Sex Differences in Jealousy 1
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
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.
Sex Differences in Jealousy 3 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...
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
Sex Differences in Jealousy 5
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&
Sex Differences in Jealousy 7
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
Sex Differences in Jealousy 9
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
Sex Differences in Jealousy 1 1
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
Sex Differences in Jealousy 13
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
Sex Differences in Jealousy 15
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
Sex Differences in Jealousy 17
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
Sex Differences in Jealousy 19
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
Sex Differences in Jealousy 21
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
Sex Differences in Jealousy 23
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 5 1 % 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.
Sex Differences in Jealousy 25
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
Sex Differences in Jealousy 27
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
Sex Differences in Jealousy 29
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
Sex Differences in Jealousy 3 1
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
Sex Differences in Jealousy 33
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.
Sex Differences in Jealousy 35
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
Sex Differences in Jealousy 39
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.
Sex Differences in Jealousy 39
"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
