The Flaws in the Science of Sex Differences
Rebecca M. Jordan-Young
Harvard University Press:
394 pp., $35
Are men and women really two planets apart? In "Brain Storm," Rebecca M. Jordan-Young, a Barnard College professor of women's studies, sets out to debunk the proliferating "brain-organization" studies that attempt to explain in purely biological terms (since XX and XY seem not to be enough) why males and females differ in one way or another. Or, in some cases, fail to differ.
Issues of gender understandably provoke a lot of red-faced uproar in all sorts of warring quarters. Neuroscientist Simon LeVay's 1991 report in Science locating male homosexuality in an area of the hypothalamus and Lawrence H. Summers' suggestion, while he was still president of Harvard, that the unequal number of tenured male and female scientists indicates "a difference in aptitude" are signal examples.
Jordan-Young, a sociomedical scientist (it's a portmanteau field, embracing psychology, sociology, anthropology and health policy), was particularly troubled by LeVay's findings, which she found "interesting but also puzzling. How could gayness take a single identifiable form in the brain when it takes such varied forms in people's lives?" The book resulting from her puzzlement is a refreshing and sensible look at the conduct of an area of science that is perhaps not as empirical as it should be.
Part of the reason is that brain-organization research — when humans are the subjects — must confine itself to what Jordan-Young calls "quasi-experiments." That is (to simplify a great deal), while you can pump hormones into a rat and watch what happens, you can do no such thing with a human being. When it comes to the effects of prenatal hormone exposure — a focus of brain-organization studies on sex-typed predilections, and also Jordan-Young's focus — researchers must collect data from the unmolested living.
Jordan-Young spent 13 years on a "synthetic analysis" of hundreds of studies dating from 1967, when they were first applied to humans, to 2000, when the glut of data "made it no longer possible to examine every published study in depth," comparing methods as well as results and interviewing nearly two dozen of the field's leaders. She was interested "in how scientists resolved the problem of measuring something as complex as sexuality or gender in such a way that these ... could be associated with brain structure or hormone exposures." It's worth a hard look: Once that association is reified, she points out, the consequences are profound — affecting, among other things, not just how we view gay people (or how they view themselves), but how we raise and educate our children and how we assign or adopt social and professional roles.
What Jordan-Young's analysis uncovered is by turns fascinating and appalling. Investigators' assumptions morph; definitions slip and slide. For instance, the modern notion (currently slipping) that the male sexual appetite is greater than the female's "is the exact reverse of the idea in Renaissance Europe." Definitions aside ("one scientist's heterosexuals are another scientist's homosexuals"), when these studies are juxtaposed, what emerges is an absence of context — a comparing of apples, Tuesday and Belgium. Left-handedness is more common in men than in women; lesbians tend to be left-handed; so do gay males. One study of "toy preferences" in vervet monkeys was ambiguous, since the boy vervets seemed most interested in the plush dog (a toy deemed "neutral") and the girl vervets paid relatively little attention to the doll. The girl vervets did prefer playing with the toy cooking pot, but exactly what they did with it was not reported. Children born with ambiguous genitalia because of prenatal hormone imbalance indeed perform differently from their "normal" peers in behavioral studies, but those children have undergone (often horrifying) medical interventions and have also been reared differently.
Jordan-Young's point "is not that hormone effects are not 'real.'... [T]hey do figure into development, including neural development, in a variety of important ways. Nor is the point that males and females aren't 'really' different.... The problem is the way that brain organization theory ... attributes an unrealistic specificity and permanence to early hormone effects, as well as a demonstrably false inevitability and uniformity to sex differences.... Even in rats, early hormone exposures do not create a solid foundation on which behavior must forever stand."
Good news for rats — and the news is good for us too. What happens to us prenatally might be unlucky, but "[t]he ultimate phenotype isn't apparent at birth or even ... in childhood or adolescence. In fact, brain development is not completely 'finished' at any point prior to death."
Isn't that nice to hear? This book is not only a tonic, it's also full of scientific insights presented in plain, intelligent prose — an absorbing read, if you've ever wondered what was going on in the secret parts of your attic.
Lippincott is a freelance editor specializing in science.