brain size and intelligence

George Hammond ghammond at
Fri Feb 16 21:10:06 EST 2001

Richard Norman wrote:
> "MS" <marshmallow5 at> wrote in message
> news:5y4g6.456$WV5.59588 at
> > Since a relationship exists between brain:body ratios and intelligence
> > across species, any thoughts on why it doesn't pertain within a species
> > (i.e. humans). Or are there studies demonstrating this which I'm not aware
> > of?
> I believe that historically there were attempts to correlate
> brain size with "race" and thereby establish "objective
> criteria" for racial superiority theories.

Naw.. you wouldn't be that lucky.

> One major problem is defining what you mean by "intelligence"
> and demonstrating that a single indicator can measure whatever
> you mean by it.

Start with mental speed of information processing in
bits/second... it's already been proved to be the dominant
biological component of intelligence in humans.

> Another major problem is that even a modest correlation allows
> enormous numbers of individual cases where the relationship
> is false.  So any result based on population data is totally
> worthless when applied to individuals.  Therefore there is
> no real utility in even attempting the study on humans.
>  It would not be a useful indicator for anything.

Wrong.  This statement is nothing but aggrevated line
professional pedantic academic propaganda.  Ignore it.

> A third major problem is that to establish significant results
> for even a modest correlation, you need data over a very wide
> range of brain sizes and "intelligence" (whatever that is).

Intelligence is mental speed in bits/second (see Eysenck,
Roth, Jensen, Vernon etc. etc. etc.)

> Normal humans don't have enough variation in brain size.

Third World nutritional growth stunting shows stunting of
brain size by up to 50%... the impact on IQ is proportional...
they can actually measure someone's IQ deficit by wrapping
a tape masure around their head in some chronic starvation

> You can get a wide variation in brain size by looking across
> species.  A similar problem is seen in looking at the relation
> between body size and metabolic rate.  Within one species,
> there is not really enough variation to firmly detect whether
> the power law relationship has an exponent of 2/3 or something
> closer to 0.7.  But across a wide enough range of body sizes
> (which requires a very diverse range of organisms) you can
> clearly see that the exponent is distinctly greater than 2/3.

measuring metabolism and body size is for amateur mechanics.
Where you seperate the men from the boys is when you attempt
to measure psychological variables such as Intelligence and
Personality.... and the FIRST AXIOM of such research is to
IGNORE any litany put forward by 2nd-string academic line
professionals.... like Jesus avoided the Pharisees.

George Hammond, M.S. Physics
Email:    ghammond at

More information about the Neur-sci mailing list