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Male stature is directly related to dominance and has a significant impact on reproductive success. Throughout the animal kingdom, larger males are more likely to win fights and to attain dominance (e.g., Goodall, 1986, McElligott et al., 2001, Schuett, 1997). Even the giraffe's long neck—often cited as a classic example of an adaptation for survival—may have evolved in part to facilitate dominance competitions (Simmons & Scheepers, 1996). Thus, males in many species may, through dominance, obtain and monopolize access to females.
In humans, who walk upright, height is one of the first features that others notice and is associated with status. For instance, one study found that full professors were 0.47 in. taller than associate professors, who were 0.26 in. taller than assistant professors, who were 1.24 in. taller than the average nonacademic (Hensley, 1993). The reproductive advantages of height for males are apparent in the female preference for taller males (Kurzban & Weeden, 2005, Pawlowski, 2003, Shepperd & Strathman, 1989). Indeed, taller men receive more replies to dating announcements (Pawlowski & Koziel, 2002), have more physically attractive girlfriends (Feingold 1982), and have more reproductive success (Mueller & Mazur, 2001, Nettle, 2002a, Nettle, 2002b, Pawlowski et al., 2000). Given that height is highly heritable (one recent estimate—in a study using the Danish Twin Registry—found heritability coefficients of .69 for men and .81 for women; Schousboe et al., 2004), females choosing tall males are more likely to have tall male offspring, who in turn would be preferred by females.
Underlining the greater attractiveness of taller males to females, there is evidence suggesting that height may serve as an indicator of good genes. First, there is evidence that height is correlated with cognitive abilities (Case & Paxon, 2006), which translates into higher wages (e.g., Judge & Cable, 2004, Loh, 1993). Second, paralleling other good-genes indicators (e.g., Gangestad et al., 2004, Thornhill & Gangestad, 1999), women desire a larger partner-to-self height discrepancy when they are in the fertile phase of the ovulatory cycle and when they are considering partners for a short-term relationship (Pawlowski & Jasienska, 2005). In addition, male height has been found to be correlated with physical health and with morphological symmetry (Manning, 1995, Silventoinen et al., 1999). There is some evidence that shorter people may live longer than taller people if environmental factors are compatible with a small body size (e.g., Samaras et al., 2003, Weeden & Sabini, 2005). However, this does not contradict the evidence that height indicates good genes for men, as height could contribute to fitness at reproductive ages while imposing costs at later ages.
In the present research, we examined the relationship between height and jealousy. Jealousy is an emotional and motivational response that has been hypothesized to serve the function of protecting the pair bond from rivals (Buunk et al., 2007, Daly et al., 1982). Like many evolved mechanisms, jealousy is expected to be functionally flexible: It is a costly response that should be activated most strongly when it is most functional, such as when it may reduce the likelihood of losing the mate or—in the case of males—the likelihood of investing in another's male's offspring due to infidelity of the mate. Height may plausibly influence male jealousy via two routes. First, given the association between height and attractiveness, partners of taller males may have fewer reasons to cheat, reducing the need for mate-guarding and jealousy. Second, given the association between height and dominance, taller males may more successfully deter rivals, reducing the need for mate-guarding and jealousy.
For women, the relationship between height and jealousy may be different because it seems that women of medium height seem to be the healthiest and most attractive to men. Very short and very tall women are more prone to illnesses than women of average height (Silventoinen et al., 1999), and very tall women are also more likely to develop depression symptoms (Bruinsma et al., 2006). Men consistently tend to prefer women who are shorter than they are, although not too short (Pawlowski, 2003, Pawlowski & Koziel, 2002), and shorter women tend to be more symmetrical (Manning, 1995). Indeed, women of approximately average height have higher reproductive success (Nettle, 2002b). The apparent curvilinear relationship between female height and attractiveness to males would suggest that there would also be a curvilinear relationship between women's height and jealousy. Therefore, we hypothesized that women of around average height may be least jealous and that women who are increasingly taller or shorter than average may be more jealous.
Nevertheless, there is reason to assume that there will also be a negative linear relationship between jealousy and height among women because height may affect women's fighting ability and dominance. The importance of physical fights in competition among women has often been underestimated, but it does exist. In a study of polygynous societies, Burbank (1987) observed that co-wives may intrasexually compete for food and money, paternal care for their offspring, and offspring's inheritance. In 61% of the 137 cultures she analyzed, women engaged in physical aggression, typically fighting with other women over men.
