Excerpted from Why Is the Penis Shaped Like That? … And Other Reflections on Being Human, by Jesse Bering, by arrangement with Scientific American/Farrar, Straus and Giroux, LLC (North America), Transworld Ltd (UK), Jorge Zahara Editora Ltda (Brazil). Copyright © 2012 by Jesse Bering.
We all know the stereotypes: an unusually light, delicate, effeminate air in a little boy's step, an interest in dolls, makeup, princesses and dresses, and a strong distaste for rough play with other boys. In little girls, there is the outwardly boyish stance, perhaps a penchant for tools, a square-jawed readiness for physical tussles with boys, and an aversion to all the perfumed, delicate trappings of femininity.
These behavioral patterns are feared, loathed and often spoken of directly as harbingers of adult homosexuality. It is only relatively recently, however, that developmental scientists have conducted controlled studies to identify the earliest and most reliable signs of adult homosexuality. In looking carefully at the childhoods of gay adults, researchers are finding an intriguing set of behavioral indicators that homosexuals seem to have in common. Curiously enough, the age-old homophobic fears of many parents reflect some genuine predictive currency.
J. Michael Bailey and Kenneth J. Zucker, both psychologists, published a seminal paper on childhood markers of homosexuality in 1995. Bailey and Zucker examined sex-typed behavior—that long, now scientifically canonical list of innate sex differences in the behaviors of young males versus young females. In innumerable studies, scientists have documented that these sex differences are largely impervious to learning. They are also found in every culture examined. Of course, there are exceptions to the rule; it is only when comparing the aggregate data that sex differences leap into the stratosphere of statistical significance.
The most salient differences are in the domain of play. Boys engage in what developmental psychologists refer to as “rough-and-tumble play.” Girls prefer the company of dolls to a knee in the ribs. Toy interests are another key sex difference, with boys gravitating toward toy machine guns and monster trucks and girls orienting toward baby dolls and hyperfeminized figurines. Young children of both sexes enjoy pretend play, but the roles within the fantasy context are gender-segregated by age two. Girls enact the role of, say, cooing mothers, ballerinas or fairy princesses, and boys prefer to be soldiers and superheroes. Not surprisingly, therefore, boys naturally select other boys for playmates, and girls would much rather play with other girls.
So on the basis of some earlier, shakier research, along with a good dose of common sense, Bailey and Zucker hypothesized that homosexuals would show an inverted pattern of sex-typed childhood behaviors—little boys preferring girls as playmates and becoming infatuated with their mother's makeup kit; little girls strangely enamored of field hockey or professional wrestling—that sort of thing. Empirically, the authors explain, there are two ways to investigate this hypothesis, with either a prospective or retrospective study. Using the prospective method, young children displaying sex-atypical patterns are followed into adolescence and early adulthood so that their sexual orientation can be assessed at maturity.
This method is not terribly practical for several reasons. Given that a small proportion of the population is homosexual, prospective studies require a large number of children. This approach also takes a long time, around 16 years. Finally, not a lot of parents are likely to volunteer their children. Right or wrong, this is a sensitive topic, and usually it is only children who present significant sex-atypical behaviors who are brought into clinics and whose cases are made available to researchers.