They really need to get out more, dissect a frog brain or something, if they’re still clinging to that triune brain nonsense. According to Salon, some psychologists still think that’s valid. The author summarizes an article that…
…addresses (and debunks) one of the most commonly-used metaphors in evolutionary psychology, the idea that the human brain evolved from lower life forms and hence has evolutionary remnants from those animals — akin to an onion with layers.
If you’ve ever heard someone speak of you possessing a “lizard brain” or “fish brain” that operates on some subconscious, primal level, you’ve heard this metaphor in action. This is called the triune-brain theory; as the authors write, the basic crux of it is that “as new vertebrate species arose, evolutionarily newer complex brain structures were laid on top of evolutionarily older simpler structures; that is, that an older core dealing with emotions and instinctive behaviors (the ‘reptilian brain’ consisting of the basal ganglia and limbic system) lies within a newer brain capable of language, action planning, and so on.”
Whoa. That’s silly. Of course, I have an edge: my early career in graduate school was spent studying the neuroanatomy and physiology of fish, and yes, they have a hindbrain, midbrain, and forebrain — all the pieces are there, they develop to different degrees in different lineages, and there aren’t linear ‘steps’ in evolution where, all of a sudden, there are jumps to whole new brain architectures appearing. Even before that, as an undergraduate taking neuroscience from Johnny Palka, I recall how insistent he was that we had to regard the brain of Drosophila as both existing and capable of sophisticated processing. (It’s true, some people think insects don’t have brains. They’re wrong.)
I wonder if this is another consequence of the belief in Haeckel’s erroneous ideas. I’ve skimmed through Dr Spock’s Baby Book, and was surprised to see how much rekapitulationstheorie saturates that book. The creationists love to claim that introductory biology texts teach it as fact, when my experience is that they explain how it’s wrong; they should look into the child psychology texts if they want better examples of a bad idea being promoted today.
So I had to look into the paper described in the Salon article. It’s titled “Your Brain Is Not an Onion With a Tiny Reptile Inside”, which is excellent. It gets right down to addressing the misconception from the very first words. The abstract is also succinct and clear.
A widespread misconception in much of psychology is that (a) as vertebrate animals evolved, “newer” brain structures were added over existing “older” brain structures, and (b) these newer, more complex structures endowed animals with newer and more complex psychological functions, behavioral flexibility, and language. This belief, although widely shared in introductory psychology textbooks, has long been discredited among neurobiologists and stands in contrast to the clear and unanimous agreement on these issues among those studying nervous-system evolution. We bring psychologists up to date on this issue by describing the more accurate model of neural evolution, and we provide examples of how this inaccurate view may have impeded progress in psychology. We urge psychologists to abandon this mistaken view of human brains.
Then Cesario, Johnson, and Eisthen name names. They show that this misbegotten misconception is a real issue by going through the literature and introductory textbooks.
Within psychology, a broad understanding of the mind contrasts emotional, animalistic drives located in older anatomical structures with rational, more complex psychological processes located in newer anatomical structures. The most widely used introductory textbook in psychology states that
in primitive animals, such as sharks, a not-so-complex brain primarily regulates basic survival functions. . . . In lower mammals, such as rodents, a more complex brain enables emotion and greater memory. . . . In advanced mammals, such as humans, a brain that processes more information enables increased foresight as well. . . . The brain’s increasing complexity arises from new brain systems built on top of the old, much as the Earth’s landscape covers the old with the new. Digging down, one discovers the fossil remnants of the past. (Myers & Dewall, 2018, p. 68) [no relation –pzm]
To investigate the scope of the problem, we sampled 20 introductory psychology textbooks published between 2009 and 2017. Of the 14 that mention brain evolution, 86% contained at least one inaccuracy along the lines described above. Said differently, only 2 of the field’s current introductory textbooks describe brain evolution in a way that represents the consensus shared among comparative neurobiologists. (See https://osf.io/r6jw4/ for details.)
Not to blame only psychologists, they also point out that Carl Sagan popularized the idea further in The Dragons of Eden. I hate to puncture the warm happy glow Sagan’s name brings to many of us, me included, but that was a bad book. Don’t ask an astronomer to explain brain evolution and consciousness, ever. I’m looking at you, Neil.
The authors illustrate the misconception well. It’s a combination of errors: the idea that evolution is linear rather than branching, that humans are the pinnacle of a long process of perfecting the brain, and that we possess unique cerebral substrates to produce human capabilities. It isn’t, we aren’t, we don’t.
I’m kind of disappointed that this obvious flawed thinking has to be pointed out, but I’m glad someone is explaining it clearly to psychologists. Can we get this garbage removed from the textbooks soon? Or at least relegated to a historical note in a sidebar, where the error is explained?