Re: Famous thinkers and their IQs & their head sizes

Timothy Bates (
Thu, 26 Nov 1998 14:37:18 +1100

Hi all

>> Nick Bostrom wrote:
>> > BTW, contrary to what was said on another thread some weeks back,
>> > there seems to be a fairly substantial correlation between IQ and
>> > brain size. I've heard figures of correlation coefficients of up
>> > to .4.
yip. contrary also to everyone's favourite defender of Marxist-Leninist science for the people Steven jay Gould.

>>>It would be interesting to try correlate the size and
>> > complexity of specific cortical areas with performance measures of
>> > the sort of activity they are thought to be responsible for. Maybe
>> > one could find even greater coefficients then.
That is being/has started to be done. People are looking to extract the factor structure of human intelligence from regional cell counts and gray/white matter ratios. Of course, the great bulk of IQ variance is explained by a single factor so these effects struggle under pretty hefty signal to noise ratio.

>> This is probably a stupid question, but how to explain this Brain
>> size/I.Q correlation if we admit that the I.Q level has
>> significantly risen in one century?

One answer (proposed by Jim Flynn, in fact, is that intelligence hasn't risen, while IQ has).

then Remi Sussan said (in reply to nick):
> >A .4 correlation leaves a huge scope for other factors, so I
>>don't see any difficulty here.

difficulty for what: dualist theories on mind?

>(It's also possible to imagine that
>better nourishment during childhood could have increased average brain
That proposal has been tested by the late HJ Eysenck, with some success.

>One has to be careful before jumping to conclusions from a weak

umm. why so any more than with strong correlations? One actually has to be careful jumping to conclusions when there is no theory. There is a well formulated theory of why brain size and structure relates to IQ.

>After all, shoe size also correlates positively
>with IQ (though less than brain size I think).

not very well at all actually. Nose size however, has a good correlation (around .4)

>Couldn't head size
>simply be correlated with body size, which in turn may be correlated
>with intelligence because the best mates prefer to mate people who are
>both tall and intelligent?

That is exactly what is tested in the papers on this matter.

a nice reference is given below. There are by now, however, many dozens of papers on this topic. Steven jay Gould's response is simple denial: fitting really for such an arm chair critic.

Rushton,-J.-Philippe; Ankney,-C.-Davison (1996) Brain size and cognitive ability: Correlations with age, sex, social class, and race. Psychonomic Bulletin and Review. 3: 21-36.

Dr. Timothy Bates                   Don't compromise.  Use QuickTime.
Dept Psychology                     <>
Macquarie University                <>
Sydney NSW 2109 Australia   

Get QuickTime Announce -- your source for QuickTime news and information <>