PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES IN MEN S SENSITIVITY TO FACIAL CUES OF MALE DOMINANCE

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1 Journal of Evolutionary Psychology, 2011, DOI: /JEP PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES IN MEN S SENSITIVITY TO FACIAL CUES OF MALE DOMINANCE CHRISTOPHER D. WATKINS 1, LISA M. DEBRUINE 1, ANTHONY C. LITTLE 2, DAVID R. FEINBERG 3, PAUL J. FRACCARO 1, BENEDICT C. JONES 1,* 1 School of Psychology, University of Aberdeen 2 School of Psychology, University of Stirling 3 Department of Psychology, Neuroscience and Behaviour, McMaster University Abstract. Recent research suggests that men may possess adaptations that evolved to counter strategic variation in women s preferences for masculine men. For example, women s preferences for masculine, dominant men are stronger during the fertile phase of the menstrual cycle than at other times and men demonstrate increased sensitivity to facial cues of male dominance when their partners are ovulating. Such variation in men s dominance perceptions may promote efficient allocation of men s mate guarding effort (i.e., allocate more mate guarding effort in response to masculine, dominant men in situations where women show particularly strong preferences for such men). Here, we tested for further evidence of adaptations that may have evolved to counter strategic variation in women s masculinity preferences. Men who reported having particularly feminine romantic partners demonstrated a greater tendency to attribute dominance to masculinized male faces than did men who reported having relatively masculine romantic partners. This relationship between partner femininity and men s sensitivity to facial cues of male dominance remained significant when we controlled for potential confounds (men s age, self-rated masculinity, reported commitment to their relationship, and the length of the relationship) and may be adaptive given that feminine women demonstrate particularly strong preferences for masculine, dominant men. While previous research has emphasized variation in women s masculinity preferences, our findings add to a growing body of research suggesting that sexual selection may also have shaped adaptations that evolved to counter such systematic variation in women s preferences for masculine, dominant men. Keywords: masculinity, dominance, individual differences, sexual conflict INTRODUCTION Masculine characteristics in men are positively correlated with indices of their mate quality (FINK and PENTON-VOAK 2002; GANGESTAD and SIMPSON 2000; JONES et al. 2008; LITTLE et al. 2002). For example, masculine characteristics are correlated with indices of men s long-term medical health (RHODES et al. 2003; THORNHILL * Corresponding author: BENEDICT C. JONES, School of Psychology, University of Aberdeen, Aberdeen, Scotland; ben.jones@abdn.ac.uk Akadémiai Kiadó, Budapest

2 70 CHRISTOPHER D. WATKINS et al. and GANGESTAD 2006), physical strength (FINK et al. 2007), reproductive potential (RHODES et al. 2005; HUGHES et al. 2004; PUTS 2005), and, in natural fertility populations, reported reproductive success (APICELLA et al. 2007). While these are qualities that women are likely to value in a mate, masculine characteristics in men are also associated with traits that may be undesirable in a long-term partner (FINK and PENTON-VOAK 2002; GANGESTAD and SIMPSON 2000; JONES et al. 2008; LITTLE et al. 2002). For example, masculine men are perceived as untrustworthy and emotionally cold (BOOTHROYD et al. 2007; PERRETT et al. 1998) and prefer to engage in short-term relationships, rather than long-term relationships, to a greater extent than their feminine peers (BOOTHROYD et al. 2008; RHODES et al. 2005). Thus, women who choose a masculine partner may incur both costs (e.g., low investment in relationship and offspring) and benefits (e.g., increased offspring health). Since women may weigh these benefits and costs in different ways depending on their personal attributes and circumstances, researchers have emphasized that one would expect systematic variation among women in the strength of their preferences for masculine men (FINK and PENTON-VOAK 2002; GANGESTAD and SIMP- SON 2000; JONES et al. 2008; LITTLE et al. 2002). One source of variation in women s masculinity preferences that has received a great deal of attention in the mate preference literature is changes in fertility during the menstrual cycle (for recent reviews see JONES et al and GANGESTAD and THORNHILL 2008). Women demonstrate increased attraction to masculine men during the most fertile phase of the menstrual cycle (i.e., around ovulation) when judging the attractiveness of men s odors (GRAMMER 1993), faces (JONES et al. 2005; PENTON-VOAK et al. 1999; WELLING et al. 2007), bodies (LITTLE et al. 2007), voices (FEINBERG et al. 2006; PUTS 2005, 2006), and behavioral displays (GANGESTAD et al. 2004). This increased attraction to masculine men around ovulation may function to increase offspring health, while preferences for more feminine men at other times may function to increase care, support and investment (see, e.g., JONES et al. 2008; PENTON-VOAK et al. 1999; GANGESTAD and THORNHILL 2008). While the findings described above suggest that women s mate preferences vary systematically during the menstrual cycle, more recent research has presented evidence that men may have evolved strategies to counteract these cyclic changes in women s mate preferences (BURRIS and LITTLE 2006; GANGESTAD et al. 2002; HASELTON and GANGESTAD 2006). For example, both GANGESTAD et al. (2002) and HASELTON and GANGESTAD (2006) found that women reported more frequent mate guarding (i.e., jealous and possessive behavior) by their partners around ovulation than at other times during the menstrual cycle. Complementing these findings for cyclic changes in partners mate guarding, BURRIS and LITTLE (2006) observed greater sensitivity to male facial cues of dominance among men whose own partners were ovulating than among men whose own partners were in non-fertile phases of the menstrual cycle. Such variation in sensitivity to cues of male dominance may reflect a counterstrategy that evolved to increase the efficiency and effectiveness of mate guarding behavior around ovulation when women demonstrate increased at-

