, you may choose not to answer that question. DEMOGRAPHICS: Age: Gender: Male Female Sexuality: Heterosexual Homosexual Bisexual Other Are you currently in a committed romantic relationship? If not, have you ever been in a committed relationship before? Yes No INSTRUCTIONS: You will be presented with 14 hypothetical scenarios, each on a notecard, and asked to rate what your reaction would be to each one on a number of scales. Please do your best to really imagine yourself in these scenarios and rate your true gut reaction. If you are currently in a relationship, imagine that your boyfriend or girlfriend does the following things. If you are not currently in a relationship, please recall a past meaningful relationship and answer these questions as you would have while in that former relationship. If you have never been in a relationship, please answer as you believe you would in a loving, committed romantic relationship. This survey contains two kinds of scenarios related to relationship behaviors: items that may or may not be considered sexual infidelity, and items that may or may not be considered emotional infidelity. Please keep in mind that although the two may tend to co-occur in real life, they are beingpresented here independently. The sexual scenarios are "roma~ice-free" and the emotional scenarios are "sexual contact-fiee." After you read each scenario, please take at least 10 seconds to picture it in your mind and consider what your reactions would be. Then rate your reactions on the provided scales (be sure to write the scenario number at the top of the page!). Some of the scales may seem to you to be asking for the same thing -if this is the case, feel free to rate them the same. Once everyone has finished rating their responses, the experimenter will provide you with the next scenario. Thadc you for your participation! Appendix D: List of Infidelity Scenarios Used in Study 2 (Female Version) Emotional Scenarios - Your husband and a female coworker of his both spent a week working together full-time at a conference in New York City. Since then, the two have maintained a close friendship and tell inside jokes about their work experience -jokes that they find hilarious but that no one else understands. You ask him to explain the jokes but he says that he can't -that you just wouldn't understand because you weren't there. - Your husband obsesses all week about what he should get one of his female friends for her birthday. Eventually, he decides on something that he deems "special" enough, goes out and spends a lot of money on it. You can't help but think back to your last birthday, which your husband forgot and then bought a belated card and took you out to a movie to make up for it. Sexual Scenarios - Your husband informs you that he has decided to pursue an interest in theatre by auditioning for a part in a local play. At the casting call, the director mentions that one of the roles will involve a substantial amount of onstage kissing and some sexual contact with an actress who has yet to be cast. Your husband immediately volunteers for that role. - You and your husband are spending the night out dancing at a holiday party hosted by the company you work for. Both of you have been drinking a bit. After you return from a trip to the bathroom, you find your husband in a different room from where you left him, dancing closely with a female stranger. The two are not talking, but their bodies are very close together. The dance has been going on for several minutes, and your husband seems very absorbed in it, giving no sign of having seen you standing there. Appendix E: Survey Cover PageIInstructions for Study 2 Please be aware that all of your answers to the following questions will remain completely anonymous. Consent forms are separate from this survey, and serve only to comply with standard research policies. Please do your best