There is No "Primitive" Part of the Brain

Was watching some old interview about "emotional intelligence" (itself a fraught term, but that's for another day) last night, when the interviewee (Daniel Goleman) calmly stated that emotional intelligence comes from your "primitive brain" that "arose earlier in evolution".  ARGHGHSAGHGHGH

(Click for time of offending remark)


This idea of there being a "primitive" brain crops up all over the place, and from reputable sources:

"This means that areas traditionally considered to be more primitive were just as important during our evolution." (Professor Robert Barton, Durham University, said that).  N.B. please see this comment from Dr. Barton:  As one of the people quoted, I am going to cry foul! I do completely agree with your thesis, and that was the point of my comment about "areas TRADITIONALLY ASSUMED to be primitive". I have been on a mission to repudiate the "ice cream scoop" idea of brain evolution, and have shown that cortex and subcortical structures co-evolved. So keep up the good work, but please don't attack those who agree! Robert Barton  But note that despite his good intentions, his quote eventually led to this article - the number one hit on google for "primitive brain" - to be written.  The phrase has power!

"They suggest that new learning isn't simply the smarter bits of our brain such as the cortex 'figuring things out.' Instead, we should think of learning as interaction between our primitive brain structures and our more advanced cortex. In other words, primitive brain structures might be the engine driving even our most advanced high-level, intelligent learning abilities" (Picower Professor of Neuroscience Earl Miller, MIT, said that).

"It's like adding scoops to an ice cream cone.  So if you imagine the lizard brain as a single-scoop ice cream cone, the way you make a mouse brain out of a lizard brain isn't to throw the cone and the first scoop away and start over and make a banana split — rather, it's to put a second scoop on top of the first scoop." (Professor David Linden, Johns Hopkins, said that).

Now let me explain why this is all complete BS.

First, semantics.  What is "primitive"?  How do you measure a tissue's "primitivity"?  In the common usage of the word, primitive means simple, especially in the context of a task, idea, structure, way of life, etc that was employed a long time ago.  Cavemen were more primitive than us, for example.  Unfortunately, this means that "primitive" is a word that refers to things both "ancient" AND "simple".  Which, as we'll see, is a big problem when you start applying it to mean only one of those things as occurs with the "primitive brain" meme.

Second, what are people actually talking about when they say "primitive brain"?  This is confused as well, but in general the thought is structured like this:

Most primitive - brain stem, pons, cerebellum.  (The hindbrain, basically).

Also primitive - the limbic system where "limbic" means "border, edge".  This includes the hippocampus, amygdala, parts of the thalamus (who knows why), some of cortex, and some other bits.  It's supposed to do "emotion" and this is what Daniel Goleman is referring to when he talks about the "primitive brain".  Really though it's just a lumping together of all the structures right near the inner border of cortex, because why not lump it all together?

Gloriously advanced - the mighty cortex (you know, the wrinkly part on the outside).

Third, why do people say that these particular brain structures are "primitive"?  The idea is that evolutionarily, one came after the other.  As in, the first vertebrate just had a brain stem.  Then it evolved more stuff after that.  Then as things kept evolving, more and more stuff got added on.  This is the "ice cream cone" model that David Linden espouses.  It's also incredibly stupid (or at least misleading).  Let's break it down.

Evolution did not happen like this:

Evolution did happen like this:

                                   

 I hope everyone pretty much understands the concept of a phylogeny and the fact that every vertebrate came from one common ancestor.  Yes, the common ancestor was a kind of fish.  No, today's fish aren't the same as the common ancestor.  They evolved from it just like everyone else, although "rates" of evolutionary phenomena like mutation and drift can vary and that's beyond the scope of this post.

The point is that the "primitive" brain meme is born in the idea that the brain components fish, lizards, mice, and humans share in common must be evolutionarily ancient and were likely shared in common by the common ancestor.  So, homologous structures across the phylogeny indicate "ancientness".  And "ancientness" = "primitive".  (Except it doesn't, but more on that in a second).

