37966[evol-psych] Re: Re: IQ tests
- Sep 1, 2005
> Julian O'Dea: Why must there always be an adjustment forThe distinction has proved meaningful in the evolutionary study
>body size? I have never understood the force of this argument.
>Larger is larger, isn't it?
of intelligence between absolute brain size and EQ
(encephalization quotient) which is a measure of brain size over
and above what is predicted from body size (or what is
considered needed for basic "house-keeping"). The
assumptions pan out rather well. Harry Jerison's 'Evolution of the
Brain and Intelligence' is still a classic:
That's for between-species comparisons. Now within-species,
or at least within the human species this doesn't appear to be
the case (but again the IQ/brainsize correlation in humans may
be spurious). Here are statements from the 'Handbook of
"Brain size is not related to body size in humans"
pg 241 chapter 11. H. Jerison
"contrary to what is sometimes claimed, no study of brain
volume (or head size) has shown a substantial decrement in
correlation after partialling out either height or weight (or both)"
pg 246 chapter 12. P. Vernon et al
> As for the intelligence of Homo floresiensis, as I pointed outNo birds have small bodies, and homo floresiensis has a very
>at the annual meeting of the Australasian Society for Human
>Biology last year, parrots and other birds are proving to be
>surprisingly intelligent despite their small brain size.
>Presumably it is a matter of efficient packaging.
low EQ. Here's Richard Dawkins:
"Biologists expect small animals to have small brains anyway
and they have developed ways of calculating this. The EQ or
Encephalisation Quotient is a measure of how much bigger (or
smaller) a brain is than it "ought to be" for its body size, given that
it is, say, a mammal.
Calculated in this way, modern humans have an EQ of about 6,
meaning that our brain is six times as big as it "ought to be" for a
mammal of our size. Homo erectus is believed to have an EQ of
about 4, and Australopithecus (our probable ancestors of about
3m years ago) about 2.5 or 3 (similar to a modern chimpanzee).
Flores woman comes into the same range as Australopithecus
or modern chimpanzees. "
So Flores has tools like an erectus but is encephalized like a
chimp or Lucy. As for birds, EQ matters, as a big study that just
came out this year shows:
"They gathered data on brain mass for 1,967 species.
In more than 600 introductions of nearly 200 bird species into
new habitat they found that species with brains large relative to
their body size tended to survive better in new environments than
Examples include the introduction in the 19th century of the
European starling to North America.
"Overall, our results provide strong evidence for the hypothesis
that enlarged brains function, and hence may have evolved, to
deal with changes in the environment," they wrote in this week's
issue of the Proceedings of the National Academy of Sciences.
The researchers last month published an IQ index guide to birds
that show corvids birds from the crow family including ravens
and jays are by far the cleverest birds.
Next on the list are hawks, woodpeckers and herons, while
partridges, new world quails, emus and ostriches are the dolts
of the bird world."
This study is interesting because it added external validity to
animal intelligence tests (similar in content to human
intelligence tests) which also showed a connection between bird
species performance and EQ (same for primates).
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