Goodbye Lizard Brain
Only lizards have lizard brains. Why the Triune brain theory deserves a bad rap. And four good reasons why we should not use it in psychotherapy.
The lizard brain is the classic, original neurobollocks. It contends, in its various versions, that parts of our brain, a vestige of our evolutionary history, propels us into animal reactivity and the 'fight-or-flight' response. Portrayed as being at odds with the more 'modern' and 'human' parts of our brain, this unruly reptilian bit is generally seen as ‘bad’ and we are often given various 'neuroscience-based' advice on how to overcome its maladaptive tendencies.
Naively, however, I was under the impression that the lizard brain was a thing of the past. It belonged, or so I thought, together with other urban myths such as the alligators in the sewers and “we only use 10% of our brain”. Nobody believed it anymore and more sophisticated neuro-myths had taken its place.
But when I referred to it humorously in my writing, a number of people got back to me sounding genuinely surprised. Some even defended the idea vehemently. I realised the concept still had a solid footing in the neuroscience-curious psychotherapy community.
And that is when I knew: I would have to come face to face with the atavistic reptile residing in my skull for one final showdown.
And because they've done it so well, I could practically just quote verbatim the brilliantly titled paper "Your Brain Is Not an Onion With a Tiny Reptile Inside", which makes the point far better than I ever could. Additionally, in this piece, I combine voices of other neuroscientists who have taken on this important reptilian question.
The Essence of Lizard Brain: What Is It and What the Idea Really Intimates
The Lizard Brain Definition:
The consensus seems to be that the lizard brain is a lowly, primitive, and less-evolved part of our brain and one that we must combat and resist, as it gets us into trouble by leading us to make poor decisions and behave in ways that are unhelpful and uncharacteristic of our more evolved selves. It’s also seen as selfish and non-social.
However, the consensus is sometimes lacking as to which part of the brain is actually the lizard brain. Some proponents seem to think that it is the brain-stem. Others purport it is the amygdala. Some even equate operating from the lizard brain with operating from lower chakras. (For sure, science has lots of catching up to do).
The terms lizard brain and reptilian brain are used interchangeably here, presumably because lizards belong to the taxonomic group of reptiles, along with crocodiles and snakes. Thank God the trend hasn’t extended to talking about the snake brain or crocodile brain. There is something powerfully atavistic about evoking reptiles that captivates our imagination. Think Alien movies or the popular reptilian conspiracy.
How Did the Lizard Brain Come to Being: The Triune Brain Theory
The idea that the human brain possesses a lowly component inherited from our reptilian or other ancestors is quite an old one, dating back to the late 19th century. However, this view gained real traction in the psychotherapy world through the advent of the Triune Brain Theory.
This idea of parts of the brain stacked on the top of each other in order to create mental and behavioural complexity is as illustrated by the following passage from the book Man and His Animal Brains by Paul MacLean, the originator of the Triune Brain (as cited here):
"man, it appears, has inherited essentially three brains. Frugal Nature in developing her paragon threw nothing away. The oldest of his brains is basically reptilian; the second has been inherited from lower mammals; and the third and newest brain is a late mammalian development which reaches a pinnacle in man and gives him his unique power of symbolic language."
Frugal Nature notwithstanding, it hardly sounds like something we should take as scientific truth today, right?
The Triune Brain is an example of the ladder of nature (or scala naturae, in Latin) theory. It belongs to a long lineage of theories woven into Western religion, philosophy, and even early science, including pre-modern neuroscience. These theories suggest a progressive development of beings, from inanimate objects to increasingly complex creatures, culminating in the pinnacle of creation: the human and ultimately, the divine.
(A good analysis of this cultural phenomenon starting as far as Aristotle, in relation to neuroscience, can be found in the book "The Entangled Brain" by Luiz Pessoa)
According to this view, the three brain layers have distinct functions, arranged in order from the most primitive to the most sophisticated, uniquely human capacities. The reptilian layer governs reflexes; the mammalian layer is responsible for emotions; and the newest layer, the neocortex, handles cognition, language, and the ability to put the brakes on instinctive drives and reflexive behaviours.
So What Is Wrong With This View?
It is worth noting that this isn’t an outdated theory, as for a theory to be outdated, it first needs to have been widely accepted. The Triune Brain Theory seems to never have been embraced as an accurate reflection of the organisation of the human brain. And yet, somehow, it has become entrenched in the realms of psychology, self-improvement, and psychotherapy.
So what is so wrong about it?
The Brain Evolution Is Not a Linear Process That Adds Layers
For starters, this view assumes that organisms' brains evolve in complexity by simply adding new layers on top of existing ones. It also places humans at the pinnacle of evolution.
Both assumptions are wrong.
The more accurate view is that all vertebrates share a common ancestral brain structure composed of three main regions: the hindbrain, the midbrain, and the forebrain. As different species evolved, these regions evolved too sometimes becoming more complex, but not always. And when it comes to complexity, humans are not the only animals with remarkably sophisticated brains.
