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Unit: HPS121: Introduction to Psychology B
Topic: Jealousy: Testing Predictions Of The Evolutionary Model
Name: Mark Brown
Student No: 100201868
For : Sarah Phillips
Tute time: Friday 11 - 12

Abstract
Evolutionary psychology predicts that men and women will differ in the jealousy evoked by sexual versus emotional infidelity. While evidence for these differences have been found, critics argue that these results may be the cause of gender differences in how the survey question is perceived. 326 undergraduate students were surveyed in an attempt to find further evidence for either the perceptual differences or the evolutionary model. The results suggested that the perceptual differences do not account for findings of the previous research. However, not all of the data supported the evolutionary predictions.

Jealousy: Testing Predictions Of The Evolutionary Model

Until recently, the significance of sexual jealousy may have been overlooked by research psychologists (Buunk, Angleitner, Oubaid, & Buss, 1996). Jealousy has been assumed to be the by-product of other basic emotions (Bunnk et al., 1996) or a pathological phenomenon (Wilson & Daly, 1996). However, recent lines of research have proposed that jealousy may be a specific capacity selected for by evolution. Research in this area provides an opportunity to test certain predictions made on this basis, and is an opportunity to refine a branch of evolutionary theory (Buss, 1995). Further understanding of jealousy may also be useful in forensic psychology, treatment, and counselling given the links between male sexual jealousy and cases of wife battering and homicide (Wilson & Daly, 1996).

From an evolutionary perspective the capacity for jealousy is viewed as an adaptation to problems faced in human evolutionary history (Buss, Larsen, Westen, & Semmelroth, 1992). In species with internal female fertilisation, including humans, only the female can be certain that the child she provides for is her genetic offspring (Buss et al., 1992). As a consequence of paternity uncertainty, males risk investing effort and resources on children that are not their own. Considering that human males invest heavily in their children relative to other species, Buss et al. (1992) have reasoned that in men this evolutionary pressure would strongly select for mechanisms that would prevent cuckoldry. For females, infidelity threatens partial or complete loss of male resources to other women (Buss et al., 1992). Sensitivity and concern for signs that foreshadow the loss of a mate’s investment (signs of a deep emotional attachment developing) would therefore be particularly adaptive for women. Jealousy is thought to be a specific mechanism that solves these problems for both sexes.

Based on this model, Buss et al. (1992) conducted 3 studies, testing the hypothesis that men and women will differ in the amount of distress evoked by sexual versus emotional infidelity. Men were predicted to show more distress over sexual infidelity while women were predicted to find emotional infidelity more upsetting. In two of the studies participants were asked a forced choice question. They were asked to imagine being confronted with either the sexual or emotional infidelity of a partner and to specify which scenario was more distressing. These studies found significant sex differences in the hypothesised direction. A separate study, measuring physiological responses to these scenarios showed similar differences.

Cross-cultural studies using the forced-choice methodology have replicated these findings (Buunk et al., 1996). The predicted sex differences were found in samples from the United States, Germany, and the Netherlands, however, the effect sizes varied. This cross cultural data can be seen as demonstrating that the differences are species wide - an important feature for an evolutionary model (Buss, 1995). The different effect sizes suggest that cultural input may a role in mediating the jealousy mechanism. Critics of the evolutionary model, however, have questioned the interpretations of the data gathered using this paradigm. Harris and Christenfeld (1996) point out that ranging from approximately half the men in the US study to three quarters in the Dutch study do find emotional infidelity more distressing. The evolutionary theory does not explain this phenomenon.

DeSteno and Salovey (1996) have argued that because the research conducted was correlational in nature the results may have been confounded by other variables that correlate with sex. DeSteno and Salovey (1996) hypothesised that participants may perceive one type of infidelity as implying the other; the option that best offers this 'double-shot', therefore, is more likely to be chosen. If men and women differ in their perceptions of the 'double-shot' then this could account for the sex difference found by Buss et al (1992). Variability in how the forced-choice questions are interpreted could also explain the variation within sex groups (DeSteno & Salovey, 1996).

To test the 'double-shot' hypothesis, DeSteno and Salovey (1996) replicated the forced-choice methodology but included an additional measure of the perceived nonindependance of the two options. The results showed that women viewed emotional infidelity as implying sexual infidelity, where as men perceived both types as either independent or equally dependant; as predicted this corresponded to the forced choice data. This new variable was shown to be a better predictor of participants’ response to the forced choice questions than sex.