to answer all questions honestly. However, if you do feel very uncomfortable about any particular item, you may of course choose not to answer that question. DEMOGRAPHICS: Age: How long have you been married? Were you ever married before this? (How many times?) You will be presented with 4 hypothetical scenarios and asked to rate what your reaction would be to each one on a number of scales. Please do your best to really imagine yourself in these scenarios and rate your true gut reaction. This survey contains two different kinds of scenarios related to relationship behaviors: items that may or may not be considered sexual infidelity, and items that may or may not be considered emotional infidelity. Please keep in mind that although the two may tend to co-occur in real l$e, they are beirzgpresented here independently. The sexual scenarios are "romance-free"and the emotional scenarios are "sexual contact-free." After you read each scenario, please take at least 10 seconds to picture it in your mind and consider what your reactions would be. Then rate your reactions on the provided scales. Some of the scales may seem to you to be asking for the same thing -if this is the case, feel free to rate them the same. Once you have finished rating all 4 scenarios, place the questionnaire in the blank envelope and seal it to ensure anonymity. Please sign the consent form separately and do not include it in the envelope, as this would associate your name with your answers. If you wish to find out more about the study or its results once I have finished compiling and analyzing the data, feel free to email me at: OSrma@williams.edu. Thank you for your participation. Sex Differences in Jealousy 82 Table I. Results from t-tests comparing men's and women's responses to sexual and emotional infidelity, Study 1. Dependent Measure Scenario Overall Upset Angry Hut Jealous Sad Relationship Threat Emofional t df P t df P t df P t df P t df P t d f P Busy schedule 1.64 83 .lo5 1.69 83 .095 3.54 83 ,001 2.26 83 ,026 3.33 83 .001 1.65 83 .lo2 Inside joke 2.13 82 ,036 1.93 82 .057 4.28 82 .000 2.27 82 .026 2.88 82 .005 1.72 82 .090 Love letter 2.28 83 .025 0.60 83 .552 1.92 83 ,058 1.59 83 ,116 3.68 83 .OOO 2.48 83 .015 Birthday present 2.50 82 .014 2.41 82 .018 2.53 82 .013 1.69 82 .095 3.04 82 ,003 1.61 82 ,112 Laugh at jokes 0.69 83 ,492 0.70 83 .486 0.79 83 ,431 1.21 83 ,229 1.07 83 ,288 0.58 83 .561 Care for sick friend 1.36 83 .I76 0.95 83 ,346 1.45 83 .I49 2.12 83 ,037 2.08 83 "040 1.51 83 .I34 Deep emot attchmt 1.98 81 .051 0.67 83 ,501 2.69 83 .009 2.39 83 .019 3.06 83 .003 1.39 83 .I69 Sexzla 1 Passionate sex 1.45 83 .I50 0.74 83 .459 1.81 83 .073 0.19 83 ,847 1.60 83 .I12 0.36 83 .720 Night at strip club 1.58 82 .I17 1.82 82 .072 1.58 82 ,073 2.06 82 .043 1.68 82 ,096 1.39 82 .I68 Kissing part in play 0.12 83 ,916 0.37 83 .713 0.41 83 .680 0.76 83 ,451 0.47 83 .640 0.06 83 .949 One-night stand 0.23 81 .822 1.44 82 .I53 0.14 82 ,886 1.03 82 .305 0.99 82 .326 1.36 82 ,177 Dance wlstrangen: 1.13 81 .263 3.04 83 .003 2.60 83 ,011 0.75 83 .456 2.58 83 .012 0.77 83 ,440 Sensual massage 1.49 83 .I41 0.57 83 ,572 0.34 83 .735 1.55 83 .I25 0.64 83 ,526 0.62 83 ,534 Table 2. Mean scores for males vs. females on emotional and sexual infidelity cues, Study 1 Infidelity Type . .- Dependent Measure Emotional Male (SD) Female (SD) .. , Sexual Male (SD) Female (SD) .. r , , Overall Upset 5.70 (1.76) 6.55 (1.22) 6.32 (1.52) 6.54 (1.40) Hurt 5.20 (1.69) 6.42 (1.26) 5.77 (1.59) 6.26 (1.64) Jealous 6.06 (1.99) 7.07 (1.47) 5.62 (1.82) 5.48 (2.13) Sad 4.65 (1.84) 6.01 (1.51) 4.93 (1.70) 5.61 (1.74) Relationship Threat 4.63 (1.67) 5.33 (1.26) 5.28 (1.41) 5.38 (1.45) Combined Index 5.19 (1.59) 6.16 (1.24) 5.64 (1.45) 5.96 (1.39) Sex Differences in Jealousy 84 Table 3. Results from t-tests comparing men's and women's responses to sexual and emotional infidelity, Study 2. Scenario