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.
