Michael Sylvester asked:
are there cases of identical twins separated and adopted by differnt
families where both have developed a homosexual lifestyle?
And if one did and the other did not, would that be evidence of
an environmental influence on homosexual behavior?"
I can't give you a citation off hand but the answer to both questions is
"yes." The concordance rate of for homosexuality in MZ twins is about 50%.
i.e., large genetic component but room for non-genetic variables.
ONE WORD OF CAUTION: The fact that the concordance rate is not 100% argues
for "environmental" influences. HOWEVER, let us be clear that in this
context, "environmental" is misleading. What it really says is that there
is room for "non-genetic" variables. For example, exposure to a virus in
utero or in infancy are environmental (i.e., non-genetic) variables but they
are not the sorts of things that most students (or clinicians for that
matter) would readily think of when they hear the word "environmental."
Might I also point out that error variance is also "non-genetic." This may
or may not be relevant in twin stusdies of homosexuality but it's probably
very relevant when discuyssing the genetics of schiz. and/or depression:
i.e., how many twin pairsa are reported as discordant when a better
nosological system would have found the pair to be concordant?
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Edward I. Pollak, Ph.D. Office (610)436-3151
Professor of Psychology Home (610)363-1939
West Chester University FAX (610)436-2846
West Chester, PA 19383 [EMAIL PROTECTED]
Peoples Building Rm 44 www.wcupa.edu
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Husband, father, biopsychologist, herpetoculturist and bluegrass
fiddler........... not necessarily in order of importance.
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