And since we all share structures that resemble the brain stem, voilà!  That's the most primitive part of the brain.  Here's where things go astray.

First, we don't just share the brain stem with all animals.  Here's the real "ice cream cone" of the brain:

 

And when I say "the" brain, I should say "all vertebrate brains".  Every fish, bird (including reptiles), amphibian, and mammal has a brain that starts out looking like the pictures above.  Each colored bump (or "scoop of ice cream") represents a region of the brain very early on in development, when the whole nervous system is basically a simple tube.  Each bump goes on to expand to varying sizes into varying kind of structures and yadda yadda depending on the species.  The point, though, is that all vertebrates have a forebrain, a midbrain, and a hindbrain.  And the hindbrain, by the way, is the "primitive" brain stem.  But clearly, humans, fish, lizards, and mice all evolved from a common ancestor that had all brain regions, not just the hindbrain.

This is why David Linden's ice cream analogy is so dumb.  He's implying that first you start with one scoop, the hindbrain, then add on another (the midbrain), and finally one more (the forebrain).  Or at least he led NPR to believe that's the case:

When mammals like mice came along, the lizard brain didn't go away. It simply became the brain stem, which is perched on top of the spine, Linden says.  Then evolution slapped more brain on top of the brain stem.

 

But that's not what happened at all.  All the scoops were there to begin with.  Then as adaptation took its course, different scoops got bigger or smaller or just different as you began comparing across the entire phylogeny.  Yes, humans have an enormous cortex and lizards don't.  And yes, lizards simply evolved a different-looking kind of forebrain.  That's all.

Second, homology does NOT imply "ancientness".  Even if the hindbrain looks pretty similar across the vertebrate phylogeny as it exists today, that doesn't make it "ancient".  The hindbrain has been evolving just like the midbrain and the forebrain.  Maybe it's not been changing as much, but it's still been changing.

This leads me to why the "primitive" notion is so misleading, and should be avoided:

(1) Calling a part of the brain "primitive" suggests what David Linden articulated: that brain evolution happened like stacking scoops of ice cream.  It implies that our brain stem is no different than that of a lizard, or of a mouse, or of a fish.  Yet despite their vast similarities, they are clearly not the same.  You can't plug a human forebrain into a lizard hindbrain and expect the thing to work.  The hindbrain of humans HAD to adapt to having an enormous forebrain.  There's something seductive in the idea that inside all of us is a primal being, a "reptilian brain".  There isn't.  It's a human brain, top to bottom.

(2) Calling brain parts "primitive" because they are shared across phylogeny is often used to justify how amazing our human cortex is.  Look at what makes us us!  We're so great!  Well, I guess.  But we are just one little excursion among many that evolution has produced.  The lizard brain is adapated for what lizards need to do.  The fish brain is adapted for what fish need to do.  They don't have "primitive" brains.  They have highly adapted brains, just like any other vertebrate.

(3) Simply using the word "primitive" makes the casual reader think of cavemen.  It just does.  And that's even more ridiculous, because ancient Homo sapiens were still Homo sapiens.  Read what this poor misinformed blogger has written:

So, let me explain the Primitive brain in simple terms. We have an Intellectual (rational) part of the brain and a Primitive (emotional) part of the brain. In the picture above, the Primitive brain is around the Hippocampus and Hypothalamus areas. In some texts, it has also been called the Limbic System.

The subconscious Primitive part has been there ever since we were cavemen and cavewomen, and houses our fight/flight/freeze response (in the amygdala in between the Hippocampus and the Hypothalamus). Its function is to ensure our survival.

AHHHHHHHHHHHHHHH.  You see?  You see??????

