As Terrance Deacon notes in his wonderful work, The Symbolic Species, if it
were simply brain body mass ratios all dwarfs would be geniuses. The model
is old and outdated, and forgets things like the fact that birds are tiny
tightly compressed neurons ... . Crows are very smart, just try shooting one
of the bastards and have a look at the studies of a West Australian
Naturalist on crows, not to mention the finding of their use of tools in PNG
(right shaped twigs)... .
John H.
Richard Norman <rsnorman at mediaone.net> wrote in message
news:fc90qto7oj3lpdmsf6vb2jmrjanvrc6phs at 4ax.com...
> On Wed, 12 Sep 2001 17:49:36 -0500, "Miles Robinson"
> <m-robinson7 at northwestern.edu> wrote:
>> > I have a basic question about brain mass studies. It has been
supposed
> >that the brain mass to body mass ratio can give realtively good
quantitative
> >measure of "intelligence". However, when looking at the brain as a
control
> >system for the body, it's hard to overlook that fact that a larger body
mass
> >does not necissarily require a larger brain to maintain equivalent
> >functionality. For example, a single muscle doesn't require more neurons
as
> >it gets larger during the evolutionary process as far as I can see. I
reason
> >this way because an entire muscle moves together and thus the whole organ
> >gets the same signal from the brain, so why is it necessary for multiple
> >neurons to control something that only requires as single signal? Is it
not
> >more reasonable to use the critera of number of organ systems or
sub-systems
> >vs. brain mass to quantitatively evaluate intelligence? Or better yet the
> >number of body systems to brain divisions?
> >
> >Thanks
> >Your attention appreciated
> >EE student at Northwestern U.
> >(Not a neuroscience student)
>> I seriously question your supposition that brain mass/body mass ration
> correlates with intelligence. Do you have citations for that?
> Certainly you are not suggestive a correlation over the range of
> ratios exhibited by human variability!
>> Also, a "muscle" does NOT act as a single signal. Vertebrate muscles
> are composed of motor units, each controlled by a single motor neuron.
> Large muscles tend to contain more motor units, that is more neurons,
> to control them. The division into motor units is important in
> maintaing fine control of magnitude of contration. There also may
> some limit on the size of a motor unit -- the number of muscle fibers
> that a single motor axon is capable of innervating. This may be a
> support infrastructure limitation -- how much transmitter is the axon
> capable of producing and releasing? Again, this requires large
> muscles to contain more motor units.
>> According to your argument, a whale should have the same size brain
> as, say, a shrew. It has the same number of organ systems and organs
> which do pretty much the same things. So the same size brain should
> be capable of managing a mammalian body, no matter the size.
>>
