Researchers Find Difference in Gays
Mar. 03, 1998
WASHINGTON (AP) _ The inner ear of lesbian women works more like that of men, according to researchers who say the finding is the first strong evidence of physiological differences between gay and straight women.
Experts say the discovery, published today in the Proceedings of the National Academy of Sciences, adds new support to the theory that sexual orientation in women may be determined by biology and not choice.
Currently there is a controversy over the origin of homosexuality. Some groups believe it to be a matter of choice and have spent considerable effort attempting to find a ``cure'' for being gay. Many in the gay community, however, insist that being homosexual is a matter of biology.
Researchers at the University of Texas, Austin, said their studies show the inner ears of female homosexuals has undergone ``masculinization,'' probably from hormone exposure before birth.
``Their auditory centers have been masculinized and the presumption is that so have the sites in the brain that direct sexual preference,'' said Dennis McFadden, lead author of the study. He said it has yet to proven, however, that there is a specific site in the brain that directs women to be lesbians.
Dr. Michael Bailey of Northwestern University, said the research is ``compelling'' and may be ``consistent with the biological origin of lesbianism.''
He added: ``The most likely interpretation is that this represents some kind of effect of early hormones on the developing fetus.''
Bailey cautioned, however, that the research will not be accepted as valid until others replicate the experiment.
Sandra Witelson, an expert on brain anatomy and sexual orientation at McMaster University in Ontario, Canada, said the study results support the theory that lesbianism may be ``related to early factors in brain development.''
Researchers earlier found that two parts of the male brain are different in gay men. Other studies have found that some genes differ between gay and straight men.
McFadden, a professor of experimental psychology, said the inner ear difference between homosexual and heterosexual women was detected using a test that measures the function of the cochlea, a key sound amplifier in the inner ear.
The cochlea amplifier in women is more sensitive than that of men, giving women an increased ability to detect very soft sounds in a very quiet room.
The difference, said McFadden, can be measured by a test called clicked-evoked otoacoustic emission, or CEOAE. McFadden said that this test measures a very slight sound that the cochlea makes when responding to a soft clicking sound in a quiet room.
``When you present a click to a normal inner ear, it gives back a sound that is like an echo,'' said McFadden. ``It is very, very weak and it is very short, only a few tens of milliseconds.''
Females, with their more sensitive cochlea, respond more powerfully to this test than do men, said McFadden. This is true even among infants, the study said.
To test for CEOAE differences between the sexes, the researchers recruited more than 200 adults divided into four groups: homosexual women and men, and heterosexual women and men. Some from each of the four groups were later identified as bisexual. The sexual orientation of the subjects was self-identified or determined by questionnaire.
McFadden said that each subject was given the CEOAE test and the tests were then evaluated with the researchers being unaware of the subjects' sexual orientation.
The results, he said, showed that homosexual women had click-responses that were significantly weaker than those of straight women. The signal was weaker still for all males, both gay and straight. Bisexual men and women were in the middle, although McFadden said there was not enough of those in the study to draw firm conclusions.
What is clear, he said, is that there is a dramatic difference in the development of the hearing systems of lesbians and of straight women, and that it is known that development of the inner ear is affected before birth by androgens, a male hormone.
Androgens, said McFadden, may also ``alter the brain centers that produce sexual orientation,'' but he said researchers have yet to find a brain structure that determines sexual orientation in women.