Using continuous measurements, a separate study failed to reproduce the forced-choice differences (DeSteno & Salovey, 1996), although these results were limited by a small sample size.
DeSteno and Salovey's (1996) results support an alternative to the evolutionary interpretation, and they also suggest that the forced-choice methodology may produce misleading data. In an attempt to resolve some of these issues the following research questions were formulated:

1. Do males and females differ with respect to how they interpret "emotional" and "sexual" infidelity?

2. If we remove the 'double-shot' from the questions posed by Buss et al. (1992) will we still find the sex-differences in responding that Buss et al. (1992) argued were supportive of the evolutionary framework?

3. Can the findings of Buss et al. (1992) be repeated using continuous rather than forced-choice methodology in a larger sample than that investigated by DeSteno and Salovey (1996)?

To investigate these questions, an online survey was made available for a group of over 900 undergraduate psychology students. The participants were asked to imagine discovering an instance of either sexual or emotional infidelity by a real or hypothetical partner. They responded to these scenarios in forced-choice format and on a continuous 7-point scale. In order to control for the 'double-shot' effect, forced-choice questions clearly stated that the alternative type of infidelity was not implied. Participants also rated how likely it would be that their partner could experience each infidelity type independently of the other.

Following from DeSteno and Salovey's (1996) argument, it is hypothesised that the likelihood of a partner forming a deep emotional attachment to someone without becoming sexually attracted to them will be rated lower by women than by men (item 18.3 on the survey).

Since these differences in perception appear to account for the sex differences in choice of infidelity type, it is expected that males and females will respond to the reformulated forced-choice options in similar proportions (item 15).

When responding to each infidelity type on a series of likert scales (items 17 and 18) it is predicted that men will not rate sexual infidelity as more distressing than emotional infidelity, and women will not rate emotional infidelity as more distressing than sexual infidelity.
Method

Participants

Participants were 326 first year psychology students (52 males, 274 females) who volunteered to complete the survey. The mean age was 23.03 years (SD=7.90)

Materials and Apparatus

Participants completed the survey via the Deakin University website using a computer with Internet access and a standard web browser. Questions were largely based on those used in previous studies (Buss et al., 1992; Desteno & Salovey, 1996) and consisted of 25 questions (See Appendix A for a copy of the survey).

Procedure

Students studying Introduction to Psychology B were invited to complete the survey online; the link was made available from within the unit's website. Participation was voluntary and anonymous.
Participants completed a version of the survey worded appropriately for their gender. They were also randomly assigned (based on date of birth) to one of two versions in which the order of infidelity was reversed.

Some questions included sub-questions, bringing the total number of questions to 48.

The Deakin University Human Research Ethics Committee approved these procedures.

Results

In order to test Hypothesis 1, males’ and females’ responses to Question 18.3 on the survey: ‘How likely do you think that it could be that your partner could form a deep emotional attachment with another person without also being sexually attracted to that person’ were compared using an independent samples t-test. Participants answered the question on a likert scale ranging from 1= (extremely unlikely) to 7 (extremely likely). Mean ratings made by each sex are provided in Table 1.

Mean SD
Males 3.87 1.70

Females 3.49 1.68

Table 1. Mean ratings made by men and women for question 18.3

While the data presented in Table 1, with males scoring higher than females on the item, is suggestive of the hypothesised effect, the difference was not significant t(324) =1.48, p>.05. As such, females and males did not differ in the likelihood that they would report that their partners could become emotionally involved with another person without also becoming sexually attracted to that person.
In response to the forced-choice formatted question with the ‘double-shot’ removed, 70.3% of males reported more distress about sexual infidelity, while the slight majority of females, 57.3%, reported more distress about the possibility of a partner’s emotional infidelity. Application of χ2 analysis indicated that this pattern represented a significant relationship between sex and responding χ2 (1, 325)=13.42, p<.05. This ¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬did not support the hypothesis that males and females would have similar rates of responding if the ‘double-shot’ was removed.

