Science and the “Me Test”

Neuroscientist Simon LeVay has served on the faculties of Harvard Medical School and the Salk Institute for Biological Studies, and is well-known for a 1991 study in which he reported on a difference in brain structure between gay and straight men. His forthcoming book Gay, Straight, and the Reason Why: The Science of Sexual Orientation examines the evidence that suggests sexual orientation results primarily from an interaction between genes, sex hormones, and the cells of the developing body and brain. In this original post, LeVay explains how he initially reacts to new reported findings in this field.

I often lecture on the topic of sexual orientation. When I do, I sometimes mention research on finger lengths: according to several studies, the index fingers of lesbians are slightly shorter than those of straight women, when measured with respect to the other fingers. As I describe this research, I invariably see audience members examining their own fingers, as if doing so might reveal something unexpected about their sexuality. I hasten to make clear that the findings on finger lengths are based on statistical analysis of data from hundreds or thousands of subjects—they can’t be used to assess the sexual orientation of any particular individual.

Yet I myself use the “me test” as a gut reaction to any reported findings in the field. Not to figure out whether I’m really gay—I’ve been confident on that score since puberty—but as a quick, involuntary assessment of whether I believe that particular finding or not. As a teenager, for example, I read Freud’s theory of how close-binding mothers and distant or hostile fathers drive their sons toward homosexuality. This seemed to correspond to my own childhood experience: I was my mother’s favorite son, whereas I got on badly with my father. So I thought Freud must have been right. Now I believe that the direction of causation is the reverse of what Freud imagined: “pre-gay” boys tend to elicit adoration or protectiveness from their mothers, but rejection from their fathers.

Recent research has focused on gender-related traits in gay people. There have been over ninety such findings in the last couple of decades, covering personality, cognitive traits, behavior, anatomy (including the finger-length studies), physiology, and brain organization. Most have reported that gay men are shifted in the feminine direction in some traits, whereas lesbians and bisexual women are shifted in the masculine direction. As each study appears, I can’t help asking: is it true for me? Gay men (like straight women) have higher verbal fluency than straight men—check! Gay men have lower visuospatial abilities that straight men—check! Gay men have slightly shorter arms—check! I seem to be a pretty stereotypical gay man in many of these traits. Most researchers interpret these findings in terms of a biological predisposition to become gay or straight—a predisposition that results from an interaction between sex hormones and the developing brain and body. I certainly buy into that.

Other evidence has pointed toward a genetic influence on sexual orientation. For one thing, gay people tend to cluster in certain families, as if genes running in those families are predisposing their members toward homosexuality. The “me test” authenticated that one: I have a gay brother.

Another set of studies, however, points in a direction that doesn’t quite gel with my own experience. Canadian researchers have reported a birth-order effect: gay men, they say, are more likely to be later-born in families than are straight men, and are more likely to have at least one older brother. I do have an older brother, but I also have three younger brothers, so I’m fairly early in birth order. And what’s more, my older brother is gay too, even though he’s first-born, whereas my younger brothers are not.

So it was difficult for me to accept the birth-order studies. But they’ve now been confirmed often enough to persuade me that they’re correct, at least in a statistical sense. Interestingly, this birth-order effect holds up even if the children are brought up separately, so it doesn’t seem to be caused by the social experience of having older brothers. Rather, the Canadian researchers believe that women’s immune systems ‘remember’ how many sons they’ve had, and this immunological memory affects prenatal brain development in later sons, predisposing them to be gay.

It’s natural for people to take account of own life experiences when considering explanations for traits such as sexual orientation, but this kind of thought process can be fallible. Some women believe that childhood molestation caused them to be lesbian, for example. Yet such molestation is shockingly common, so many lesbians will have a history of childhood molestation, just on a chance basis. In fact, statistical studies don’t support a causal connection between molestation and homosexuality in women (or in men, for that matter).

In other words, it’s best to keep an open mind about what factors led you to your own sexual orientation, whether it be gay, straight, or bisexual. In my research, I drop the “me test” and stick to the science. Even science is fallible, of course, but it has a way of correcting itself over time, in part because the personal prejudices of individual scientists tend to cancel each other out.