Study 1 was a preliminary investigation in which we used a global measure of jealousy for a first test of our hypotheses. In testing these hypotheses, we also examined the effect of body mass index (BMI). BMI is negatively related to both men's and women's attractiveness as potential partners (Kurzban & Weeden, 2005), is heritable (Allison et al., 1996), and is related to health and reproductive success, especially among women (e.g., Pawlowski & Dunbar, 2005). Thus one might expect that women with higher BMI would be more jealous.
2. Study 1
2.1.1. Participants and procedure
We used a sample of 100 men and 100 women described by Buunk (1997) in an article reporting distinct hypotheses and results not mentioned here. Participants were heterosexual individuals in close relationships recruited through an announcement on Dutch national television. Because more women than men responded, Buunk (1997) created matched samples for men and women using a random sampling procedures (for additional details about this sample, see Buunk, 1997). The mean age was 33 years (range, 15–76). The average heights were, for men, mean=180.74 cm (range, 164–200; S.D.=7.98), and for women, mean=168.19 cm (range, 152–184, S.D.=7.02). We also computed BMIs.
Global jealousy was assessed with a single question: “In general, how jealous are you in your current relationship?” The possible responses were (1) “not jealous,” (2) “hardly jealous,” (3) “a little bit jealous,” (4) “quite jealous,” (5) “very jealous,” and (6) “morbidly jealous.” Men (mean=3.05, S.D.=1.51) and women (mean=3.37, S.D.=1.51) did not differ in their responses (p=.14). In addition, we assessed individuals' perceptions of their partner's extrapair sexual interest with the following question: “To what extent do you think your partner is sexually interested in individuals of the opposite sex?” (1=not at all, 5=very much). Men (mean=1.92, S.D.=.94) and women (mean=2.13, S.D.=1.07) did not differ in their responses (p=.16).
2.2. Results and discussion
Regression analyses were used to test for linear and quadratic effects. Among men (Fig. 1), there was a negative linear relationship between height and jealousy [F(1,98)=4.73, r=−.22, p=.032] but no quadratic relationship [F(2,97)=2.40, p=.096]. Among women (Fig. 2), there was a nonsignificant negative linear relationship between height and jealousy [F(1,96)=2.97, r=−.17, p=.088] but a significant quadratic relationship [F(2,95)=4.35, p=.016].
Fig. 1. Linear relationship between men's height and self-reported jealousy.
Fig. 2. Quadratic relationship between women's height and self-reported jealousy.
Among men, height was not related with perceptions of their partner's sexual interest in others (F's≤.13, p's≥.72). Among women, there was a linear relationship between height and perceptions of their partner's sexual interest in others [F(1,94)=6.83, r=−.26, p=.010], which was qualified by a quadratic relationship [F(2,93)=3.76, p=.027]. Shorter women indicated higher perceptions of their partners' sexual interest in other women; however, somewhat paralleling the findings for jealousy, the negative relationship attenuated as height increased (Fig. 3). Furthermore, among men, perceptions of partner's interest in others were not related to jealousy (r=.02, p=.87); among women, there was a substantial positive correlation between perceptions of partner's interest in others and jealousy (r=.35, p<.001).
Fig. 3. Quadratic relationship between women's height and perceptions of partner's sexual interest in others.
Finally, we examined whether participants' BMIs were related to jealousy and perceptions of partner's interest in others. The BMIs were at normal levels: for men, mean=23.54 (S.D.=4.14), and for women, mean=22.72 (S.D.=3.57). There was no evidence that BMI had any effect on jealousy for either men or women (F's≤1.37, p's≥.26), suggesting that the impact of height on jealousy is independent of any impact that weight may also have on jealousy. However, BMI conflates fatness and muscularity, so we cannot conclude that fatness or muscularity does not affect jealousy.
Although preliminary, the results of Study 1 supported the predictions. Taller men tended to be less jealous, and the tallest men were the least jealous. In contrast, very short and very tall women tended to be more jealous, and women of approximately average height were the least jealous. The underlying mechanism among women was illuminated by a curvilinear relationship between women's height and perceptions of their partner's interest in others—average-height women were less likely to perceive potential infidelity in their partners.