Emofional Birthday present Overall Upset t df p 0.80 31 .430 t 0.54 Angry df 31 P ,595 t 0.86 Dependent Measure Hurt Jealous df P t df p 30 ,397 2.49 29 ,019 t 1.62 Sad df 30 p ,117 Relationship Threat t df P 1.54 31 ,134 Inside joke 1.79 31 ,083 1.10 30 ,281 1.77 30 .087 2.58 31 ,015 2.81 29 .009 2.38 31 .024 Sexual Dance w/stranger 0.13 31 .901 0.20 31 343 0.41 30 ,682 1.59 30 .I22 1.44 29 .I61 0.29 31 ,777 Kissing part in play 0.30 3 1 ,766 0.25 30 205 0.39 30 .696 0.09 31 ,932 0.63 30 ,532 0.13 31 ,900 Table 4. Mean scores for males vs. females on emotional and sexual infidelity cues, Study 2. Infidelity Type Dependent Measure Emotional Male (SD) Female (SD) Sexual Male (SD) Female (SD) Overall Upset 5.59 (2.77) 7.06 (3.14) 5.16 (2.31) 5.23 (2.08) Hurt 5.41 (2.92) 6.97 (3.24) 4.44 (2.41) 4.84 (2.41) Jealous 4.28 (2.29) 6.71 (3.13) 3.75 (2.41) 4.50 (2.66) Sad 3.91 (2.94) 6.66 (3.37) 3.03 (2.08) 3.94 (2.62) Relationship Threat 3.34 (1.97) 5.03 (2.25) 3.31 (2.13) 3.50 (2.32) Combined Index 4.65 (2.28) 6.38 (2.90) 4.04 (1.91) 4.40 (2.26) Sex Differences in Jealousy 86 Emotional Scenarios 0 1 2 3 4 5 6 7 8.89 6.72 6.5 6.29 4.24 4.16 3.34 + Male +Female 9.6 7.77 7.54 6.98 5.3 4.51 4.19 Scenario 1 Secret love letter 5 Inside joke 2 Deep emotional attachment 6 Laughs at rival's joke 3 Expensive bday present 7 Takes care of sick friend 4 Busy schedule 9 =p < .05, A =p < .10 Sexual Scenarios 0 1 2 3 4 5 6 7 -Male 9.68 8.75 6.84 6.76 4.74 4.79 2.95 9.91 8.68 7.33 5.96 5.21 4.85 3.85 -Female Scenario 1 Passionate sex with another 5 Sexual MTV games 2 Drunk one-night stand 6 Audition for lcissing role in play 3 Dancing closely with stranger 7 Night out at strip club 4 Sensual massage =p<.05 A =p<.lO Figure 1. Male vs. female ratings by scenario for "overall upset,"Study 1. Sex Differences in Jealousy 87 Emotional Scenarios lo -.Female1 8.19 16.09 16.98 16.34 14.65 13.81 13.13 Scenario 1 Secret love letter 5 Inside joke 2 Deep emotional attachment 6 Laughs at rival's joke 3 Expensive bday present. 7 Takes care of sick friend 4 Busy schedule 4 =p< .05, A =p < .10 Sexual Scenarios 1 2 3 4 5 6 7 4.53 4.16 2.46 6.34 6.42 8.24 9.29 -c- Male 6.09 5.11 4.4 3.6 8.81 7.81 -Female 9.53 Scenario 1 Passionate sex with another 5 Sexual MTV games 2 Drunk one-night stand 6 Audition for lussing role in play 3 Dancing closely with stranger 7 Night out at strip club 4 Sensual massage 4 =p<.05 n=p<.10 Figure 2. Male vs. female ratings by scenario for "how angry,"Study 1. Sex Differences in Jealousy 88 Emotional Scenarios A 0 4 1 2 3 6 7 5 6.74 9 6.55 5.92 3.11 2.74 2.37 -c Male 7.85 7.57 3.17 9.57 8.04 5.52 3.26 + Female Scenario 1 Secret love letter 5 Inside joke 2 Deep emotional attachment 6 Laughs at rival's joke 3 Expensive bday present. 7 Takes care of sick friend 4 Busy schedule 4 =p < .05, a =p < .10 A Sexual Scenarios Scenario 1 Passionate sex with another 5 Sexual MTV games 2 Drunk one-night stand 6 Audition for kissing role in play 3 Dancing closely with stranger 7 Night out at strip club 4 Sensual massage 4 =p< .05 A =p< .I0 Figure 3. Male vs. female ratings by scenario for "how hurt,"Study 1. Sex Differences in Jealousy 89 Emotional Scenarios 7.92 7.29 6.74 6.32 5 4.74 4.42 -. -Female 8.7 8.34 7.57 7.47 6.28 5.49 5.79 Scenario 1 2 3 4 Secret love letter Deep emotional attachment Expensive bday present. Busy schedule 5 6 7 9 Inside joke Laughs at rival's joke Takes care of sick hend =p<.05, n =p < .10 Sexual Scenarios lo 0 1 2 3 4 5 6 7 -t Male 8.45 6.81 6.61 5.47 4.82 5.13 2.05 + Female 8.34 6.15 7 4.51 4.64 4.64 3.11 Scenario 1 Passionate sex with another 5 Sexual MTV games 2 Drunkone-night stand 6 Audition for lussing role in play 3 Dancing closely with stranger 7 Night out at strip club 4 Sensual massage 9 =p< .05 A =p< .10 Figure 4. Male vs. female ratings by scenario for "how jealous,"Study 1. Sex Differences in Jealousy 90 0 1 2 3 4 5 6 7 + Male 8.42 