Why are men underrepresented in teaching, child care, and related fields and women underrepresented in engineering, physics, and related fields? I used to know the answer, but that was before I spent several decades reviewing almost everything written about this question. Like most enduring questions, the responses have grown more contentious and even less is "settled" now that we have mountains of research designed to answer them. At some point, my own answer changed from what I believed to be the simple truth to a convoluted statement complete with qualifiers, hedge terms, and caveats. I guess this shift in my own thinking represents progress, but it doesn't feel or look that way.
I am a feminist, a product of the 60s, who believed that group differences in intelligence or most any other trait are mostly traceable to the lifetime of experiences that mold us into the people we are and will be. Of course, I never doubted the basic premises of evolution, but the lessons that I learned from evolution favor the idea that the brain and behavior are adaptable. Hunter-gatherers never solved calculus problems or traveled to the moon, so I find little in our ancient past to explain these modern-day achievements.
There is also the disturbing fact that evolutionary theories can easily explain almost any outcome, so I never found them to be a useful framework for understanding behavior. Even when I knew the simple truth about sex differences in cognitive abilities, I never doubted that heritability plays a role in cognitive development, but like many others, I believed that once the potential to develop an ability exceeded some threshold value, heritability was of little importance. Now I am less sure about any single answer, and nothing is simple any more.
The literature on sex differences in cognitive abilities is filled with inconsistent findings, contradictory theories, and emotional claims that are unsupported by the research. Yet, despite all of the noise in the data, clear and consistent messages can be heard. There are real, and in some cases sizable, sex differences with respect to some cognitive abilities.
Socialization practices are undoubtedly important, but there is also good evidence that biological sex differences play a role in establishing and maintaining cognitive sex differences, a conclusion that I wasn't prepared to make when I began reviewing the relevant literature. I could not ignore or explain away repeated findings about (small) variations over the menstrual cycle, the effects of exogenously administered sex hormones on cognition, a variety of anomalies that allow us to separate prenatal hormone effects on later development, failed attempts to alter the sex roles of a biological male after an accident that destroyed his penis, differences in preferred modes of thought, international data on the achievement of females and males, to name just a few types of evidence that demand the conclusion that there is some biological basis for sex-typed cognitive development.
My thinking about this controversial topic has changed. I have come to understand that nature needs nurture and the dichotomization of these two influences on development is the wrong way to conceptualize their mutual influences on each other. Our brain structures and functions reflect and direct our life experiences, which create feed back loops that alter the hormones we secrete and how we select environments. Learning is a biological and environmental phenomenon.
And so, what had been a simple truth morphed into a complicated answer for the deceptively simple question about why there are sex differences in cognitive abilities. There is nothing in my new understanding that justifies discrimination or predicts the continuation of the status quo. There is plenty of room for motivation, self-regulation, and persistence to make the question about the underrepresentation of women and men in different academic areas moot in coming years.
Like all complex questions, the question about why men and women achieve in different academic areas depends on a laundry list of influences that do not fall neatly into categories labeled biology or environment. It is time to give up this tired way of thinking about nature and nurture as two independent variables and their interaction and recognize how they exert mutual influences on each other. No single number can capture the extent to which one type of variable is important because they do not operate independently. Nature and nurture do not just interact; they fundamentally change each other. The answer that I give today is far more complicated than the simple truth that I used to believe, but we have no reason to expect that complex phenomena like cognitive development have simple answers.