Data obtained for the purposes of addressing research question 3, is presented in Figure 1. Examination of Figure 1 indicates that, for males, emotional infidelity in a partner was rated as less distressing than sexual infidelity. Statistical analysis via paired samples t-test indicated that this difference was significant; this result does not support the hypothesis that men would not rate sexual infidelity higher. For females, emotional infidelity in a partner was rated as less distressing than sexual infidelity. Statistical analysis via paired samples t-test indicated that this difference was significant, supporting the hypothesis that women would not rate emotional infidelity as more distressing. Further examination of the results displayed in Figure 1 indicates that, overall, compared with men, women displayed more distress to both types of infidelity.

Figure 1. Levels of distress over sexual vs emotional infidelity reported by male and female participants on the continuous measures.

Discussion

In contradiction of the first hypothesis, women were no more likely to perceive emotional infidelity as implicating sexual infidelity. The second hypothesis was also unsupported, as a significant relationship between sex and response to the forced-choice measure was found, even with the 'double-shot' removed. However, the final hypothesis was partially supported. While the continuous measure showed that men rated sexual infidelity as more distressing, women also rated sexual infidelity as the more distressing scenario.

The results for the first research question undermine the 'double-shot' hypothesis. The inability to replicate the perceptual differences found by DeSteno and Salovey (1996) suggest that the original forced-choice results found by Buss et al. (1992) were not confounded by this variable.
This is supported by the differences found on the reformulated forced-choice question. With the potential for a double-shot' removed the percentage of men choosing sexual infidelity was even greater than in the original study (Buss et al., 1992). While the percentage of women choosing emotional infidelity is not as large as the original study (Buss et al., 1992), it is still supportive of the evolutionary predictions. The differences in effect size between this study and the previous research may be due to the changes to the phrasing of the question, or may reflect cultural differences.

These findings are consistent with the argument that the differences are a direct product of biological sex (and therefore supportive of the evolutionary model). However, it should be noted that they do not prove causation. The results are still limited by the impossibility of randomly assigning the participants to the independent variable (gender) (DeSteno & Salovey, 1996).

Results on the continuous measures of jealousy do not appear consistent with the findings of Buss et al. (1992). While men did rate sexual infidelity as more distressing than emotional infidelity, the results for women appear to contradict the forced-choice results for this and previous studies.
One possible explanation for this discrepancy may be that female participants who chose sexual infidelity as the more distressing scenario may have rated it as significantly more distressing than the alternative; the other female participants may have chosen emotional infidelity because it was only slightly more of a concern. As the forced-choice measure is not sensitive to the magnitude of distress, the strong reaction of a minority would not be reflected in the results. However, when measured on a continuous scale, the average ratings for sexual infidelity could be boosted by a smaller number of high ratings.

Future studies could examine this possibility by expressing the results of the continuous measures in an alternative format. If the data is analysed in terms of which infidelity type each participant rated higher, then these results could be expressed as the proportion of men and women who found each infidelity type more distressing. In this way, the continuous measures can be better compared with the forced-choice data.

Overall this study provides strong evidence against the 'double-shot' hypothesis. However the results of the continuous measure create uncertainty about the implications of the results for the evolutionary model. The continuous measure may or may not be supportive of the predictions. Further research is needed to clarify this issue as well as to test the generaliseability of these findings cross-culturally and in a non-student sample.

References

Buss, D.M. (1995). Evolutionary psychology: A new paradigm for psychological science, Psychological Inquiry, 6, 1-30.
Buss, D.M., Larsen, R.J, Westen, D. & Semmelroth, J. (1992). Sex differences in jealousy: physiology and psychology. Psychological Science, 3, 251-255.
Buunk, B.P., Angleitner, A., Oubaid, V., Buss, D.M. (1996). Sex differences in jealousy in evolutionary and cultural perspective: test from the Netherlands, Germany, and the United States. Psychological Science, 7, 359-363.
DeSteno, D.A. & Salovey, P. (1996). Evolutionary origins of sex differences in jealousy?: the “fitness” of the model. Psychological Science, 7, 367-372.
Harris, C.R. & Christenfeld, N. (1996). Jealousy and rational responses to infidelity across gender and culture. Psychological Science, 7, 378-379.
Wilson, M.I. & Daly, M. (1996) Male sexual proprietariness and violence against wives. Current Directions in Psychological Science, 5, 2-7.