The neocortex, for instance, is not a uniquely human or even primate invention. Other mammals' brains have cortices and not only limbic structures.
Even the prefrontal cortex is not exclusive to humans. In fact, in rats, the prefrontal cortex plays a role in decision-making and delayed gratification. These ideas are elegantly explored here, if you are interested in exploring this question further.
To put it simply, in the words of neuroscientist Lisa Feldman Barrett: “Only lizards have the lizard brain”.
As for the idea of the human brain as the pinnacle of evolution our thinking has historically been deeply anthropocentric, often shaped by the complex relationship between God and man. That is of course no longer a framework for understanding how the brain is structured or how it works.
And really, you don’t need to be an evolutionary biologist to understand this. Ricky explains it quite beautifully in his sketch on evolution.
Reptiles Are Not Evolutionary Ancestors of Humans
Secondly, to 'inherit' the lizard brain from our ancestors we would have to have an ancestor who is a reptile, right? But reptiles and lizards were never human ancestors - we don't belong to the same branch of the evolutionary tree. Therefore, it does not make sense to talk about humans inheriting the lizard brain from our reptilian ancestors. As simple as.
The Limbic System Is Not the Neural Correlate of Emotions
One important corollary of the Triune Brain Theory, particularly in the context of psychotherapy, is the idea that the limbic system is an evolutionary, mammalian inheritance and the supposed seat of emotions.
But for quite some time now, we have known that the stark dichotomy between cognition and emotion simply doesn't hold. The two are deeply intertwined, and cognition is better understood as a phenomenon that encompasses both thinking and feeling.
Lisa Feldman Barrett, who studies emotion, makes a compelling case for why the limbic system cannot be considered the exclusive seat of emotions. Emotional processes involve both cortical and subcortical areas. Moreover, brain regions traditionally labeled as part of the "limbic system" are involved in a wide range of functions including decision-making, memory, attention, perception, and even consciousness. Perhaps most striking are clinical examples of patients with damage to key limbic structures who nevertheless continue to experience emotional responses offering a powerful counterpoint to the ‘limbic system’ view.
But Even If It Is Not True, Could It Be a Useful Approximation in Psychotherapy?
I can already hear the question bubbling up: "Alright, alright but isn’t it still a useful approximation? A simplified account that helps convey complex brain ideas to therapists and clients without scaring them off?"
My response is a question back to you:
What are the actual benefits of using this idea either in your work with clients or in your own clinical thinking that aren’t also inaccurate or misleading?
Or more to the point: what is the value in telling a client that we have an archaic part of the brain called the “lizard brain” that we must fight against using our “higher” mental faculties from the newer parts of the brain when that simply isn’t true?
I co-wrote a whole post on this kind of thing, particularly in the context of psychotherapy and neuroscience integration. It’s called Schrödinger’s Cat of Psychotherapy. The gist is this: if we want to bring neuroscience into psychotherapy, then let’s actually bring neuroscience not myths. To be sure, simplification might be necessary but it has to be done in a way that’s consistent with (ideally up-to-date) research findings, not in direct contradiction to them. It's just common sense, isn't it?
Ultimately, the choice is yours, but I am going to give you four solid reasons why "lizard brain" language is just not a good idea:
Unsupported by Science: Modern neuroscience does not support the existence of a brain structure inherited from lizards, nor does it support the idea that brains evolve by simply adding newer layers on top of more primitive parts.
Supports the 'Ladder of Nature' Narrative: It reinforces the outdated ladder of nature concept and is mistakenly anthropocentric by placing the human brain at the apex of brain evolution.
Misinterprets and Oversimplifies Cognition and Emotion: It wrongly downgrades emotions to a "lower" evolutionary status, ignoring the fact that cognition and emotion are inextricably linked. There is no cognition without emotion, and no emotion without cognition, especially in humans.
Last but Not Least: You don’t want to be this guy 😆👇
That might just be the end of the road for the lizard brain. Goodbye 🦎🧠👋.
Very good! And btw, lizards are just as evolved as humans are (by definition, given they are the product of the same process that gave rise to us!)
Agreed on the phylogenetic issue with the so-called ‘lizard brain’, but the general point of the brainstem and subcortical regions being phylogenetically older still holds. I also appreciate the nuance that Barrett brings into the conversation of emotion, but I’d suggest that she fails to sufficiently address the role of affect—the raw substrate of emotion—as having a neural correlate in the brainstem. Affect and emotion are not the same thing, but they tend to be treated as though they were. The cortex plays an important role in the formation of emotions, but emotion is downstream of affective consciousness. MacLean’s Triune Brain and other similar models are best conceptualized as a loose heuristic rather than systems with strict anatomical boundaries. And I'd also add that nothing in those models requires the instinctive substrate to be ‘bad’ or maladaptive.