Michael Sylvester was challenged about his remark of "talk" of an association between the
Post by michael sylvesterIt either came from LeVay or check out a Brain/Mind video
I thought this was interesting, so I looked into it. There is no published work, as far as I can
find, on the corpus callosum and sexual orientation. However, Allen and Gorski (1992) did
report that the anterior commissure was larger in homosexual than in heterosexual men.
The anterior commissure is a bundle of nerve fibers which, like the corpus callosum,
connects the two hemispheres of the brain. However, it's smaller than the corpus callosum
and deeper within the brain. Its function is largely unknown. So the claim is close, but no
cigar.
Curiously, though, if the claim is googled rather than pubmedded, references to such a
finding by (yes) the neurophysiologist Simon LeVay and the neuropsychologist Sandra
Witelson turn up. For example, LeVay is described in an article by Chandler Burr in the
_The Atlantic Monthly_ in March, 1993 as carrying out an MRI study of the corpus callosum
and sexual orientation. Some reports are even more specific. An article at the gayline
website (http://www.gayline.gen.nz/natural.htm) says that LeVay discovered that the corpus
callosum "was bigger in gays than straight men".
Since I could find no such study, I went right to the top, and wrote to Dr. LeVay. Through the
magic of the Internet, he replied almost immediately. He said he never made any such
discovery and never published on the topic. He did say that at one time he worked on an
MRI study, as reported by Burr, but they didn't obtain any clear results and didn't publish it.
So where did the misinformation come from? Another site repeats the exact passage I
found at the gayline website, but this time credits it to the book "Mapping the Brain" by Rita
Carter, from where gayline probably copied it without attribution. We have the book in our
library, but it's out at the moment, so I can't check to see how she came to provide this
misinformation.
What about the claim about Sandra Witelson's finding (at McMaster, from whence I come)?
For example, Maclean's Magazine (the Canadian _Time_ wannabe) for January 22, 1996
(available on-line at the Canadian encyclopedia) says "Witelson and her research partners
illustrated another dimension of brain differences in November, 1994. In a study involving
21 people, they showed that part of the corpus callosum in the brains of some homosexual
men was 13 percent larger than in the heterosexual men".
Seems too specific to be made up. But where's the pub? Dr. Witelson hasn't yet replied to
my query. But I've discovered in the meantime that this refers to a presentation she made
with Scamvougeras as first author at the Miami meeting of the Society for Neuroscience in
1994. I can't get the abstract, but it was cited as recently as 1993 by Rahman and Wilson
who say the study was MRI and confirm the Maclean's account. Given the potential interest
in such a finding, I find it peculiar that they never published it.
Stephen
References
Allen, L., & Gorski, R. (1992). Sexual orientation and the size of the anterior commissure in
human brain. Proceedings of the National Academy of Science, 89, 7199-7202.
Rahman, Q., & Wilson, G. (2003). Born gay? The psychobiology of human sexual
orientation. Personality and Individual Differences, 34, 1337-1382.
Scamvougeras, A., Witelson, S. et al (1994). Sexual orientation and anatomy of the corpus
callosum. Society for Neuroscience Abstracts, 20, 1425.
______________________________
Stephen L. Black, Ph.D.
Department of Psychology
Bishop's University
Lennoxville, QC J1M 1Z7
Canada
***@ubishops.ca
Dept web page: www.ubishops.ca/ccc/div/soc/psy
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