You Do Not Have a Lizard Brain (But Your Brain Is Like a Lizard’s)

It’s our last week of myth-busting blogs, and we’re taking on a big one. It emerged more than 65 years ago. Despite almost immediately being called into question and later outright disproved, it persists today. And I don’t just mean that it gets thrown around on sales and marketing blogs (although it does)—it still appears in 86 percent of introductory psychology textbooks.

I’m talking about the lizard brain. That ancient vestige inside all of us that doesn’t respond to facts or logic. Did you snap at your partner for no reason? Lizard brain. Do you keep buying doughnuts every morning even though you know you shouldn’t? Lizard brain. Feel like punching someone in the throat? Lizard brain.

There’s just one problem—you don’t have a lizard brain.

A RIDDLE, WRAPPED IN A MYSTERY, INSIDE AN ENIGMA…BUT NO LIZARDS

This notion of the lizard brain is part of the triune brain theory. This explanation of brain evolution posits that our brains developed, and continue to function, in three successive layers. The center layer is the most primitive portion, the so-called “lizard brain,” which functions on instinct only. This more primitive portion was then enveloped by a more sophisticated (but still very old) layer, the limbic system, which controls emotion.

Finally, these two brain layers were surrounded by the most sophisticated layer, the neocortex, possessed only by humans and possibly apes. The neocortex is what gives us rational thought. You must admit, it sounds cool. It’s like the turducken theory of brain evolution. Or like your brain is a not-so-attractive Russian nesting doll. The outer, largest portion, being the most advanced—the tiniest doll only capable of basic, instinctual behavior.

As humans, we like to have neat and tidy explanations. We love to categorize. Give me a quiz and put me in a category that explains why I act the way I do. We especially enjoy tidy explanations that make us out to be special compared to other animals. Plus, this particular theory gives us an excuse for when we do something wrong. It wasn’t our fault. Our primitive brain took over. Like most things in life, however, the real answer is more complicated. Evolution is messy, non-linear, and doesn’t have neat clean layers.

BIRTH OF THE LIZARD BRAIN

The triune theory was proposed by neuroscientist Paul Maclean. He wrote about the “lizard brain” and the triune concept back in 1957 and continued writing about it into the 1990s. MacLean was a physician as well as a neuroscientist. He worked at Yale Medical School and the National Institute of Mental Health. Despite his theory being incorrect, he made great contributions to science through his research and advanced the field of neuroscience.

The information available on him falls into two distinct camps—it either covers the facts that he made many contributions and developed the triune brain theory (and does not mention that the theory is incorrect), or it makes a point of clarifying that, while compelling, the triune brain theory is incorrect, and that perhaps MacLean’s practices and methods were a little out there.

In a Yale School of Medicine article, he’s described as “eccentric.” In the same article, one of MacLean’s fellow researchers at Yale describes him as irreverent and uninhibited. He then recounts a story of MacLean walking through a room and feeling the scalps of visiting scientists to see if they had a skull protuberance that MacLean thought was an important factor in the evolution of human intelligence. Can we please just stop there for a moment? Describing a man who goes around feeling other people’s skulls to judge their intelligence as “uninhibited” is like when I describe my off-the-rails nine-year-old as “spirited.”

There are also some descriptions of MacLean’s research that make it sound less-than substantial. A neuroscientist at UCLA describes the study that led to the triune theory as MacLean excising part of a monkey’s brain (which he reportedly called the “reptilian complex” because it looked like the tissue that makes up reptile brains) and observing that the monkey stopped its aggressive gesturing. This experiment and “other loose observations” lead to the triune theory.

Whether or not his methods were entirely solid, his theory took hold. The reason the non-scientific community learned about it is mostly due to Carl Sagan’s book, The Dragons of Eden, which was published in 1977 and won him a Pulitzer in 1978. The book examined the evolution of the human brain and brought the triune brain theory to the masses.

YOU ARE SPECIAL. AND SO ARE SQUIRRELS.

What’s curious is that the scientific community disproved the triune brain theory just as Sagan’s book was gaining popularity. One disadvantage MacLean had was the tools at his disposal in the 1950s. All he could use was a microscope. Advances in molecular genetics have proven the triune theory to be false.

First, MacLean’s ideas about how the brain evolved were completely wrong. Brain evolution (and really any evolution) does not happen in an additive manner. Completely new structures don’t get added to older structures. Instead, biological structures are just modified versions of older structures. Vertebrate brains are all made of the same ingredients. There aren’t old parts and new parts.

Second, and probably most upsetting for humans, is that our brains are not fundamentally different than a lizard’s. Wait, it gets worse. Our brains are not even fundamentally that different than those of fish. It turns out that all vertebrates have at least analogues of a cortex, and every mammal (not just humans and apes) has a neocortex. This brain layer you thought made you special? Squirrels have it.

In fact, according to distinguished professor of psychology at Northeastern University Lisa Feldman Barrett, the whole idea that different parts of the brain have specific psychological jobs is false. Our brains are huge networks of neurons, most with multiple jobs. Furthermore, lizard brains, mouse brains, human brains—they are all made from the same types of neurons. Their number and arrangement differ between species, but not their basic makeup.

Even the MRI studies that show specific feelings activating specific portions of the brain are somewhat misleading. Those scans are expensive, and most studies only do enough to show the strongest brain activity. There is a lot of, though not as strong, psychologically and biologically meaningful activity going on in other parts of the brain. Our brain isn’t made of pieces of a puzzle that fit neatly together. It’s a single entity, and the parts don’t function separately.

BECAUSE SCIENCE

Fine. You don’t have a tiny lizard brain inside your head controlling your most basic, instinctual behaviors. Is it really a big deal that we keep perpetuating this myth? Who does it hurt?

Thinking about the brain as a 3-layer series of ever-more-complicated structures can impact current neurobiological research. It leads researchers to ask the wrong questions. As Joseph Ciserio et al. write in their article “Your Brain Is Not an Onion with a Tiny Reptile Inside,” perpetuating myths such as the lizard brain can impact how scientists look for new answers. “The question of willpower is not ‘Why do people act sometimes like hedonic animals and sometimes like rational humans?’” they write, “but instead, ‘What are the general principles by which animals make decisions about opportunity costs?’”

Plus, the great thing about scientific research is that there is a method for testing theories and learning more. We develop better tools and uncover new information and change what we think. If we didn’t shift our thinking based on new information, it wouldn’t be science. It would be politics.

Maybe that was a cheap shot at politics. Maybe there are some of you that want to punch me in the throat right now. Just know that if you do, you can’t blame your inner lizard.

We all have instinctual reactions that we often must fight in sales. When someone hands us an objection, it’s natural for our rate of speech to increase. When there is a long pause after we ask a question, it’s tempting to fill the silence ourselves.

Your (completely human) instincts on a deal may be right or wrong. Don’t let that color your judgment on what to do next. That’s why it’s critical to use a highly honed and practiced sales process. Dig in using a tested framework like DRIVE to figure out what’s really going on. Your professional success should not be dependent on instinct—lizard, human, or otherwise.

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