From: rowe@lepomis.psych.upenn.edu (Mickey Rowe)
Newsgroups: k12.ed.science
Subject: Re: sexual preference
Date: 6 Jan 93 21:33:39 GMT
Organization: University of Pennsylvania

In article <35361.2B4AA22D@puddle.fidonet.org>
     Rebekah.Lawrence@p0.f14.n346.z1.fidonet.org (Rebekah Lawrence) writes:

>I have recently been hearing various reportsd on homosexuality being
>a result of a brain defect.

Is this really how it was reported to you?  As a "defect"?  I'll
return to this point below.

>...There have been explanations saying homosexuality is not a choice,
>but a problem one can not help.  I know very little about this
>subject.  I have read a couple articles  describing the difference
>between the brain of a homosexual and that of a "strait"
>individual.  The size was the defect.  

You may know about as much as there is to know on the subject.  The
principal researcher into this topic is a man named Simon LeVay.  He
went searching for differences in size amongst particular brain nuclei
(in neuroanatomy, a nucleus is a collection of nerve cell bodies in
the brain) in humans as a result of some other studies performed on
rats.  

Rats with lesions in a small nucleus in a particular region of the
hypothalamus will exhibit behaviors that our inappropriate (I mean
"inappropriate" in a biological sense, not a moral sense) for their
sex.  In particular, male rats will allow other male rats to mount
them if an experimenter has damaged the cells in this nucleus.  LeVay
reasoned that the homologous nucleus might perform similar functions
in humans.

To gain evidence in support of his hypothesis, LeVay collected the
brains from a variety of men, both gay and straight, and measured the
size of this nucleus.  He found that in gay men and in women (of
indeterminate sexual preference, I think) the group of cells in
question was on average smaller than in straight men.

I want to caution you about a few things with regards to this and
similar studies.  First from the perspective of the science: the
nucleus is very small to begin with, and there aren't any labels
written on the brain to tell you which cells are part of which
nucleus.  There are ways of testing what cells go where, but the
possibility for error is large.  LeVay did seem to do one thing well,
to avoid biasing his results, however.  His experiments were double
blind; the people measuring the nuclei didn't know what the professed
sexual preference was of the people they were examining--nucleus size
and sexual preference were matched up after the fact.  LeVay's
conclusion is reasonably well founded, but must be replicated before
other scientists will fully accept it.  Replication may not come soon
since as you say this is a "touchy subject".  Not many people are
willing to face the social pressures that LeVay must endure.

Second, even LeVay is very up front about the fact that causality is
indeterminate here.  That is, he has shown a correllation between the
size of this nucleus and sexual orientation, but he has not
demonstrated a causal connection.  The nucleus could be small because
the man is gay and not the other way around.  Also, the correllation
could arise because both properties are affected by something else
entirely.

Thirdly, there were many outlying points on LeVay's graphs (i.e.
straight men with small nuclei, and gay men with large nuclei).  LeVay
suggests that this could be explained in part by gay men not admitting
their sexual preference (in this society who could blame them), and
some people having gay lifestyles without actually being gay.  If
nothing else, these outliers suggest that the relationship between
brain morphology and sexual preference may not be simple.

Finally, in terms of the social significance, LeVay is hated even by
many gays just for asking the research questions that he's asking.  In
Germany some people have undergone surgery in an attempt to "cure"
themselves of the "affliction" of being gay.  Many gays feel that by
suggesting possible avenues for "curing" them, LeVay is arming
conservative opponents with a weapon to eradicate them.  Science can
describe the conditions under which homosexuality occurs.  It is up to
society to decide if these conditions should be deemed "pathological",
"defective", or "necessitative of a cure".

>Internet: Rebekah.Lawrence@p0.f14.n346.z1.fidonet.org