Is sexual orientation similar to eye color, consisting of fairly discrete categories? Or is it more like height—that is, falling along a continuum? As a psychologist, I have explored that question in several venues, including the February/March 2006 issue of Scientific American Mind [“Do Gays Have a Choice?”]. Although common thinking holds that everyone is either “gay” or “straight,” my new survey of nearly 18,000 people who voluntarily answered an online quiz shows that these terms are highly misleading. Sexual orientation actually lies on a smooth continuum, and the way people state their orientation is often a poor predictor of their true sexual behaviors and fantasies. Someone can call himself “gay” but behave “straight,” and vice versa.

At the Society for the Scientific Study of Sexuality meeting in November, I will report that the same continuum of scores exists in the U.S. and in the average of scores from a dozen countries outside the U.S. I also find that fewer than 10 percent of subjects score as “pure” heterosexual or homosexual and that females place, on average, farther toward the gay end of the continuum than males do. My study suggests that characterizing sexual orientation properly requires two numbers: mean sexual orientation (where a given person lies on the continuum) and sexual orientation range (how much flexibility or “choice” the person has in expressing that orientation, which also forms a continuum).