3 PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES 71 traction to masculine, dominant men (BURRIS and LITTLE 2006). While previous studies suggest that men may possess adaptations that evolved to counteract cyclic changes in women s preferences for masculine men, psychological adaptations may also exist that have evolved to counteract other types of systematic variation in women s masculinity preferences. In addition to the effects of menstrual cycle phase, previous studies have reported positive correlations between women s preferences for masculine men and indices of their own femininity and attractiveness. For example, women s ratings of their own attractiveness are positively correlated with the strength of their preferences for masculine characteristics in men s faces (LITTLE et al. 2001; LITTLE and MANNION 2006) and voices (VUKOVIC et al. 2008). Other studies have found that women with feminine body shapes (i.e., a low waist-hip ratio) or vocal characteristics (i.e., relatively high voice pitch) demonstrate stronger preferences for masculine men than do women with relatively masculine body shapes (PENTON-VOAK et al. 2003; SMITH et al. 2009) or vocal characteristics (VUKOVIC et al. 2010). Stronger preferences for masculine men among feminine women (compared to relatively masculine women) may be adaptive if feminine women are better able to attract and/or retain masculine mates (LITTLE et al. 2001; PENTON-VOAK et al. 2003; SMITH et al. 2009; VUKOVIC et al. 2008; VUKOVIC et al. 2010). Given that particularly feminine women appear to demonstrate particularly strong preferences for masculine, dominant men, heterosexual men who consider their partners to be particularly feminine may be more sensitive to masculinity in men s faces and voices when assessing the dominance of potential same-sex competitors. Indeed, KRUGER (2006) found that masculine men were perceived to be more likely to knowingly hit on someone else s partner than their relatively feminine peers. Similarly, DIJKSTRA and BUUNK (2001) found that male competitors with masculine physical characteristics were perceived to be more dominant than relatively feminine competitors and also elicited greater jealousy in men. Moreover, HASELTON and GANGESTAD (2006) have previously found that attractive, feminine women report more frequent mate guarding by their partners than do relatively unattractive, masculine women. We might then expect that men with particularly feminine partners would be most attentive to cues of dominance in potential competitors. In the current study, we examined the relationship between men s ratings of their partner s femininity and their sensitivity to masculine characteristics when judging the dominance of other men s faces. Previous research has demonstrated that men tend to perceive masculinized versions of men s faces to be more dominant than feminized versions (e.g., JONES et al. 2010; MAIN et al. 2009; PERRETT et al. 1998). We predict that men with particularly feminine partners will be most likely to perceive masculine competitors as dominant. A positive correlation between the extent to which men attribute high dominance to masculine men and perceptions of their own partner s femininity would therefore present novel evidence for the existence of male strategies that may have evolved to counteract systematic

