I feel like hackin’ at the undergrowth today. Get ready for some No’s.

There’s no triune brain. “Lizard brain,” “mammal brain,” that stuff? The notion that basic motions and functions are in the “ancient” (hind) brain, emotional urges and specifically sex and aggression are in the “next” (mid) brain, and thought and reflection and moderation are in the “most recent” (fore) brain? It’s bullshit. You may find references to it being currently “out of favor,” which is more of the same – scientific thinking and theory had nothing to do with its origin and promotion, and they still don’t. You won’t find scientific debate and testing because the idea was nicht einmal falsch, not even wrong, in the first place.The terminology varies, which means nothing to me. Call it the reptile, paleomammal, and neomammal, doesn’t matter. The construction is false because the sectors of the vertebrate brain were not added in succession.

Top views: red/orange = forebrain, green = midbrain, blue = hindbrain; all present & accounted for in every vertebrate

  • The vertebrate brain does display three parts (fore, mid, hind) but all vertebrates have all three. To say it again: a lizard, for example, does not have a brain composed of only hindbrain and midbrain. Mammals’ forebrain features an elaborate neocortex with six layers – more complex and more of it, not a new part.
  • Behaviors do not emerge from any one of the three parts of the brain, and when we do track brain physiology to aggression (for instance), the relevant neurotransmitter activity which in traveling throughout the brain kicks it “on” is forebrain-originated, entirely counter to the triune model.
    • Similarly and significantly, the anatomical area tagged as the so-called limbic system (another invention from the same author) is not some hotly-spewing fount of emotion, but rather a memory-processing and association center.
  • Sex and violence are not more “primitive” or displayed in a disproportionate or unregulated way by nonmammals. Nor do these animals lack social lives and multiple complex cognitive functions.

Where did this notion come from? One guy: Paul MacLean, a central figure in the discipline of U.S. brain research, who despite his accomplishments was clearly untrained in evolution and ecology. He proposed the triune brain in the early 1970s, and it gained traction in Carl Sagan’s The Dragons of Eden in 1977. That’s it. No scientific procedures, publishing, or debate were involved. He made it up, it got popularized, and then it became a commodity.

MacLean was no small potato, especially in terms of professional power. He had headed a research section on midbrain function at the National Institute of Mental Health since 1957 and in 1971 became chief of its Laboratory of Brain Evolution and Behavior. I don’t hesitate to suspect that his status and position shielded the notion (I do not call it an “idea”) from the absolutely explicit takedown it merited up until the modern day. If any of you smarties out there want to investigate that from the perspective of David Hull’s Science as a Process, I think there’s a dissertation in it.

There’s no split-brain. No left-brain/right-brain, not like people say anyway. One side is not the “rational, verbal one” compared to the other side being the “intuitive one.” There is no such thing as a right-brain person or left-brain person which actually stems from brain usage. Doing math, talking, feeling stuff … all of them involve complex activity throughout the two sides of the neocortex.

The famous 1960s work by Roger Sperry and others on hemisphere-separated patients is full of useful observations (the Wikipedia entry is good), however, it does not track to uninjured/un-intervened people. A person with a severed corpus callosum utilizes one side of the neocortex for a particular function as a compensating mechanism, which tells us nothing about how a person with an uninjured brain does it. The asymmetries that have been legitimately observed are variable, nowhere near consistent enough to characterize, and typically complementary regarding the activities in question.

Red = corpus callosum – a very busy place, not a barrier

The key notion too is that talking is somehow more “rational” than drawing or other visual representation, a logical jump which hides a multitude of intellectual misdemeanors. The idea that we think better than other creatures because we can talk, as evidenced (somehow) by the claim that we talk because we think better, is nestled deep, often visible only in the taint it’s laid upon some more overt claim or idea, like this one.

As a merely pedantic point too, this represents yet another example of mistaking the neocortex for “the brain.”

You can thank The Dragons of Eden again, which as a cultural artifact served as an ongoing textbook for pop science, along with Omni magazine, for several generations; and also Betty Edwards’ Drawing on the Right Side of the Brain (1979), which however useful or helpful it may be for actual drawing is unmitigated hogwash regarding brains. Like MacLean, Edwards was a successful academic, and the traction of her constructions could easily go into that dissertation topic I just mentioned.

