Sunday, January 03, 2010

Uncommon Descent Contest 18 Ancient reptile brain explains human psychology? - winner announced

Here's the contest.

The question arose from my longstanding puzzlement over claims that reptile behaviour could be sharply demarcated from bird or mammal behaviour, according to a tri-partite brain organization. The evidence did not seem to support that. For example, if we use a crude, obvious measure like looking after young, well, many crocodilians (including the Mississippi alligator) are pretty good at it.

Perhaps most reptiles are not. I do not myself plan to conduct a household census among snapping turtles and vipers. But if any species of reptile can do it, the simple three-part claim about the brain seems suspect.

"Aidan" at 3 is the winner, and needs to be in touch with me at, to receive his prize.

My only comment is this: If I were a member of a jury that had to decide whether to convict someone of a criminal offence, I would be on my guard immediately when I heard anything about the "reptile brain." So far as I know, if a reptile did it, the reptile's keeper could get a fine for keeping a dangerous animal. That is way less serious than what happens if you are considered morally responsible, instead of unfit to plead, stupid, or something similar.

Meanwhile, I appreciated Collin's comments at 1 and : 2. Re 1: I fear the boy probably did lose his hand/arm or else the use of it, and my purpose in linking to the video was to disadvise foolish stunts with crocodilians. This is unrelated to claims about the "reptile brain" - I would say the same about bears, tigers, or chimpanzees, all of which have inflicted unexpected injuries for no apparent reason. Why risk serious disability to find out that an animal can be unpredictable?

Re 2, it sounds like Collin's in-law is a wise man.

Now here is Aidan's post, a couple of comments interspersed:
The “triune brain” theory (MacLean, 1970) presents the brain in terms of three successive layers:

1) the proto-reptilian system of spinal cord, brain stem, diencephalon and basal ganglia, which controls all genetically-programmed survival behaviours and a range of basic physiological functions such as heartbeat, breathing, digestion, et cetera;
2) the paleo-mammalian ‘limbic’ system, comprised of amygdala, hypothalamus and hippocampus, which generates self-awareness and attendant emotional responses; and
3) the neo-mammalian cerebral cortex, responsible for foresight, insight, reason, speech, et cetera.

MacLean’s model was an attempt to show that the evolutionary inheritance of modern human beings could be directly discerned in the structure of our brains. On the face of it, this seems a reasonable enough approach since, if we are indeed the transitory outcome of an on-going evolutionary process, the evidence ought to be visible within our physiology. As with every evolutionary artefact, however, the theory does not appear to have held up over time and is now outmoded, at least from a neurobiological standpoint. Against the predictions of Maclean’s theory, ‘mammalian’ social and parental behaviours show up in a wide range of non-mammalian vertebrates. Indeed, birds are demonstrably in possession of their own ‘limbic’ structures and reptiles appear to be, too.

[Which is why I would not recommend anyone to interfere with egg-laying vertebrates protecting their eggs, on the theory that those creatures can't - on principle - care - d.*]

The notion of evolution to which the triune theory adheres is ‘pre-synthesis’ – it postulates the addition of novel structure upon novel structure in a linear fashion. The ground of ‘orthogenesis’, however, which presented evolution as steadily progressive, has long since been lost. In the post-synthetic world, those sticking determinedly to evolutionary explanations for the origin and development of life see the process as proceeding mainly through adaptation of pre-existing structures. Three big slabs of systemic independence loosely knitted together would be a crude violation of this, and of the organic interrelatedness of all parts of the brain.

[My own view is that life forms use the brain capacity they have to do their jobs. - d.]

Clinical and ‘pop’ psychologists together and, of course, the lay media, are among those who like the three-brained idea. The concept of mental triplicity does appear to be useful to many people in practice, not as an accurate description of the material organisation of the brain but of the dynamic architecture of the mind as encountered from within. The notion that humans exist upon three ‘planes’ – material, psychic and spiritual – can be found in many traditions and also corresponds to Plato’s tripartite view of the soul. An idea so enduring may well be reflective of something essentially and immutably true.

[Maybe. I don't know. In my experience, "pop" psychologists are looking for "Get out of jail free" cards. "Reptile brain" is as good as the next excuse. We are only beginning the search for real answers.]
(*Note: As a child, I sometimes wandered through swampy areas. One would sometimes be assailed by a male red-winged blackbird- for no apparent reason. Later, it became clear that he was protecting a nest.)