Gender differences in self-esteem: A meta-analysis. - Kling, Kristen C.; Hyde, Janet Shibley; Showers, Carolin J.; Buswell, Brenda N. - 1999
Two analyses were conducted to examine gender differences in global self-esteem. In Analysis I, a computerized literature search yielded 216 effect sizes, representing the testing of 97,121 respondents. The overall effect size was 0.21, a small difference favoring males. A significant quadratic effect of age indicated that the largest effect emerged in late adolescence ( d = 0.33). In Analysis II, gender differences were examined using 3 large, nationally representative data sets from the National Center for Education Statistics (NCES). All of the NCES effect sizes, which collectively summarize the responses of approximately 48,000 young Americans, indicated higher male self-esteem ( ds ranged from 0.04 to 0.24). Taken together, the 2 analyses provide evidence that males score higher on standard measures of global self-esteem than females, but the difference is small. Potential reasons for the small yet consistent effect size are discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
In short not much of a difference between men and women, contrary to popular belief. And while I searched further I came across the "big five" again and remembered something I read somewhere else:
If the scientific evidence comes in that proves systematic, cross-cultural differences between men and women-- not "95% overlapping bell curves," but "the vast majority of men are more X than the vast majority of women"-- then that would destroy my feminism. If the 95% overlapping bell curves apply not to a few traits but to every trait from the Big Five to cooking ability, then that would also destroy my feminism.
Because that means that the social pressure is not the result of arbitrary stereotypes and fear of the different: it's an attempt to mold people so they will actually be similar to most people of their gender, which would aid their social and romantic life. Because that means the lack of stay-at-home dads and female CEOs is not the result of sexism, but of nature.
Having read that, I'd say it is definitely both. To what degree is debatable and in my opinion we should work on eliminating cultural factors (sexism). But this might also mean that even when we have achieved cultural equality there still might be some gaps in our favorite measurements of equality (wage gap, number of stay-at-home dads, number of female CEOs). So I came across cross-cultural studies of the big five that helped support the nature side of this argument. We start with an abstract for one because it is behind a paywall:
Gender differences in personality traits across cultures: Robust and surprising findings. - Costa Jr., Paul; Terracciano, Antonio; McCrae, Robert R. - Journal of Personality and Social Psychology, Vol 81(2), Aug 2001
Secondary analyses of Revised NEO Personality inventory data from 26 cultures (N =23,031) suggest that gender differences are small relative to individual variation within genders; differences are replicated across cultures for both college-age and adult samples, and differences are broadly consistent with gender stereotypes: Women reported themselves to be higher in Neuroticism, Agreeableness, Warmth, and Openness to Feelings, whereas men were higher in Assertiveness and Openness to Ideas. Contrary to predictions from evolutionary theory, the magnitude of gender differences varied across cultures. Contrary to predictions from the social role model, gender differences were most pronounced in European and American cultures in which traditional sex roles are minimized. Possible explanations for this surprising finding are discussed, including the attribution of masculine and feminine behaviors to roles rather than traits in traditional cultures.
The fascinating thing here is, the more egalitarian your society is, the more pronounced gender differences are. How come? The following study goes into more detail:
Why Can’t a Man Be More Like a Woman? Sex Differences in Big Five Personality Traits Across 55 Cultures - David P. Schmitt, Anu Realo, Martin Voracek, Jüri Allik - 2008
Previous research suggested that sex differences in personality traits are larger in prosperous, healthy, and egalitarian cultures in which women have more opportunities equal with those of men. In this article, the authors report cross-cultural findings in which this unintuitive result was replicated across samples from 55 nations (N 17,637). On responses to the Big Five Inventory, women reported higher levels of neuroticism, extraversion, agreeableness, and conscientiousness than did men across most nations. These findings converge with previous studies in which different Big Five measures and more limited samples of nations were used. Overall, higher levels of human development—including long and healthy life, equal access to knowledge and education, and economic wealth—were the main nation-level predictors of larger sex differences in personality. Changes in men’s personality traits appeared to be the primary cause of sex difference variation across cultures. It is proposed that heightened levels of sexual dimorphism result from personality traits of men and women being less constrained and more able to naturally diverge in developed nations. In less fortunate social and economic conditions, innate personality differences between men and women may be attenuated.
It goes further:
This study provides strong support for the claim that with greater human development and with greater opportunities for gender equality, the personalities of men and women do not become more similar (see also Costa et al., 2001; McCrae, 2002; McCrae et al., 2005). To the contrary, in more prosperous and egalitarian societies the personality profiles of men and women become decidedly less similar. Moreover, these changes appear to result from men’s cross-cultural personality variation. In more traditional and less developed cultures a man is, indeed, more like a woman, at least in terms of self-reported personality traits. [...]