4 72 CHRISTOPHER D. WATKINS et al. variation in women s masculinity preferences. We examined the possible effects of perceived partner femininity, rather than attractiveness, in light of recent research suggesting that femininity of body shape in women, as measured by waist-hip ratio, is a better predictor of variation in women s preferences for masculine, dominant male faces than an attractive body shape that is not necessarily feminine, as measured by body mass index (SMITH et al. 2009). In addition to the above, we also investigated whether the predicted correlation between men s perceptions of partner femininity and their perceptions of other men s dominance was independent of the possible effects of several potential confounds (i.e., men s age, self-rated masculinity, reported commitment to their relationship, and the length of the relationship). Finally, we investigated the relationship between men s perceptions of partner femininity and their perceptions of masculinized versus feminized versions of women s faces. If greater sensitivity to cues of dominance in men s faces among men with particularly feminine partners functions, at least in part, to counteract systematic variation in women s preferences for masculine, dominant men, we would not necessarily anticipate a correlation between men s perceptions of partner femininity and their perceptions of other women s dominance. MATERIALS AND METHODS Face stimuli Following previous studies of systematic variation in perceptions of masculine and feminine faces (BUCKINGHAM et al. 2006; DEBRUINE et al. 2006; JONES et al. 2005, 2007; PENTON-VOAK et al. 1999; LITTLE et al. 2005; WELLING et al. 2007, 2008), we used prototype-based image transformations to objectively manipulate sexual dimorphism of 2D shape in digital face images. Although different methods for manipulating masculinity of face images have been used in some other studies (e.g., JOHNSTON et al. 2001), these methods have been shown to produce perceptual effects that are equivalent to those produced using the methods employed in our current study (DEBRUINE et al. 2006; DEBRUINE et al. 2010). First, male and female prototype (i.e., average) faces were manufactured using established computer graphic methods that have been widely used in studies of face perception (e.g., DEBRUINE et al. 2006; JONES et al. 2005, 2007; PENTON-VOAK et al. 1999; WELLING et al. 2007, 2008). Prototypes are composite images that are constructed by averaging the shape, color and texture of a group of faces, such as male or female faces. These prototypes can then be used to transform images by calculating the vector differences in position between corresponding points on two prototype images and changing the position of the corresponding points on a third image by a given percentage of these vectors (see ROWLAND and PERRETT 1995; TIDDEMAN, BURT and PERRETT 2001 for technical details).

5 PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES 73 Here, 50% of the linear differences in 2D shape between symmetrized versions of the male and female prototypes were added to or subtracted from face images of 20 young White male adults (age: M = 19.5 years, SD = 2.3 years) and 20 young White female adults (age: M = 18.4 years, SD = 0.7 years). This process creates masculinized and feminized versions of the individual face images that differ in sexual dimorphism of 2D shape and that are matched in other regards (e.g., identity, skin color and texture, ROWLAND and PERRETT 1995). Examples of masculinized and feminized face images are shown in Figure 1. Thus, 40 pairs of images were produced in total (each pair consisting of a masculinized and a feminized version of the same individual). Previous studies have demonstrated that this method for manipulating masculinity of 2D face shape affects perceptions of facial masculinity in the predicted manner (DEBRUINE et al. 2006; JONES et al. 2007; WELLING et al. 2007, 2008). Figure 1. Examples of masculinized (left) and feminized (right) face images used to assess men s perceptions of facial dominance in our study Procedure Seventy-five heterosexual male participants (Mean age = 27.6 years, SD = 7.00 years), all of whom reported having a long-term romantic partner, took part in the study.