3. Study 2
Study 1 had some limitations. Specifically, rather than assessing jealousy, the measure may have assessed how often participants' partners exhibited behavior that provoked jealousy. This seems unlikely for men as there was no correlation between jealousy and the perceived partner's interest in others, but it may have occurred among women as there was a positive correlation between these two variables. This suggests that men and women may have interpreted the question differently. To circumvent this problem in Study 2, we assessed jealousy within a well-defined and vivid scenario—intensive mutual flirting of one's partner and a rival at a party—that has been used previously (Dijkstra & Buunk, 1998, Dijkstra & Buunk, 2002). We used a scale that assesses how much jealousy rivals with a particular characteristic would evoke (Dijkstra & Buunk, 2002). The characteristics represented the dimensions of social influence, physical attractiveness, physical dominance, seductive behavior, and social status. As male jealousy has been found to be particularly evoked by the social influence, physical dominance, and social status of a rival, we expected height to have a linear effect on jealousy especially in response to these characteristics. As female jealousy has been found to be particularly evoked by the physical attractiveness of a rival, we expected height to have a curvilinear effect on jealousy especially in response to attractiveness.
3.1.1. Participants and procedure
Participants were 119 male and 230 female students at the University of Valencia. Professors from various fields collaborated in collecting the data after class. The mean age was 22 years (range, 18–30). Forty-six percent were in a steady relationship, 10% had a stable relationship, 4% was married or cohabiting, and 38% did not have a steady relationship (2% unknown). The fields of study included social and behavioral sciences (10%), physiotherapy (16%), physical activity sciences (13%), labor sciences (14%), history (12%), tourism (15%), biology (15%), and others (5%). The average heights were, for men, mean=178.22 cm (range, 157–197, S.D.=7.49), and for women, mean=164.87 cm (range, 150–180, S.D.=5.99). We also computed the BMIs.
Male participants were asked to imagine that the following situation was happening to them (female participants received exactly the same scenario and questionnaire except for the sex of their partner and rival):
You are at a party with your girlfriend and you are talking with some of your friends. You notice your girlfriend across the room talking to a man you do not know. You can see from his face that he is very interested in your girlfriend. He is listening closely to what she is saying and you notice that he casually touches her hand. You notice that he is flirting with her. After a minute, your girlfriend also begins to act flirtatiously. You can tell from the way she is looking at him that she likes him a great deal. They seem completely absorbed in each other.
Participants were then presented with a number of characteristics and were asked how jealous they would feel on a five-point scale (1=not at all, 5=very strongly) if the rival possessed them (in relation to the self). The characteristics were formulated by Dijkstra and Buunk (2002) after conducting an extensive interview study. On the basis of factor analyses in student as well as community samples, Dijkstra and Buunk (2002) constructed five subscales that were also used in the present study: social influence (labeled social dominance by Dijkstra & Buunk, 2002; 17 items; Cronbach's α=.93; e.g., is more charismatic, is more self-confidence, has more ascendance, is a better talker, is more popular); physical attractiveness (eight items; α=.93; e.g., is more slender, has a better figure, has a more attractive body); seductive behaviors (seven items; α=.80; e.g., dresses more revealingly, behaves more provocatively, is more of a seducer); physical dominance (eight items; α=.87; e.g., is more muscular, is more athletic, has a heavier build); and social status (four items; α=.80; e.g., has a better job, has more money, has a better education).
3.2. Results and discussion
Among men, the results were largely consistent with the hypothesis (Fig. 4). There was a negative linear relationship between height and jealousy for social influence [F(1,116)=4.00, r=−.18, p=.048] and physical dominance [F(1,116)=4.79, r=−.20, p=.031]; neither quadratic trend was significant (p's≥.085). There was also an unpredicted negative linear relationship for physical attractiveness [F(1,116)=5.33, r=−.21, p=.023]; the quadratic effect was not significant (p=.074). All remaining effects were not significant (F's≤2.67, p's≥.11). In sum, taller men tended to be less jealous—and shorter men more jealous—when confronted with socially dominant, physically dominant, and physically attractive rivals (but not when confronted with rivals characterized by high social status or seductive behavior).
Fig. 4. Linear relationships between men's height and self-reported jealousy in response to a (A) socially influential, (B) physically dominant, and (C) physically attractive rival.
The pattern of results differed among women (Fig. 5). There was a negative linear relationship between height and jealousy for physical attractiveness [F(1,225)=6.37, r=−.17, p=.012], which was qualified by a quadratic relationship [F(2,224)=3.28, p=.040]. Very tall and very short women were relatively more jealous than would be expected on the basis of just a linear trend. In addition, there were negative linear relationships and quadratic relationships for “masculine” rival characteristics—physical dominance [linear effect: F(1,225)=8.73, r=−.19, p=.003; quadratic effect: F(2,224)=5.07, p=.007] and social status (linear effect: F(1,225)=6.13, r=−.16, p=.014; quadratic effect: F(2,224)=4.81, p=.009). However, these quadratic effects were opposite to that for physical attractiveness, with women of average height being more rather than less jealous. There was also a negative linear relationship for seductive behavior [F(1,225)=4.42, r=−.14, p=.037]. All remaining effects were not significant (F's≤2.21, p's≥.11).
