Whenever I post on evolutionary psychology, lurkers come out of the woodwork, enraged that I’ve criticized their own discipline and vociferously defending the crappy papers that I sometimes highlight. Recently one (or more) of the lurkers asked me to provide an example of an evo-psycho paper that I considered good. Well, that made me think a bit. Many of the papers are tolerable rather than outright lousy, but in my opinion good ones are rare. But I’ve just read one that I’d put in the “pretty good” category. Some might not consider the subject to be evolutionary psychology, but I think it is, for it’s about whether behavioral differences between males and females have a genetic basis. If they do, then one can begin to uncover their evolutionary roots. If they don’t, then we need not engage in adaptive storytelling about why males are aggressive and females are nurturing.
It’s a paper on “gender construction” by two doctors, William Reiner and John Gearhart, and it appeared in 2004 in the New England Journal of Medicine. The jaw-breaking title is “Discordant sexual identity in some genetic males with cloacal exstrophy assigned to female sex at birth”. (The pdf appears to be free.) I found the reference to this paper in the “gender” chapter of Steve Pinker’s The Blank Slate.
The topic is one that used to exercise academics, especially feminist ones: is gender-specific behavior and identity specified at birth by biological factors like genes and hormones, or is gender “constructed” by the way a child is raised? I well remember feminists saying that if you could somehow raise a male child as a girl, or vice versa, they would show behaviors and personalities opposite to that of their “normal gender.” Or, if you could raise children in a “gender neutral” environment, then males and females would grow up not differing in gender-specific behaviors (i.e., girls would play with trucks, boys with dolls, and, when adult, males would not be more aggressive nor females more “nurturing.”) As the authors put it very dryly in their paper,
The concept of neonatal sexual neutrality subsequently developed, emphasizing postnatal, nonhormonal influences.
Now perhaps most of my readers already reject the concept of “gender neutrality” at birth, a neutrality suborned by rearing practices. We know that injecting testosterone into females, for example, increases some “male-typical” behaviors (like aggression) and physical traits. It’s clear that hormones have an influence on behavior, and in precisely the way predicted by which sex has the highest testosterone/estrogen ratio and vice versa. But what about at birth? Are newborns already wired up to show sex-specific behavior?
Reiner and Gearhart tested this by doing psychological studies on children born with cloacal exstrophy, a severe condition in which (in males) the genitals are malformed (but not the testes), and there are defects of the bowels and bladder. It used to be fatal, but now can often be fixed by surgical intervention. (Often, however, medical problems remain, like the need for a colostomy or the later appearance of sciolosis). If you have a strong stomach, click on this link to see what a newborn with the syndrome looks like (go halfway down the page).
Reiner and Gearhart’s idea was this: if gender is “constructed” by socialization at birth, newborns who are raised as members of the opposite sex from birth should show behaviors characteristic of their “socialized” sex rather than their biological sex. Cloacal exstrophy gave them a chance to do this, because males born with the syndrome sometimes have their penises and testes removed, a vulva constructed instead, and are raised as girls. If the “socialization” hypothesis is correct, these males should show female-typical behaviors when older; if the biological hypothesis is correct, they should lean towards male behaviors.
The authors had a sample of fourteen newborn males with cloacal exstrophy whose parents agreed to participate in the study. The babies were surgically constructed to have female genitalia, and parents agreed to raise the boys as girls, never telling the children of their biological gender. (Two other males with the syndrome were raised as males even though they had the surgery.) Several of the parents were raising “normal” girls at the same time.
At ages ranging from 5 to 16, the female-raised males were given psychological tests that explored their interests in toys, dolls, and clothes, the time spent playing various games, athleticism, aggressive behavior, career and sexual interests, sex of friends, etc. They were also asked to declare their gender. The parents were also given questionnaires on their child’s behavior and relationships with other children.