6 74 CHRISTOPHER D. WATKINS et al. Participants completed a face perception test in which they were shown the forty pairs of faces (each pair consisting of a masculinized and feminized version of the same face) and were asked to indicate which face in each pair looked more dominant. For each pair of faces, participants also indicated whether they thought the more dominant face looked much more dominant, more dominant, somewhat more dominant, or slightly more dominant than the less dominant face. The order in which the pairs of faces were shown and the side of the screen on which a given version was presented were both fully randomized. This method for assessing perceptions of the dominance of masculinized versus feminized versions of faces has been used in previous studies of face perception (e.g., DEBRUINE et al. 2006; JONES et al. 2010; WELLING et al. 2007, 2008). In addition to completing the face perception test, each participant also rated the femininity of their romantic partner using a 1 (very masculine) to 7 (very feminine) scale (M = 4.87, SD = 1.66). Previous research has demonstrated that men can judge the femininity of women with a high degree of accuracy (i.e., can correctly identify the more feminine versions of women s faces and voices when presented pairs of masculinized and feminized stimuli at levels that are significantly greater than chance and are close to ceiling; FEINBERG et al. 2008; WELLING et al. 2008). Each participant also rated their own masculinity using a 1 (very feminine) to 7 (very masculine) scale (M = 4.40, SD = 1.17), rated their commitment to their romantic relationship using a 1 (not very committed) to 7 (very committed) scale (M = 5.55, SD = 1.54), reported the approximate date on which their relationship began, and reported their age. The mean length of relationship at the time of testing was 4.50 years (SD = 4.46 years). The order in which participants completed the questionnaire and face perception parts of the study was randomized across participants. The experiment was run online. Previous studies, including studies of dominance perception, have shown that online studies produce patterns of results for face perception that are virtually identical to those obtained in laboratory-based studies (e.g., JONES et al. 2005, 2007; MAIN et al. 2009; SENIOR et al. 1999a, 1999b). Initial processing of data Responses on the face perception test were coded using the following scale: 0 = feminized stimuli judged much more dominant than masculinized stimuli 1 = feminized stimuli judged more dominant than masculinized stimuli 2 = feminized stimuli judged somewhat more dominant than masculinized stimuli 3 = feminized stimuli judged slightly more dominant than masculinized stimuli 4 = masculinized stimuli judged slightly more dominant than feminized stimuli

7 PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES 75 5 = masculinized stimuli judged somewhat more dominant than feminized stimuli 6 = masculinized stimuli judged more dominant than feminized stimuli 7 = masculinized stimuli judged much more dominant than feminized stimuli For each participant, we calculated his average score for judgments of men s faces and his corresponding score for judgments of women s faces. Both of these variables were normally distributed (both Kolmogorov Smirnov Z < 0.64, both p >.81). RESULTS First, we used one-sample t-tests to compare men s scores for judgments of men s faces with chance (i.e., 3.5) and, in a separate analysis, to compare men s scores for judgments of women s faces with chance (i.e., 3.5). These analyses showed that Figure 2. The positive relationship between rated partner femininity and men s dominance sensitivity (rho =.30, N = 75, p =.009). On the Y-axis, 3.5 = chance

8 76 CHRISTOPHER D. WATKINS et al. Table 1. Inter-correlations among studies variables. Values show rho and, in brackets, two-tailed p. N = 75 for all correlations. Correlations where p <.05 are shown in bold dominance perceptions of women s faces partner femininity self-rated masculinity relationship length commitment to relationship participant age dominance perceptions of men s faces.54 (<.001).30 (.009).18 (.12).01 (.93).17 (.16).05 (.70) dominance perceptions of women s faces.06 (.64).13 (.25).16 (.16).15 (.20).14 (.22) partner femininity.20 (.09).11 (.35).10 (.41).08 (.49) self-rated masculinity.15 (.21).25 (.03).24 (.04) relationship length.12 (.31).73 (<.001) commitment to relationship.06 (.64) men perceived masculinized versions of both men s and women s faces to be more dominant than feminized versions (men s faces: t(74) = 10.26, p <.001, M = 4.63, SD = 0.95; women s faces: t(74) = 3.17, p =.002, M = 3.81, SD = 0.85). Next, we examined the inter-correlations among our variables (see Table 1). We used Spearman s tests because not all of the participant variables were normally distributed. As we had predicted, the extent to which men perceived masculinized versions of men s faces to be more dominant than feminized versions was positively correlated with the reported femininity of their romantic partners (rho =.30, N = 75, p =.009, Figure 2). By contrast, the corresponding correlation for judgments of women s faces was not significant (rho =.06, N = 75, p =.64). No other participant variables predicted dominance perceptions of either men s or women s faces (all absolute rho <.18, all p >.12). Finally, we conducted a regression analysis to investigate whether the positive relationship between the extent to which men perceived masculinized versions of men s faces to be more dominant than feminized versions and the reported femininity of their romantic partners remained significant when we controlled for the possible effects of the other participant variables. The score for judgments of men s faces was the dependent variable in this analysis and rated partner femininity, selfrated masculinity, participant age, relationship length, and commitment to relation-

