Startling Study Says People May Be Born Gay
Researchers say key is in brain's innate response to sudden noise
MONDAY, Oct. 6 , 2003 (HealthDayNews) -- The origins of sexual orientation may be evident in the blink of an eye.
In what is the latest study to show an apparent link between a non-learned trait and sexual orientation, British researchers have discovered the way peoples' eyes respond to sudden loud noises may signal differences between heterosexual and homosexual men and women that were developed before birth.
The authors, whose study appears in the October issue of Behavioral Neuroscience, say about 4 percent of men and 3 percent of women are gay. Scientists have long sought to determine whether sexuality is learned or biological.
"We have several decades of research which suggests rather strongly that human sexual orientation is to some degree biologically determined," says study author Qazi Rahman, a lecturer in the School of Psychology at the University of East London. "The problem with those types of studies is that we can't disentangle the effects of learning."
The question then became, "What kind of task could be used that is not influenced by learning or socialization?" The answer came in human startle responses, which are involuntary and instinctual.
Specifically, Rahman and his colleagues decided to use pre-pulse inhibition (PPI). When humans hear a sudden noise, they respond by blinking. If that loud noise is preceded by a quieter noise (the pre-pulse), the response to the second, loud noise is weaker. In other words, it is inhibited.
The researchers compared responses to a loud noise both alone and after a quieter noise to see what the degree of inhibition was. Participants were 59 gay and straight men and women.
In the heterosexual women, the PPI averaged 13 percent and, in heterosexual men, 40 percent.
Lesbians, however, had a PPI of 33 percent, closer to the straight-man end of the spectrum, while gay men averaged 32 percent, slightly lower than that of straight men but not statistically significant.
The findings are consistent with other studies, which have found that certain traits in lesbians are highly "masculinized," while the same traits in gay men are almost the same as in straight men.
While it's difficult to make generalizations about gay behavior on the basis of these findings (for example, "all gay male thinking is like that of women"), it is possible to build a case for the origins of sexuality, the authors say.
"On the basis of these results and in conjunction with the bulk of the literature in the last three decades or so, the evidence points to some prenatal factor or factors [in determining sexual preference]," Rahman says.
The findings could have implications for a number of social issues.
"Actual sexual orientation and sex-related research is now being accepted as a legitimate national investment in terms of research," Rahman says. "We have problems with STDs [sexually transmitted diseases]. Understanding sexual behavior is clearly important to that."
The findings may also help illuminate sex differences in mental health issues. "Although homosexuality per se is not related to psychiatric problems, on those occasions that gays and lesbians do present with psychiatric problems, they often show disorders that are typical of the opposite sex," Rahman says. Gay men, for example, may be more likely to suffer depression, anxiety and eating disorders than their straight counterparts, while lesbians may be more vulnerable to substance abuse than heterosexual women.
"Maybe having an understanding of brain basis of sexual orientation in healthy individuals may give us some clues in what is going wrong in the brain circuitry underlying certain psychiatric problems," Rahman says. "In the future, we may be able to tailor treatments more specifically."
It's important not to draw too many generalizations. "It's not that the gay brain is like the heterosexual brain of the opposite sex. It seems to be a mosaic of male and female typical traits," Rahman says. "Because we're looking at humans, thing are always more complicated that you would expect."