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Re: IQ & EQ



 Bill Adlam <wa105@mead.anglia.ac.uk> wrote:

> It is encephalisation quotient which has been found very roughly to
correlate 
> with 'intelligent' behaviour.  When two closely related species have
great 
> differences in intelligence (e.g. humans and chimpanzees), they almost
always 
> have great differences in EQ.  But relatives such as tigers and tabby
cats, 
> with different brain sizes (absolute or divided by body mass) but about
the 
> same EQ, have similar behaviour.

Good points.  Indeed, the housecat appears _much_ brainier than its larger
relatives, but this seems to be purely a function of size.  And the
anatomical similarity of the lion brain and the tiger brain would suggest
that one could not deduce from the brain alone which is the pack hunter and
which hunts solo.

_The Encyclopedia of Dinosaurs_ includes a number of articles pertinent to
the discussion.  Dale Russell's _Intelligence_ paper, for example, cites H.
J. Jerison's _Evolution of the Brain and Intelligence_ for the formula
which states that "brain weight in living animals is approximately
proportional to the two-thirds power of body weight.  Thus, because
dinosaurs were on average much larger than living animals, their brains
only appear to be unusually small.  In fact, brain-body proportions in 10
species of dinosaurs, when corrected for body size effects, were comparable
to those of living reptiles."  He goes on to say that he determined that
two late Cretaceous theropods from Canada had brain-body proportions
comparable tothose of ratite birds.

Under the heading, _Paleoneurology_, Emily Buchholz writes:
Brain size is negatively allometric relative to body size, following the
power function E = kPx, where E is brain size, P is body size, k is a
constant equal to the y-intercept on a log-log plot (Jerison, 1973; Hopson,
1977).  The slope (x) of the regression line defined by this function
varies modestly among vertebrate classes (and also among authors), but is
very close to 0.67.  Y-intercepts vary by a power of 10.  Birds and mammals
have brains approximately 10 times as large as those of bony fish,
amphibians, and reptiles of the same body size."  With an EQ rating of 1.0
indicating a brain size equal to that predicted on the basis of body size,
she quotes J. A. Hopson's EQ figures for dinosaurs as ranging from 0.2 to
5.8, and Philip Currie is said to have recently calculated "_Troodon
(_Stenonychosaurus_)" to have an EQ of 6.48, within the range of living
birds.  Buchholz goes on to say that the sauropods had the lowest EQs.  

In his _Physiology_ article, Kevin Padian states that "some hadrosaurs, and
especially coelurosaurs" account for the highest figures.  Somewhat in
contrast to the explanation above, Padian states that the 1.00 figure
represents the EQ of an extant crocodile.    He does state, however, that
"the range of dinosaur brain sizes ranks well below those of mammals and
birds," that low-EQ ratites are "not particularly intelligent," and that
there is "not a necessary connection between brain size and physiology." 
Furthermore, he points out that "we cannot be sure that the brain filled
the braincase entirely."  Some estimate that the brain may have filled as
little as 50% of the space.

Emily Buchholz sticks up for the oft-maligned _Stegosaurus_, pointing out
that T. Edinger has found earlier braincase estimates flawed, based on
"incompletely known brain casts of individuals of completely unknown size."
 This information comes as a relief to me, as I was recently puzzling over
the size of the _Stegosaurus_ brain cast at the Academy of Natural Sciences
in Philadelphia.  (Size of a walnut, my foot!  Show me a walnut the size of
a man's fist)!

Buchholz states: "In general, the larger the encephalization quotient, the
more plastic and less stereotypical the behavior of the animal.  This
behavioral flexibility is an approximation of 'intelligence.' "
 
Given the unknowns (actual mass for extinct dinosaurs, lack of very closely
related living animals for comparison), and the fact that so many of the
dinosaurs fall outside the range of living animal size (sauropods most of
all), I believe that there is much we do not know about the intelligence of
these vanished creatures.  But even so, the study of dinosaur braincases
will be very informative in helping us to understand the evolutionary
relationships of the dinosaurs, and the analysis of dinosaur brain
organization helps to give us an understanding of the relative importance
of the various senses for a given species.  And Philip Currie has written
that the large relative size of the cerebellum (especially the floccular
lobe) in troodontids suggests a refined sense of balance.

-- Ralph Miller III     gbabcock@best.com
           
  
> 
> This applies less strongly to distantly related animals, and as a rule of

> thumb performs quite well comparing major vertebrate taxa.