9 PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES 77 ship were independent variables. Note that the dependent variable in this analysis was normally distributed, which is a requirement for regression analyses, and that regression analyses do not require independent variables to be normally distributed (HAYS 1965). This analysis revealed a significant positive relationship between the extent to which men perceived masculinized versions of men s faces to be more dominant than feminized versions and the reported femininity of their romantic partner (t = 2.70, standardized beta =.31, p =.009). There were no other significant relationships or relationships that approached significance (all absolute t < 1.05, all absolute standardized beta <.16, all p >.30). A corresponding analysis for judgments of women s faces revealed no significant relationships (all absolute t < 1.45, all absolute standardized beta <.24, all p >.15). DISCUSSION Consistent with previous research on perceptions of men s dominance (BOOTHROYD et al. 2007; DEBRUINE et al. 2006; JONES et al. 2010; MAIN et al. 2009; PERRETT et al. 1998), masculinized versions of other men s faces were generally perceived to be more dominant than feminized versions. Although this finding presents further evidence that masculine men are generally perceived to be more dominant than feminine men, further analyses of men s dominance judgments revealed systematic variation in the extent to which men with masculine characteristics were perceived as particularly dominant. As we had predicted, femininity ratings of men s romantic partners were positively correlated with the extent to which they perceived masculinized male faces to be more dominant than feminized versions. Moreover, this relationship remained significant when we controlled for a number of potential confounds (i.e., men s age, self-rated masculinity, reported commitment to their relationship, and the length of the relationship). Collectively, these findings support our prediction that men who reported having particularly feminine romantic partners would be particularly sensitive to facial cues of dominance in other men. No equivalent relationship was observed for judgments of women s faces. This latter finding suggests that our findings for men s faces cannot be explained by a general response bias, whereby some men may have simply been more willing to use extreme points on the response scales than other men were, or individual differences in the degree of gender stereotyping among men. Many previous studies have reported that women demonstrate stronger attraction to masculine men around ovulation than at other points during the menstrual cycle, potentially increasing offspring health (for recent reviews see JONES et al and GANGESTAD and THORNHILL 2008). Recent research has also suggested that men show increased sensitivity to male facial cues of dominance when their own partners are ovulating, potentially reflecting a strategy that evolved to counteract cyclic variation in women s masculinity preferences by increasing the efficiency and effectiveness of mate guarding behavior around ovulation (BURRIS and LITTLE

10 78 CHRISTOPHER D. WATKINS et al. 2006). Our current findings show that men who report having particularly feminine romantic partners are particularly sensitive to facial cues of dominance in other men. Studies have previously demonstrated that feminine women show stronger preferences for masculine, dominant men than do relatively masculine women (PENTON-VOAK et al. 2003; SMITH et al. 2009; VUKOVIC et al. 2010). By showing greater sensitivity to cues of dominance in other men, men with particularly feminine partners may therefore be better able to use their mate guarding effort to guard against approaches from masculine, dominant men, who feminine women consider to be particularly attractive and who appear to show particularly strong preferences for feminine women (JONES et al. 2007; LITTLE et al. 2001; PENTON-VOAK et al. 2003; SMITH et al. 2009; VUKOVIC et al. 2008; WELLING et al. 2008). Here, we assessed partner femininity by having men report how feminine their own partners were. Analogous to how subjective impressions of women s own attractiveness have previously been shown to predict reported mate guarding by male partners (HASELTON and GANGESTAD 2006) and individual differences in masculinity preferences (LITTLE et al. 2001; VUKOVIC et al. 2008), here we show that subjective impressions of their partner s femininity predict individual differences in men s sensitivity to cues of male dominance. Nonetheless, we acknowledge that it remains to be seen whether our findings for self-reported partner femininity generalize to more objective measures of the femininity of men s long-term partners (e.g., measures of body shape, facial femininity, or voice pitch). Investigating whether men s own perceptions of their partner s femininity or these more objective assessments are more important for variation among men in their perceptions of other men s dominance is an important issue for future research that may shed light on the mechanisms and processes through which partner characteristics predict dominance sensitivity. For example, it may shed light on whether the observed variation in men s behavior is shaped by their own perceptions of their romantic partner, other men s behavior towards their partner, or both of these factors. A further issue that emerges from our study but remains unresolved is the mechanisms and processes that lead to the positive relationship between variation in men s sensitivity to cues of male dominance and partner femininity that was observed in our study. One possibility is that men demonstrate facultative changes in their sensitivity to dominance when they attain a particularly feminine or masculine partner. Alternatively, sensitivity to cues of male dominance may be correlated with characteristics that feminine women, in particular, value in potential mates. Longitudinal research tracking men s sensitivity to cues of male dominance when they acquire new partners may shed light on this issue. Importantly, however, we note here that greater sensitivity to male cues of dominance among men with feminine partners could function to promote efficient allocation of mate guarding effort equally well regardless of whether the relationship between dominance sensitivity and partner femininity is a consequence of a facultative response to the perceived femininity of one s current romantic partner or a more trait-like response among men who are particularly likely to have highly feminine partners at any given time.

