Mar. 3, 1998 WASHINGTON, D.C. March 3 -- Scientists have found the first physiological difference between heterosexual and homosexual women. Echo-like sounds made by the inner ears of homosexual and bisexual women are weaker than the same sounds made by heterosexual women, according to a new report.
"The finding suggests that the inner ears and some unknown brain structures responsible for sexual preference are masculinized in homosexual and bisexual women because men also exhibit weaker echo-like sounds in their inner ears," says Dennis McFadden of the University of Texas, lead author of the study. "The study also indicates that the inner ear may be a valuable non-invasive window into events that occur during brain development and sexual differentiation."
McFadden's study, funded by the National Institute on Deafness and Other Communication Disorders, is published in the March 3 issue of the Proceedings of the National Academy of Sciences.
"The report is an elegant study of subtle auditory phenomena in gay and heterosexual people," says Sandra Witelson, an expert in the relationship of brain anatomy and function to sexual orientation at McMaster University in Ontario. "The results support the theory that differences in the central nervous system exist between homosexual and heterosexual individuals and that the differences are possibly related to early factors in brain development."
In the past, research that examined neurobiological differences between gays and heterosexuals has focused more on males than females. To date, findings implicate differences in brain structures, hand preference and fingerprint patterns. "Our finding reveals the first physiological characteristic related to homosexuality in females," says McFadden.
In the new study, the researchers examined a type of sound made by the inner ear known as a click-evoked otoacoustic emission. The echo-like sound is made by the inner ear in response to a weak click sound, such as the tap of a pencil on a desk. "The emissions are generally stronger in females than in males, throughout life," says McFadden. "But we found that the emissions of 61 homosexual and bisexual women were weaker than those of 57 heterosexual women, or in the male direction." The researchers found no differences in strength between homosexual and bisexual women or between gay and heterosexual men.
People with strong click-evoked otoacoustic emissions generally are better at hearing weak sounds. The researchers plan to determine if gay women have weaker hearing sensitivity in comparison to heterosexual women. They also plan to see if additional auditory differences exist between homosexuals and heterosexuals.
McFadden is a member of the Society for Neuroscience, an organization of more than 27,000 basic scientists and clinicians who study the brain and nervous system.
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