From: Scott Chase (firstname.lastname@example.org)
Date: Thu 15 Dec 2005 - 19:00:59 GMT
In a previous post, I was pretty harsh on the popularized notion of the
triune brain, attributed to Paul MacLean also responsible for introducing
the "limbic system" concept. Joseph LeDoux was critical of MacLean's views
in his _The Emotional Brain_, especially focusing on the questionable
comcept of a "limbic system". LeDoux's criticisms are important and perhaps
in themselves effectively torpedo the idea of a triune brain as envisioned
by MacLean, but in a previous post, my focus ws on the concept of a dicrete
region that one could call a "reptilian brain" (R-complex). First off the
term "reptile" is problematic in classification. It is what some
systematicists would refer to as paraphyletic, failing to encompass
descendant groups such as birds. Everything MacLean refers to a "reptilian"
may better be termed amniotic, which takes all amniotes (turtles, lizards,
snakes, crocodilians, birds, and mammals into account). The basal areas
(basal ganglia, etc) might be better seen as an amniote feature, if that indeed is true. My comparative neuroanatomy is rusty on this detail.
But there may be a problem even with the "amniote brain" concept. LeDoux
lets the cat (or "fish" out of the bag) in _The Emotional Brain_ when he
says (pbk page 98): "All other vertebrate creatures (birds, reptiles,
amphbians, and fishes) have only the reptilian brain". In his review of
MacLean [1990, Science, vol 250, p. 303-] Anton Reiner follows the same
thread saying: "...the R-complex is not a reptilian invention but seems to
be present in vertebrates all the way back to jawless fishes." Thus we might
not even be able to talk about a "gnathostome brain". Perhaps what MacLean
has popularized as the reptilian brain is merely a widespread vertebrate
feature. So not only is the "reptilian" brain a misnomer, but doesn't even
stay confined within the amniotes.
In "Man's reptilian and limbic inheritance" [found in A Triune Concept of
the Brain and Behavior. 1973. University of Toronto Press] MacLean speaks of
the close relation of birds and reptiles, which superficially appears as a
category error, though in an earlier footnote he does break "reptiles" down
to its proper extant groups and mention the actual close relation of birds
and crocodilians. There are various groupings within the "reptiles" besides
crocs and the foggy term "reptile" could vaporize upon closer inspection.
Anyway in this essay MacLean makes a statement that seems relevant to
memetics. He says (p. 10):
[bq] "The reptilian brain seems to be hidebound by precedent. Behaviourally,
this is illustrated by the reptile's tendency to follow roundabout, but
proven, pathways, or operating according to some rigid schedule. Customs of
this kind appear to have some survival value and raise the question as to
what extent the reptilian counterpart of man's brain may determine his
obeisance to precedent in ceremonial rituals, religious convictions, legal
actions, and political persuasions." [eq, MacLean's self-reference to
previous work omitted]
One wonders what determines our propensity to follow a tradition as set in
stone as the "limbic system" concept (see LeDoux) or the "triune brain"
concept. This, in itself, might be a good study for memetics on how popular
psychological notions have spread through our culture and impacted other
realms of thought. How widespread is the "triune brain" concept and how
seriously is it taken?
After the above quoted passage, MacLean makes an interesting reference to
site fidelity in sea turtle females laying their eggs in some strange sense
portraying this activity as obsessive-compulsive as if turtles are
manifesting an ancient form of OCD when they return to the same beaches. I'm
speechless. MacLean does earlier make the point that the turtle's brain is
structurally close to that of protomammalian reptiles, though his favorite
subject of lizards are better to study behaviorally, even though lizards are
just convenient surrogates for our ancestors.
Returning to MacLean's theme of the cultural aspects of our reptilian brain,
in a later work he talks about "isopraxic behavior" (imitation, mimicry,
social facilitation...). I like the term isopraxis. MacLean says [page 239,
The Triune Brain in Evolution, 1990, Plenum Press, New York]: "Since
destruction of parts of the R-complex in both lizards and monkeys interferes
with display behavior, it might be inferred that the corresponding [MacLean
dislikes "homology"] structures in each species are implicated in
conspecific recognition and the expression of isopraxic behavior."
There's a point in MacLean's above cited "Man's reptilian and limbic
inheritance" where he waxes protomemetically. This book was published in
1973 but the actual lecture may have occurred in 1969. He says (page 20):
"Indeed, it is questionable whether or not the human race could survive without limbic emotions because, whatever else they do, they assure conflict and argument which in turn insure the mixing of the gene pool of ideas!"
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