 (4) There is not just a "primitive, emotional brain" and a "complex, intellectual brain".  That is so.... wrong.  Factually wrong.  Yet people like Daniel Goleman sell books about emotional intelligence claiming that people need to develop their "emotional brain" and then bloggers like Carrie (above) start internalizing and spreading the misinformation.  Folks.  Let me be clear.  You have ONE brain.  One.  It has many parts, which is to say that humans looking at brains have found ways to subdivide them into various areas and regions and structures and whatnot.  Regardless of all that, the whole damn thing works together.  It's one big circuit that does emotion, rationality, sensation, movement, the whole shebang.  There isn't a simplistic "emotion" part and an "intellectual" part.  The cortex is involved in emotions and feelings.  The basal ganglia are involved in cognition.  In fact, the whole idea of splitting emotion and reason into two separate camps is fraught, as emotion turns out to be critical in reasoning tasks like decision-making.

(5) The "primitiveness" of lizard brains is vastly overstated.  Things like this get written about the "primitive brain":

A lizard brain is about survival — it controls heart rate and breathing, and processes information from the eyes and ears and mouth.

This implies, to the casual reader, that lizards are just sitting around breathing.  Maybe there's some "survival instinct" in there: look out for that big hawk!  Yeah, okay.  But guess what?  Lizards gotta do other stuff too.  They have to reproduce, find food, navigate their environment, learn, remember, make choices, etc.  They aren't just breathing and instinct machines.  And because they aren't, that means their brains aren't just doing that either.  And why is it always lizards and reptiles?  You'd think fish would get picked on more.

(6) "Primitive" in the context of a brain part primarily means "ancient".  But the word "primitive", as we already saw, connotes simplicity.  This leaves laypeople with many misconceptions.  First, that the brain stem, or the "emotional brain", or whatever is simple.  Or even that they're simpler.  Nope.  Not really.  Pretty much every part of the brain is complex.  Second, it reinforces, in the case of the "emotional brain", that emotions are beneath intellect.  They came first, they are older, they are simpler, they are the stupid part of your brain.  Again, just no.  You need emotions to survive just as you need your intellect to survive.  Fish need their emotions (an emotion, after all, is just a representation of bodily state imbued with a certain postive/negative valence) just like they need their reasoning abilities as well.

(7) People using "primitive" as scientists do it because it can sound cool and surprising.  Look at how Earl Miller framed it, from above:

"They suggest that new learning isn't simply the smarter bits of our brain such as the cortex 'figuring things out.' Instead, we should think of learning as interaction between our primitive brain structures and our more advanced cortex. In other words, primitive brain structures might be the engine driving even our most advanced high-level, intelligent learning abilities"

Look at that result!  A primitive thing did something advanced!  The forgotten thing is important!  Or maybe - this is going to sound crazy - the whole system evolved together in order to support such essential tasks like learning.  There never was a primitive part or an advanced part, despite two areas or regions being labeled as such.  Every part of the human brain has been evolving for the same amount of time as every other part, and has been evolving to work as best as possible with each of those other parts.

(8) Finally, let's return to Daniel Goleman, who argues that "emotional intelligence" arises from the "primitive emotional brain".  Then he waxes on and on about the value of emotional intelligence, particularly as it relates to social abilities.  Ability to understand your own emotions.  Ability to perceive those of others.  Ability to interact well with others on the basis of understanding their emotions.  Et cetera.  That's all fine, but by saying this comes from an ancient, primitive, emotional brain might make people think that ancient vertebrates really had to know themselves, be able to read others, and interact socially.  But there's a whole lot of solitary, nonsocial vertebrate species out there folks, and they have brainstems and limbic systems too.

Okay folks.  Hopefully never again will you refer to a part of the brain as "primitive."  Some structures probably more closely resemble their homologous counterparts in the last common ancestor of vertebrates, but all the basic parts were there from the beginning.  And remember, evolution didn't happen just to make humans.  We aren't more advanced in an evolutionary sense than fish, lizards, or mice.  Each species is just adapted to the roles it finds itself in, and continues to adapt.  Our sense of being "advanced" comes purely from our own self-regard and anthropocentric tendencies. The human brain is not the best brain, nor is it the most advanced brain, because there's no scale on which to measure how good a brain is.  

To reiterate: we don't have primitive brain parts.  Your urges, desires, rages, and other feelings you think you shouldn't have can't be excused away to a "primitive" brain.  You are your brain - the whole thing.