Fig. 5. Linear and quadratic relationships between women's height and self-reported jealousy in response to a (A) physically attractiveness, (B) physically dominant, and (C) high social status rival.
Again, we examined whether BMI had predictive effects on jealousy. The BMIs were at normal levels: for men, mean=23.20 (S.D.=2.61), and for women, mean=20.96 (S.D.=2.42). There was no evidence that BMI had any effect (we calculated the correlations between BMI and the five jealousy scales, r's<.09, p's>.20), suggesting again that the impact of height on jealousy is independent of the impact that weight may also have on jealousy.
4. General discussion
In Study 1, the results showed that male height had only a linear relationship with jealousy, with taller men indicating less jealousy. Among women, a curvilinear relationship between height and jealousy was found indicating that average-height women reported the lowest level of jealousy. These findings are consistent with previous research suggesting that male height is associated with dominance, attractiveness, and potential reproductive success, which are expected to be associated with baseline jealousy. The different pattern of results for the female participants was also consistent with previous research suggesting that height may have a curvilinear relationship with attractiveness, health, and reproductive success among women (e.g., Nettle, 2002b, Silventoinen et al., 1999). The results of Study 1 showed no effect of male height on perceptions of their partner's sexual interest in others. This is intriguing, given the importance of paternity confidence for males. One might have expected height to be associated with this variable also—or especially—among males because men may be more concerned than women about their partner's sexual infidelity (e.g., Buss et al., 1992, Paul et al., 1993). How can we explain these results? One possibility is that women are more capable of, and more focused on, assessing their partner's intentions and desires. There is evidence that women tend to engage more in self-related information processing when confronted with potential interlopers (Buunk & Dijkstra, 2001). Indeed, the results showed that women's jealousy—but not men's jealousy—was positively correlated with perceptions of their partner's interest in others.
Using different measures focusing on rival characteristics, Study 2 corroborated and extended the findings of Study 1. Among men, only linear associations between height and jealousy were found: Taller men tended to be less jealous when confronted with socially influential, physically dominant, or physically attractive rivals. Among women, in addition to linear effects, curvilinear effects were found for three of the five rival characteristics. Overall, taller women tended to be less jealous than shorter women. Importantly, as predicted, quadratic effects indicated that, when confronted with physically attractive rivals, taller and shorter women were relatively more jealous than a linear trend would indicate. However, in response to physically dominant and high social status rivals, average-height women were relatively more jealous. Although this overall pattern of results was unexpected, we can offer a speculative explanation. Women may be least jealous of rivals who have features they have themselves and most jealous of rivals who have features they do not have themselves. As women of average height tend to be more fertile and healthy (Nettle, 2002b, Silventoinen et al., 1999), they would be less jealous of women with features signaling fertility and health such as physical attractiveness but more jealous of women possessing masculine features such as physical dominance and social status. This then suggests that the curvilinear effect observed in Study 1 may be restricted to physically attractive rivals. It is important to note that in Study 2, we found both linear and curvilinear effects of height on jealousy among women, and the linear effects consistently showed that taller women tend to be less jealous than short women. This may be due to the fact that, in general, taller women are more dominant and have greater fighting abilities than shorter women and may also be somewhat healthier (in terms of better nutrition, more physical activities, etc). Furthermore, it should be noted that women of average and above-average height did not differ substantially in their level of jealousy, suggesting that there might be a threshold for the effect of height on jealousy.
It is noteworthy that BMI had no relationship with jealousy. This may be because this index conflates muscularity and fatness. As more muscularity might be associated with less jealousy (especially among males), and as more fatness might be associated with more jealousy (especially among females in Western cultures in which thinness plays a role in female attractiveness), it remains an important task for future research to tease apart the effects of height, muscularity, and fatness. Nevertheless, the present findings suggest that height may have important psychological consequences, and they contribute to the emerging literature documenting physical features and psychological mechanisms that influence intrasexual competition and mate selection in humans.
This work was supported by a grant from the Royal Netherlands Academy of Arts and Sciences and by a research grant from the Spanish Ministry of Science and Education, Research Project: SEJ2006 14086/PSIC. We thank Shelli Dubbs, Martijn Wieling, and Kristina Potocnic for their assistance.
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