6.18 5.39 5.34 2.89 2.32 2.03 Female 9.55 7.87 7.02 7.19 4.54 2.87 3.26 Scenario 1 2 3 4 Secret love letter Deep emotional attachment Expensive bday present, Busy schedule 5 Inside joke 6 Laughs at rival's joke 7 Takes care of sick friend 9 =p< .05, A =p< .10 Sexual Scenarios I Male 8.95 7.78 4.5 1 4.76 1 3.47 1 3.37 1 1.78 / 1 -Female 1 9.47 1 8.23 1 6.09 1 5.15 / 3.89 1 3.68 1 2.74 ] Scenario 1 Passionate sex with another 5 Sexual MW games 2 Drunk one-night stand 6 Audition for lussing role in play 3 Dancing closely with stranger 7 Night out at strip club 4 Sensual massage + =p<.05 A =p<.10 Figure 5. Male vs. female ratings by scenario for "how sad,"Study 1. Sex Differences in Jealousy 91 8.89 6.74 4.5 5.18 2.66 2.13 2.29 Female 9.53 7.45 5.35 6 3.48 2.38 3.09 Scenario 1 2 3 4 Secret love letter Deep emotional attachment Expensive bday present Busy schedule 5 Inside joke 6 Laughs at rival's joke 7 Takes care of sick friend + =p < .05, A =p < .I0 Sexual Scenarios Scenario 1 Passionate sex with another 5 Sexual MTV games 2 Drunk one-night stand 6 Audition for kissing role in play 3 Dancing closely with stranger 7 Night out at strip club 4 Sensual massage 9 =p < .05 A =p< .10 Figure 6. Male vs. female ratings by scenario for "relationship threat,"Study 1. Sex Differences in Jealousy 92 Study 1: Sex Difference in "Overall Upset" 7 Sexual Infidelity Type 1. Male rn Female / Figure 7. Sex differences for "overall upset" by infidelity type, Study 1. Sex Differences in Jealousy 93 Study I :Sex Difference in "How Angw' Emotional Sexual Infidelity Type I m Male m em ale/ Figure 8. Sex differences for "how angry"by infidelity type, Study 1. Sex Differences in Jealousy 94 Study 1: Sex Difference in "How Hurt" Emotional Sexual Infidelity Type 1 Male Female I Figure 9. Sex differences for "how hurt"by infidelity type, Study 1. Sex Differences in Jealousy 95 Study I : Sex Difference in "How Jealous" Emotional Sexual Infidelity Type I Male Female / Figure 10. Sex differences for "how jealous"by infidelity type, Study 1. Sex Differences in Jealousy 96 Study 1: Sex Difference in "How Sad" Gnotional Sexual Infidelity Type Figure 11. Sex differences for "how sad"by infidelity type, Study 1. Sex Differences in Jealousy 97 Study I :Sex Difference in "Threat to Relationship" Infidelity Type Figure 12. Sex differences for "threat to relationshtp" by infidelity type, Study 1. Sex Differences in Jealousy 98 Study 1:Sex Difference Across all Measures Infidelity Type I Male IN Female 1 Figure 13. Sex differences across all dependent measures by infidelity type, Study 1. Sex Differences in Jealousy 99 Study 2: Sex Difference in "Overall Upset" Emotional Sexual Infidelity Type 1 rn Male Fernale / Figure 14. Sex differences for "overall upset"by infidelity type, Study 2. Sex Differences in Jealousy1 00 Study 2: Sex Difference in "How Angry" Emotional Sexual lnfide lity Type Figure 15. Sex differences for "how angry" by infidelity type, Study 2. Sex Differences in Jealousy1 01 Study2: Sex Difference in "How Hurt" Emotional Sexual Figure 16. Sex differences for "how hurt"by infidelity type, Study 2. Sex Differences in Jealousy102 Study 2: Sex Difference in "How Jealous" Emotional Sexual Infidelity Type I 1 a Male a Female Figure 17. Sex differences for "how jealous"by infidelity type, Study 2. Sex Differences in Jealousy1 03 Study2: Sex Difference in "How Sad" Emotional Sexual Infidelity Type I I rn Male rn Female Figure 18. Sex differences for "how sad"by infidelity type, Study 2. Sex Differences in Jealousy104 Study2: Sex Difference in "Threat to Relationship" 6 Emotional Sexual lnfidelity Type Figure 19. Sex differences for "relationship threat"by infidelity type, Study 2. Sex Differences in Jealousy1 05 Study 2: Sex Difference Across all Measures Emotional Sexual Infidelity Type Figure 20. Sex differences across all dependent measures by infidelity type, Study 2.