Three-Brain Theory Questioned


For years, many scientists and writers have divided the human brain into three evolutionary stages: the reptilian brain (brain stem and cerebellum); the limbic brain (the amygdala, hippocampus, and other structures associated with emotions in mammals); and the neocortex (associated with language, abstract thought, and other advanced primate functions). This division has filtered through to the popular press and marketers, who sometimes talk about “appealing directly to the reptilian brain”. Usually such appeals are related to very basic functions, like sex.

One of the assumptions about the so-called reptilian brain is that it has no role in emotions. Indeed, crocodiles and other reptiles don’t seem to exhibit much social or emotional behavior. In The unfeeling reptilian brain: Don’t mess with its babies, writer Denyse O’Leary questions that assertion. She cites an alligator expert who has found that alligators will respond to the simulated sound of a baby alligator in distress. This seemingly altruistic behavior may indicate that there’s more going on in the reptilian brain (do amphibians have just reptilian brains?) than previously thought.

The article suggests that the gators are exhibiting curiosity or may be trying to defend a young member of their species. One other possibility that occurs to this cynical mind is that perhaps the adult alligators drawn by the baby-gator-in-distress sounds are just hungry… that would take us back to the pure reptilian brain level.

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