The upshot: all 16 subjects, including those with female genitals raised as males, “revealed moderate-to-marked male-typical behaviors” compared to the scores of children raised according to their biological sex at birth. (The paper reports the scores for each child on a number of scales.) As for the parents, here’s what the authors report:
The parents of all 14 subjects assigned to female sex stated that they had reared their child as a female. Twelve of these subjects have sisters: parents described equivalent child-rearing approaches and attitudes toward the subjects and their sisters. However, parents described a moderate-to-pronounced unfolding of male-typical behaviors and attitudes over time in these subjects — but not in their sisters. Parents reported that the subjects typically resisted attempts to encourage play with female-typical toys or with female playmates or to behave as parents thought typical girls might behave. These 14 subjects expressed difficulties fitting in with girls. All but one played primarily or exclusively with male-typical toys. Only one played with dolls; the others did so almost never or never. Only one ever played house. Each of the three exceptions represents a different subject. Parents noted substantial difficulty attempting to dress the subjects — but not their sisters — in clearly feminine attire after about four years of age.
And, tellingly, of the 14 subjects, four of them declared themselves as “males” even though they had female-type genitalia, had been raised as girls, and had never been told of their birth sex. Four more were actually told of their birth sex by parents who abrogated the agreement, and all four of them declared themselves males. At the last follow-up, two more of the children were “unclear” about their sex, and another one refused to discuss it. (I believe, but am not sure, that the initial assessment of self-declared sex, and the children’s psychological tests, were performed before those four had been told that they were born male.)
At the end of the study, all eight of the male-declarers used male names and male restrooms, and all eight wanted surgical reconstruction of a penis. The other six still living as females all reported difficulty fitting in with female peers, a result not seen at all in cases of genetic females with cloacal exstrophy).
The conclusion: babies are born with brains already wired up in a gender-specific way. The authors theorize that this is due to pre-natal hormonal influences on the fetal brain that affect subsequent behavior. And although the study has weaknesses (see below), I agree with this conclusion. The results show that, to a large extent, the roots of gender-specific behavior are biologically rather than socially based, and are present at birth. This jibes with the experience of many of my friends who are parents, who report that despite their efforts to raise kids in gender-neutral ways, male toddlers go for trucks and females for dolls. The fact that rearing genetic males as females does not much affect their behavior indicates that socialization, at least via parenthood, plays at best a small role in the development of behavior.
Now the study is not perfect, and I’m sure readers (especially the evolutionary psychologists) will tell me that this study is just as flawed as those I’ve criticized previously. There is no explicit comparison with the psychology of genetic females with cloacal exstrophy reared as females (though the authors do cite their impressions), the psychological scores of the children were not compared statistically to those of “normal” males and females of the same age (though one can certainly do this given the data given by the authors), and four of the subjects were told that they were born as males (at ages 5, 7, 7, and 18 respectively). But the psychological profiles of the children were taken before any were told of their birth sex (and most were not), as well as the self-declaration by four subjects that they were “males”, is pretty telling.
This is not my field, and there may have been followup work confirming or refuting these findings since they were published 7 years ago. (If you know of any, do post below; Pinker quotes some other studies that support these results.) But if the results hold up, they show pretty clearly that gender-specific behavior has strong biological roots, and may not be much changed by how a child is raised. In other words, even if you give your male toddlers dolls and your girls toy soldiers, they’re not going to become gender-neutral.
Why is this study better than many run-of-the-mill evolutionary psychology papers? First, because the authors took advantage of developmental accidents to do a study that normally would be either prohibited or impossible: psychologists rearing babies in either a totally gender-neutral environment or in which they do not know their sex. Many evo-psycho hypotheses simply can’t be tested properly because they require manipulations of adults or infants that are considered unethical.
Second, the study comprises a simple test of a simple hypothesis, and does not involve telling tortuous adaptive “stories” to rationalize the results.
Finally, the results are pretty clean cut: amazing, in fact. Given the limitations of the study—the small sample size, the parents who abrogated their promises, and so on—the results still stand out clearly. Whatever biological gender a child has at birth will condition its later behavior in a strong way.
Reiner, W. G. and J. P. Gearhart. 2004. Discordant sexual identity in some genetic males with cloacal exstrophy assigned to female sex at birth. New Engl. J. Med. 350:333-341.