Sex Roles Do Not Explain Why Sex Differences in Personality Traits Vary Across Cultures
An accumulating body of evidence, including the current data, provides reason to question social role explanations of gender and personality development (Baron-Cohen, 2003; Campbell, Shirley, & Candy, 2004; Geary, 1998; Lytton & Romney, 1991; Maccoby, 2000; Mealey, 2000; Spiro, 1996; Tiger & Shepher, 1975). In this study, a collection of eight different gender equality indicators provided a comprehensive set of measures that assess disparity between male and female roles in society. In every case, signifi-cant findings suggest that greater nation-level gender equality leads to psychological dissimilarity in men’s and women’s per-sonality traits. If differences in personality traits are controlled by the drastically different social roles that men and women play in the society then in cultures in which women earn considerably less than men, in which they have limited access to education, and in which only few of them become professionals, women’s person-ality profiles should be very different from men’s. In reality, these women’s personality profiles are more similar to those of men.
Evolutionary Theories May Explain Why Sex Differences in Personality Traits Vary Across Cultures
Evolutionary theories rooted in parental investment theory (Trivers, 1972) have predicted that sexual selection pressures have caused men to be more prone than women to take risks and seek social dominance, whereas women are thought to have been se-lected to be more nurturing and cautious (Buss, 1997; MacDonald, 1995). Thus, evolutionary theories can readily account for the existence of culturally pervasive differences between men and women. In principle, evolutionary theories can also explain the widening gap between the personalities of men and women by a version of the mismatch theory (specifically, the curvilinear hy-pothesis), according to which discrepancies between contemporary environmental conditions and those in which early humans evolved have begun to lessen as humans move from agricultural to modern societies (Schmitt, 2005a). [...] As societies rooted in agriculture and monotheism emerged, the personalities of men and women were relatively constrained and sex differences in personality may have been less likely to surface (see Pasternak et al., 1997). Finally, as modern societies have become more egalitarian (more similar to hunter-gatherer cultures; Marlowe, 2003; Yanca & Low, 2004), innate sex differences in personality traits may have become more likely to materialize. However, until there are larger studies that include a wider range of cultures—ideally including hunter-gatherer, horti-cultural, pastoral, agricultural, and developing nations—this cur-vilinear hypothesis must remain speculative.[...]
In summary, we have found that differences between men and women in their personality traits become more extreme with the increasing development of human society. Reported ISDP data indicate that human development—long and healthy life, access to education, and economic wealth—is a primary correlate of the gap between men and women in their personality traits. Most other correlates appear to be mediated by general level of development in health, education, and economy. In societies in which longevity is threatened by poor health, in which only a fraction of people have opportunities for a good education, and in which people suffer from economic hardship, the development of one’s inherent personality traits is more restrained. In these hold-down or mal-nourished conditions, there is a smaller variation around the mean level of personality traits across the ISDP, and it is more likely that any one individual is more like all other individuals. In traditional and less developed countries, therefore, an average man is more like an average woman, not in terms of his social roles or value preferences, but in his basic personality tendencies to feel, think, and act in a way more comparable with women.
Pretty fascinating. Wikipedia has a nice summary of the above study.
Cross-cultural research has shown some patterns of gender differences on responses to the NEO-PI-R and the Big Five Inventory. For example, women consistently report higher Neuroticism, Agreeableness, warmth (an extraversion facet) and openness to feelings, and men often report higher assertiveness (a facet of extraversion) and openness to ideas as assessed by the NEO-PI-R. A study of gender differences in 55 nations using the Big Five Inventory found that women tended to be somewhat higher than men in neuroticism, extraversion, agreeableness, and conscientiousness. The difference in neuroticism was the most prominent and consistent, with significant differences found in 49 of the 55 nations surveyed. Gender differences in personality traits are largest in prosperous, healthy, and egalitarian cultures in which women have more opportunities that are equal to those of men. Differences in the magnitude of sex differences between more or less developed world regions were due to differences between men not women in these respective regions. That is, men in highly developed world regions were less neurotic, extraverted, conscientious and agreeable compared to men in less developed world regions. Women, on the other hand tended not to differ in personality traits across regions. The authors of this studied speculated that resource poor environments (that is, countries with low levels of development) may inhibit the development of gender differences, whereas resource rich environments facilitate them. This may be because males require more resources than females in order to reach their full developmental potential. The authors argued that due to different evolutionary pressures, men may have evolved to be more risk taking and socially dominant, whereas women evolved to be more cautious and nurturant. Hunter-gatherer societies in which humans originally evolved may have been more egalitarian than later agriculturally oriented societies. Hence, the development of gender inequalities may have acted to constrain the development of gender differences in personality that originally evolved in hunter-gatherer societies. As modern societies have become more egalitarian again it may be that innate sex differences are no longer constrained and hence manifest more fully than in less developed cultures. Currently, this hypothesis remains untested, as gender differences in modern societies have not been compared with those in hunter-gatherer societies.