This chapter was divided into five parts. Part 1 documented growing evidence of numerous universal ASDCBs (average sex differences in cognition and behavior). In particular, work by colleagues and myself led us to tentatively identify 65 such traits (Ellis, 2011a, 2011b; Ellis et al., 2008).
In Part 2, studies pertaining to three questions about ASDCBs were explored. First, have people’s attitudes toward sex equality changed, and if so, in what direction? The answer is that these attitudes have changed. At least in the United States, acceptance of women being educated and allowed to work in jobs alongside men has grown considerably since the 1970s (Thornton & Young-DeMarco, 2001).
Second, have sex stereotypes changed, and if so, how? The answer appears to be that sex stereotypes have changed very little during the past few decades at least in the United States. Specifically, people’s beliefs about how males and females differ in terms of basic interests, personality, and behaviors appear to have remained virtually the same in the 1990s as they were in the 1970s (Lueptow, 2005; Lueptow et al., 2001).
Third, have there been changes in men’s and women’s self-perceptions regarding their masculinity/femininity? In other words, do the sexes today think of themselves as just masculine, feminine, or somewhere in between, as was true in their parent’s generation? The evidence suggests that the answer is that little has changed, with the possible exception of contemporary women having somewhat more feminine interests than those sampled in the 1970s (Twenge, 1997).
(p. 511) The issue addressed in Part 3 had to do with making cross-cultural comparisons regarding sex differences in personality. Surprisingly, the evidence suggests that greater sex differences exist in most Western industrialized societies than in most non-Western developing societies (Costa et al., 2001; Hopcroft & Bradley, 2007; Hopcroft & McLaughlin 2012; Schmitt et al., 2016). This finding seems counterintuitive because considerably more effort has been made in most Western societies to encourage sex equality than has been made in most non-Western societies.
Part 4 described the three theories that have been proposed for explaining ASDCBs. The oldest one to be proposed is social role theory (Eagly & Wood, 1999). This theory asserts that males and females would be virtually identical in how they think and behave if it were not for sex differences in sociocultural training and expectations (Eagly et al., 2000). Surveys among sociologists indicate that it remains the most popular theory among social scientists (Horowitz et al., 2014; Sanderson & Ellis, 1992).
Beginning in approximately the 1970s, Darwin’s theory of evolution began to be specifically applied to the study of human ASDCBs (Hrdy, 1981; Wilson & Daly, 1978). Since then, numerous others have advocated an evolutionary approach to the study of ASDCBs (Archer, 1996; Geary, 2010; Hopcroft, 2016; Mealey, 2000). An evolutionary perspective explains why males and females think and behave differently based on how the sexes differ in their contributions to the reproductive process. In other words, the rate at which humans leave descendants (and therefore their genes) in future generations depends heavily on males and females thinking and behaving differently. Thus, whether operating through differential learning or some biological process, the most reproductively successful males will exhibit thought and behavior patterns than on average differ from those of the most reproductively successful females.
I have proposed a version of evolutionary theory that specifically incorporates brain and hormonal concepts (Ellis, 2006, 2011a, 2011b). This theory, called evolutionary neuroandrogenic (ENA) theory, is specifically designed to explain average sex differences in cognition and behavior. According to this theory, all mammals (including humans) are essentially females. However, a special chromosome has evolved that carries genes for making roughly half of these would-be females into males instead. In essence, these genes operate by causing the would-be female ovaries to develop into testes, special organs for producing large quantities of a masculinizing hormone called testosterone (along with other male hormones, called androgens). Androgens affect thought and behavior by infiltrating the brain both prenatally and following puberty. As a result of greater androgen exposure, males on average end up thinking and behaving in ways that serve their reproductive interests, whereas low androgen exposure in females causes them to think and behave in ways that generally contribute to their reproductive interests.
Finally, Part 5 addresses the question of how well the three theories described in Part 4 can shed light on the evidence summarized in Parts 1–3. Social role theory has difficulty explaining why there are numerous universal ASDCBs as discussed in Part 1. It also predicts that ASDCBs would weaken as societies become more sex egalitarian, which Parts 2 and 3 indicate have not happened.
(p. 512) Because evolutionary theory assumes that most ASDCBs have been naturally (or sexually) selected, it is able to account for why large numbers of ASDCBs exist, as indicated in Part 1. Furthermore, the evidence cited in Part 2 that people’s stereotypes about sex differences and their self-concepts in terms of masculinity/femininity have changed very little in recent decades is also understandable in an evolutionary context. ENA theory, as an extended version of evolutionary theory, goes on to hypothesize that androgenic effects on the brain explain how ASDCBs have evolved. It remains to be seen if most ASDCBs are the result of neuroandrogenic factors, but at least one recent test of this hypothesis regarding sex differences in mate preferences provided moderate support (Ellis & Ratnasingam, 2015).
The evidence that sex differences in personality traits appear to be more pronounced in Western industrial societies than in most non-Western developing societies (Part 4) presents a conundrum for all three theories of ASDCBs. It is especially devastating to social role theory, which is based on the assumption that gender differences would be least prevalent in cultures that foster the greatest degree of “gender equality” (Schmitt et al., 2016). The fact that most sociologists subscribe to this theory more than any other (Horowitz et al., 2014; Sanderson & Ellis, 1992) suggests that a sea change is in the offering for how social scientists think about cognitive and behavioral sex differences.
There seems to be only a few ways to explain why the most sex egalitarian societies have the greatest degree of sex differences in terms of personality traits. One possibility is that more of the genes responsible for sex differences in cognitive and behavioral traits have accumulated in Western populations than in non-Western populations. If so, one would be likely to find that sex differences in physical traits would also be more prevalent in Western populations, a possibility for which I could find no evidence.
Another possibility is that by being more lenient in allowing its citizens to express themselves in sex-related terms, males in Western cultures may end up thinking and behaving in more male-typical ways, and females in more female-typical ways, than is typical of non-Western cultures. If this second line of reasoning is true, it would turn traditional sex-role theorizing on its head. In other words, social scientists who argue that one should not stereotype or try to influence people’s behavior according to “conventional sex roles” because it contributes to sex inequality are mistaken. To the contrary, the effects of culturally prescribed sex roles would actually be inhibiting the expression of sex differences in thought and behavior. Thus, the more equitably males and females are treated by their sociocultural surroundings, the more different men and women will become.
In closing, I offer a proposal for social scientists to consider and test during the ensuing years. It is partly based on evidence that arranged marriages, particularly among close relatives (usually first cousins), are widespread both historically and even today in most developing countries (Desai & Andrist, 2010; Jurdi & Saxena, 2003). Contemporary developed countries appear to be among the only cultures in which arranged consanguineal marriages are rare (Hatfield, Rapson, & Martel, 2007).
I propose that one of the effects of freely marrying individuals from large pools of nonrelatives is that this cultural practice allows the expression of genes for traits to be (p. 513) maximized. This includes genes responsible for sexually dimorphic cognitive and behavioral traits. If so, it is in societies in which out-marrying is most common—that is, primarily Western industrial countries—that one will find the expression of genes for masculine traits in males and feminine traits in females to be the greatest.
Overall, it is clear that research is still needed to identify ASDCBs and to understand the factors responsible for them and for why they appear to be more pronounced in some cultures than in others. Nevertheless, the accumulation of ASDCB research so far is yielding tantalizing surprises that could fundamentally challenge some of sociology’s more cherished assumptions.