> So you are saying that the size of a particular part of the brain may be
> correlated with enhancement in a particular form of intelligence.
Well, no actually that is not what is said. What the author says is
that Einstein had an unusually large parietal region which may point
to such region being involved in 'intelligence', from which does not
follow the definitive conclusion big brain = ++intelligence
So, given
> that you are only interested in differences > or = to 2 SD's from the
> control mean (males with an IQ of 116), we must assume that this increase in
> the *size* of one part of Einstein's brain was either at the expense of the
> size of another part of his brain, or was not enough to push his otherwise
> average/small brain to 2SD's larger than the mean of your controls.
>> Are all abnormally large sizes of a given part of the brain correlated with
> abnormally (and to an equivalent extent) small sizes of another (e.g.
> neighbouring) part of the brain, so that the size-differences cancel each
> other out ? I assume that this is not the case.
>> Assuming, for the sake of simplicity, that there are n forms of intelligence
> that are each associated with one particular part of the male brain, then
> surely it is conceivable, and it will often occur, that some of these parts
> will be, say, 5% larger than the male population mean, and some will be 5%
> smaller -- and sometimes parts will be 10% or 15% or even 20% larger or
> smaller than the mean. It seems to me obvious that, in some individuals,
> the sum of these differences will result in a brain that is significantly
> larger or smaller than the mean, and that we should expect this to be
> correlated, respectively, with a higher or lower IQ, since the IQ is the sum
> of scores in sub-tests of various forms of intelligence.
well thats also making the huge assumption that everything else (such
as cell density remains the same) maybe its particular circuit
arrangements that are responsible for intelligence and not neuron
number per se. You are unfairly taking tentative data and conjectures
due to the original author and making definitive conclusions from them
>> I would be very grateful to hear your comments on these matters."
>> What I am leading up to here is that the above webpage tries to ignore size
> and concentrate on structure, for the simple reason that the two authors are
> both female, and we all know that the average female brain is smaller than
> the average male brain. If the female brain is smaller than the male brain,
> then this must be either because all of its parts are scaled-down versions
> of the equivalent parts of the male brain, or because there are
> size-differences of various sorts between the various parts of the two types
> of brains (including even the absence of one or more parts of the brain in
> the male or the female brain), such that these differences, in toto, result
> in a female brain that is smaller than its male equivalent.
>> If the fact that one part of Einstein's brain is 15 % larger than the mean
> for a sample of brains that output a mean IQ of 116 is causally connected to
> his "genius" (or whatever word you want to use), then there is a prima facie
> case to investigate, as regards the size-difference between male and female
> brains. In other words, if size mattered for Einstein versus the rest of
> us, we would not be wasting our time following up the idea that it might
> matter for male brains vs female brains. I gather from the radio interview
> I heard that big men don't have bigger brains than small men, and big women
> don't have bigger brains than small women -- so it's not a question of
> body-size that's at issue here.
You cannot on the one hand take the example of Einstein as an 'unusual
case' to make your point and then subsequently generalise that to
every other male who is clearly not Einstein. You also assume that
the control data is correlated such that bigger brains => higher IQ,
which may not in fact be true at all from, the sparse info given. Not
only are you supposing enough about the Einstein data (did he actually
have a high IQ?, it is not certain even though he was a "genius") but
also a great deal about the controls
> Now, it may well be that women's mean IQ is found to be the same as men's
> mean IQ, but, in view of the above discussion, that result would have to be
> a bit suspect.
Again you are drawing too much from the data, the increased size may
have nothing to do with Einsteins intelligence and may simply be
coincidental (given that you are only looking at one case)
I have read other research which shows that Einstein had no more
neurons than the average but did have an unusually elvated number of
glial cells. Perhaps this increased partietal cortex was due to this,
but perhaps this is a highly unusual reason for having an increased
brain size, the most common difference between women and men simply
being changes differences in cell/volume ratios.
You are trying to connect two facts as causal without any evidence for
it. Einstein was also dyslexic, is the posterior parietal enlargment
(given its involvement in vision) instead responsible for this with
some weird circuitry in the frontal lobes responsible for is
intelligence??
