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The Triune Brain

In a previous post, I brought up the question of why so many people believe off-the-wall things — things a rational mind would reject as being wrong-headed at best, loony tunes at worst.

I’m referring to people who believe in Bigfoot, or UFOs, or the Bermuda Triangle. Or people who think the UN is poised to send in black helicopters to take away their guns — as if the UN were competent enough to conceive a plot.

The fact is, folks out there believe things and reach conclusions that leave you wondering how they got that way.

I was tempted to wonder if more people than we realize simply have a reasoning disorder, but then a more plausible explanation surfaced.

New research suggests that the answer may be genetic. Our thinking may be influenced, to a degree not yet determined, by our genetic makeup.

Not all brains are “wired” the same. The variations, encoded in unique ways in each individual set of gray matter, help guide the conclusions we reach and the beliefs we hold.

Further, the research suggests that our reasoning patterns are not that difficult to predict.

This insight (or, more correctly, this theory) comes from research into a subject that gets more blood boiling than anything except a soccer match: political viewpoints.

To appreciate the research of which I speak, it helps to understand a bit about the overall structure and operation of the human brain. A good summary is the “triune brain” theory of the late neuroscientist Paul MacLean, Chief of the Laboratory of Brain Evolution and Behavior at the National Institute of Mental Health.

According to MacLean, the human brain evolved in three stages, and in effect, we have three interconnected brains inside our heads.

The first brain to develop was the primitive “reptilian brain” — the brain stem and related parts. This controls automatic body functions (breathing, circulation, digestion) and instinctive survival behaviors (hunger, reproduction, fight-or-flight).

The reptilian brain is all about physical survival. The instincts of aggression and territorial defense reside here. It is fear-driven and steps in when you perceive a threat.

Wrapped around the reptilian brain is the second brain to develop: the limbic or “mammalian brain” — so named because it emerged in the first mammals. This is the part of the brain that governs emotion, memory, and learning to make judgments that don‘t get you eaten.

The mammalian brain governs family ties, our behavior in groups, love/bonding, and feelings of empathy. This part of the brain evaluates daily experiences and classifies them as agreeable and disagreeable, so we know how to react when we next encounter them.

Wrapped around brain two is our third and most advanced brain, the “neocortex.” This is the seat of our higher functions — the center of awareness, abstract reasoning, problem-solving, and language.

As a bona fide human, you have a brain that is 75-80 percent neocortex. This is what makes you self-aware, curious about stuff, and capable of scratching an intellectual itch.

So — we have three brains up there which evolved in order. The three are intricately connected, but are capable of reacting independently and automatically.

Hold those thoughts until my next post, when I turn to the new research about how the internal wiring of our brain(s) affects our mental processes and opinions.