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From: demers@beowulf.ucsd.edu (David E Demers)
Newsgroups: comp.ai
Subject: Re: IQ is not static, genetic differences inconsequential.
Summary: twin studies have good data
Message-ID: <6899@sdcsvax.UCSD.Edu>
Date: 30 Jul 89 21:18:10 GMT
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Reply-To: demers@beowulf.UCSD.EDU (David E Demers)
Organization: EE/CS Dept. U.C. San Diego
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In article <GHH.89Jul30091639@cognito.princeton.edu> ghh@cognito.princeton.edu (Gilbert Harman) writes:
>In article <504@dcdwest.UUCP> benson@dcdwest.UUCP (Peter Benson) writes:
>* I have seen studies that note a significant correlation in
>* IQ between twins raised apart.  If it is all 'learnable and
>* teachable' then there would be no such correlation.
>
>and others have referred to this without challenging it.
>But what studies are being referred to.  A few years ago it
>emerged that Cyril Burt's classic twin studies were faked.
>(Leo Kamin demonstrated that the numbers were too good to be
>true and then Burt's son reported that his father had indeed
>faked the results.)  This leaves the question whether in
>fact there are studies indicating a significant correlation
>in IQ between twins raised apart.  If anyone knows of such
>studies I would be interested in references to them.

I unfortunately don't have a reference handy, but I went to
a talk this year on the current studies underway at {Michigan|
Minnesota} on identical twins reared apart.  Much has been
published, so a few minutes at the library should get you pointers.
I'll try to get some references tomorrow and post...

My recollection of the talk was that there were somewhere in
the order of 100 sets of identical sets of twins reared apart
(+/- 50%), plus about the same number of fraternal twins
reared apart, plus about the same number of each reared
together.  Each set of twins underwent about 50 hours of
testing, ranging from physiological to various "personality"
type tests, over the course of 9 days in the University lab.

The results to date show tremendous correlations along nearly
all tests - identical twins having far stronger correlations
than fraternal.  In fact, the proportions were appropriate
to match up with the amount of genetic similarity.  Controls,
unrelated persons of approximately similar backgrounds (obviously
it's impossible to find enough people who match on the non-genetic
factors to isolate everything...), showed nearly no correlation,
while identical twins were correlated at approximately twice
the level of fraternal twins.

Please don't flame my cavalier usage of "correlation" here, as
a twin I thought it would be an interesting talk and am reproducing
it all from memory... and I'm not an expert on experimental
statistics (nor very literate in the area...).

So, to make a short story long, it does appear that there is
SIGNIFICANT genetic component to IQ, as well as to many other
parts that make up us humans.

I prefer to use a working philosophy that genetics provides
a range of potential.  Development determines where in that
range we end up.  

Dave "He had potential" DeMers
Dept. of Computer Science & Engineering
UCSD
La Jolla, CA 92093
demers@cs.ucsd.edu