No % that goes unused. The usual figure is “we only use ten percent,” which dates back at least to the early 20th century, sometimes referring to the mind and somewhere along the way it was applied to the actual matter of the brain or neocortex. Its origin is complex (again, Wikipedia does it right this time), but noting that Dale Carnegie’s notoriously mendacious How to Win Friends and Influence People (1936) played a big part in the cultural traction should tell you all you need. The exact percentage varies a bit via the large-scale cultural telephone game. Its use in popular reference are legion, e.g. Deathstroke the Terminator for you comics fans.

Barry Beyerstein did a great job listing what actual scientific work tells us about brain activity (see the above-linked Wikipedia), which I can summarize coarsely but accurately by saying, “You use your whole neocortex most of the time, every minute you’re alive. Yes, various bits ‘light up’ during various activities but nothing goes dark.”

I don’t really need to go into full debunk mode because fortunately this notion seems to have been scuttled in recent years, probably due to the Mythbusters episode. It continues to appear in the odd movie, e.g., Lucy. I bring up this example on purpose as there, as in many examples, using this “untapped potential” unleashes not merely more brain activity and presumed competence at something (as with Deathstroke) but access to magical, paranormal, or spiritual powers. Take a moment to consider the implications of a magic organ harboring something secret and special.

So much for the branches of evil. How about the root?It lies in the Angel/Ape construction of Victoriana, the notion that human behavior is an ongoing and Manichean struggle between the new and thinking and morally-capable civilized mind and the surging urges we’ve retained from our bestial forebears who roamed about in a haze of unbridled emotions, poor brutes, because they couldn’t help it. This is a deeply-loved myth, reskinned in dozens of different marketable modes like “genes/environment,” “culture/biology,” and “nurture/nature,” none of which were ever built from anything resembling scientific observation and analysis regarding actual creatures, human and otherwise.

You’re seeing it, right? All three topics are about the soul with the serial numbers scrubbed off. I submit that describing human physiology and behavior in terms of special status, whether for some part or for some function or for a gestalt, lies in that exact issue.

Book recommendation: Sergio Della Sala’s Mind Myths

Links: Do we have a reptilian brain?, The left-brain / right-brain myth

Next: Who you are


3 thoughts on “Braaaiins

  1. How are Dr. “Burnt Toast” Penfield and his homunculus holding up?

    This diagram was featured in my 1987 Psych textbook:

    Is there a stable point with which a given set of sense receptors (say, my right pinky) sends converging signals? A point that might shift according to an individual’s development via neuroplasticity, but is in the same place for pretty much every human?

    Or is any one of the points to which Penfield’s labels points a construct assembled from a number of observations conducted over a diverse population of patients? Lungs may vary from person to person but they’re, you know, LUNGS and aren’t found under the bladder or upside down in this or that person.

    I remember being shown how easy it was to do reliably damage the brain in a particular area and get a prefrontal lobotomy done. But can a nick of a scalpel sever reception from the right pinky forever?

    All I have to go on is pop neuroplasticity hooked to the marketing of brain-training games, and functional MRI fans on the other.

    And years ago the semiotics textbooks cited early studies of aphasias that suggested a link between ways of relating words (metaphor and metonymy) and brain architecture. Has that been put to pasture too?


    • Hi, I wish some of my neuro colleagues could weigh in here for the latest.

      As I understand it, the homunculus diagram concerns sensory input and may have more to do with the number of receptors on the actual sensory organ than with the brain architecture. I don’t know whether or how much the left/right distinction is valid, but if it is, that doesn’t have much to do with the cognitive processing that the left-right brain myth is about.

      I’ll be posting about lobotomies soon. I’ll say here that it’s plain butchery with the precision of a pickaxe, and its effects are incredibly variable.

      One of the best brain-and-behavior researchers I know – and that’s saying something – refers to the lesion-based mapping of brain-bits to body organs as “twentieth-century phrenology.” It’s been established since the 80s that ruining a bit of the brain and then looking for what the organism does badly is not a valid technique. Typically you’re interfering with a regulatory area that affects tons of things and inadvertently cherry-picking the one you’re interested in.


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