Day By Day

Friday, April 29, 2005

Sex Differences -- The Biological Basis

Scientific American has a terrific article on recent research into sex differences.

Larry Summers may have backed off his call for consideration of the biological bases of male and female personalities and preferences but researchers at a number of institutions here and abroad are finding intriguing and important differences in mental structures and capacities between men and women.
Not so long ago neuroscientists believed that sex differences in the brain were limited mainly to those regions responsible for mating behavior.... A generation of neuroscientists came to maturity believing that "sex differences in the brain" referred primarily to mating behaviors, sex hormones and the hypothalamus.

That view, however, has now been knocked aside by a surge of findings that highlight the influence of sex on many areas of cognition and behavior, including memory, emotion, vision, hearing, the processing of faces and the brain's response to stress hormones. This progress has been accelerated in the past five to 10 years by the growing use of sophisticated noninvasive imaging techniques such as positron-emission tomography (PET) and functional magnetic resonance imaging (fMRI), which can peer into the brains of living subjects.

Researchers, including some at Harvard Medical School, have found significant differences in brain structure between men and women, even at the cellular level. Behavioral studies have also suggested that differences between men and women are innate over a wide spectrum of behavior rather than culturally determined. For instance, look at this work with vervet monkeys:

Through the years, many researchers have demonstrated that when selecting toys, young boys and girls part ways. Boys tend to gravitate toward balls or toy cars, whereas girls more typically reach for a doll. But no one could really say whether those preferences are dictated by culture or by innate brain biology.

To address this question, Melissa Hines of City University London and Gerianne M. Alexander of Texas A&M University turned to monkeys, one of our closest animal cousins. The researchers presented a group of vervet monkeys with a selection of toys, including rag dolls, trucks and some gender-neutral items such as picture books. They found that male monkeys spent more time playing with the "masculine" toys than their female counterparts did, and female monkeys spent more time interacting with the playthings typically preferred by girls....

Other research shows that infants as early as one day old show distinct patterns of behavior and attention according to their sex. Girl infants prefer to look at people's faces while boy infants are attracted to mechanical objects.

Read the whole article here.

This is a perfect illustration of why scientific research, the conclusions of which are constantly being revised, is an inadequate guide for the formulation of social policy. When the best scientific research showed that differences in brain structure and function between men and women were minimal, we concluded that gender was a social construct and shaped our public policies and institutions to reflect that belief. Then a few years later science turned on a dime and did an Emily Litella, collectively saying "never mind what we told you last year" we now believe that there are deep physical differences in brain structure and function between men and women that affect a wide range of behaviors.

Poor Larry Summers -- he got caught in the transition. The old beliefs had become institutionalized, well funded, and had developed articulate and lethal constituencies. When he raised the possibility that the new "devo-evo" approaches had some basis in truth, he got run over by an institutional imperative that, while still powerful, was increasingly divorced from scientific opinion.

I'm not saying that we should not listen to scientists. Just that their input must be balanced against a number of other considerations, including the moral implications of their findings.


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