11 PERCEPTIONS OF PARTNER FEMININITY PREDICT INDIVIDUAL DIFFERENCES 79 In summary, our findings show that men s femininity ratings of their romantic partners predict the extent to which they perceive masculinized male faces to be more dominant than feminized versions. In other words, men reporting particularly feminine romantic partners appear to be particularly sensitive to facial cues of other men s dominance, potentially reflecting individual differences in dominance perception that evolved to counteract condition-dependent masculinity preferences in women. Previous research on human mating strategies has emphasized potentially adaptive variation in women s mate preferences. By contrast with this emphasis on variation in women s mate preferences, our findings add to a growing body of research (BURRIS and LITTLE 2006; GANGESTAD et al. 2002; HASELTON and GANG- ESTAD 2006) suggesting that sexual selection may also have shaped adaptations that increase the effectiveness of mate-guarding behaviors in men and compensate for adaptive variation in women s mate preferences. ACKNOWLEDGEMENTS This work was partly supported by a 6th Century Studentship from the University of Aberdeen. REFERENCES APICELLA, C. L., FEINBERG, D. R. & MARLOWE, F. W. (2007): Voice pitch predicts reproductive success in male hunter-gatherers. Biology Letters, 3, BOOTHROYD, L. G., JONES, B. C., BURT, D. M., DEBRUINE, L. M. & PERRETT, D. I. (2008): Facial correlates of sociosexuality. Evolution and Human Behavior, 29, BOOTHROYD, L. G., JONES, B. C., BURT, D. M. & PERRETT, D. I. (2007): Partner characteristics associated with masculinity, health and maturity in male faces. Personality and Individual Differences, 43, BUCKINGHAM, G., DEBRUINE, L. M., LITTLE, A. C., WELLING, L. L. M., CONWAY, C. A., TIDDE- MAN, B. P. & JONES, B. C. (2006): Visual adaptation to masculine and feminine faces influences generalized preferences and perceptions of trustworthiness. Evolution and Human Behaviour, 27, BURRIS, R. P. & LITTLE, A. C. (2006): Effects of partner conception risk phase on male perception of dominance in faces. Evolution and Human Behaviour, 27, DEBRUINE, L. M., JONES, B. C., LITTLE, A. C., BOOTHROYD, L. G., PERRETT, D. I., PENTON- VOAK, I. S., COOPER, P. A., PENKE, L., FEINBERG, D. R. & TIDDEMAN, B. P. (2006): Correlated preferences for facial masculinity and ideal or actual partner s masculinity. Proceedings of the Royal Society of London B, 273, DEBRUINE, L. M., JONES, B. C., SMITH, F. G. & LITTLE, A. C. (2010): Are attractive men s faces masculine or feminine? The importance of controlling confounds in face stimuli. Journal of Experimental Psychology: Human Perception and Performance, 36, DIJKSTRA, P. & BUUNK, B. P. (2001): Sex differences in the jealousy-evoking nature of a rival s body build. Evolution and Human Behavior, 22,

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