Path: utzoo!attcan!uunet!husc6!tut.cis.ohio-state.edu!saqqara.cis.ohio-state.edu!diana
From: diana@saqqara.cis.ohio-state.edu (Diana Smetters)
Newsgroups: comp.ai
Subject: Re: Left vs. Right Brain <==> Reason vs. Mysticism ?
Message-ID: <32342@tut.cis.ohio-state.edu>
Date: 23 Jan 89 19:12:39 GMT
References: <1511@tank.uchicago.edu>
Sender: news@tut.cis.ohio-state.edu
Reply-To: Diana Smetters <diana@cis.ohio-state.edu>
Organization: Ohio State University Computer and Information Science
Lines: 70

To add a few small points about the discussion on lateral specialization
in brain function, Minsky, and mysticism:

In article <1511@tank.uchicago.edu> staff_bob@gsbacd.uchicago.edu writes:
< (Minsky)
< >My own theory of what happens when the cross-connections between those brain
< >halves are destroyed is that, in early life, we start with mostly similar
< >agencies on either side. Later, as we grow more complex, a combination of
< >genetic and circumstantial effects lead one of each pair to take control of
< >both.
< 
< An interesting theory, which has been disproven any number of times. See,
< for example, the chapter entitled "Infant Cerebral Asymmetry", by Dennis
< Molfese, which appears in the book "Language Development and Neurological
< Theory" (Academic Press 1977). The fact is that we can find evidence of
< hemispheric specialization in very early in life. 

I have a question about arguments which mention that hemispheric
specialization is present "from the start" or "very early in life"
and then go on to use the presence of this specialization to deduce that
such specialization is innate. Namely: how early is "very early" -- if
you consider the fact that evidence that a particular pattern of hemispheric 
specialization is present in the 2yr old child, or even the 3 month
old infant does not constitute evidence that such specialization is
genetically predetermined. A 3 month old infant has already been subject
to a large number of "environmental" influences -- both at the level
of the uterine environment and at the cellular level, in terms of the
chemical influences on the migrating neurons. 

I don't want to argue against the point that hemeispheric specialization
is, to at least some degree, genetically determined -- I just want to
emphasize the point that mounting evidence indicates that environmental
effects on development occur much earlier than is usually considered
in arguments of the form "x is true of small children/infants, so x must be
genetically determined".

In addition, I wish to mention that the fact that all individuals seem
to undergo some pattern of hemispheric specialization does not mean that
all individuals undergo the *same* pattern of hemispheric specialization.
(See Geschwind and Galaburda: "Cerebral Dominance" and "Cerebral
Lateralization").

< To be fair, I believe that it is safe to say that the left brain is
< not exclusively logical, nor is the right brain completely analogical.


Lastly, and most emphatically: the evidence to date concerning cerebral
lateralization has focused primarily around lesion studies. There is
evidence of such things as: lesions to areas of the left hemisphere
(ex. Broca's area) tend to produce certain types of language dysfunction.
From this, one can deduce things like "many aspects of language function
may be carried out by the left hemisphere (in most people)". This
does not give any evidence for the claims that the left hemisphere
is logical/analytical, while the right is concerned with creativity,
art, etc. If anyone could give me references that show this sort of
lateralization of higher cognitive functions like "logical thought",
"creativity", "aesthetics", etc., I would really appreciate it. The
fact that the left hemisphere may handle the bulk of low-level language
processing, and that the right may handle spatial processing and the
generation of mental images (to be kept strictly distinct from the
process known as imagination), does not seem (to me, at least) to constitute
evidence for the lateral specialization of any of the high-level
cognitive processes which have been discussed here (under the denotation
"mysticism").

	--Diana Smetters
	  OSU Laboratory for AI Research
	  diana@cis.ohio-state.edu