Loading ...
Sorry, an error occurred while loading the content.

37966[evol-psych] Re: Re: IQ tests

Expand Messages
  • Jason Malloy
    Sep 1, 2005
      > Julian O'Dea: Why must there always be an adjustment for
      >body size? I have never understood the force of this argument.
      >Larger is larger, isn't it?

      The distinction has proved meaningful in the evolutionary study
      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
      Human Intelligence':

      "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 out
      >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.

      No birds have small bodies, and homo floresiensis has a very
      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
      smaller-brained birds.

      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).
    • Show all 10 messages in this topic