Introverts’ and Extroverts’ Brains Really Are Different, According to Science

differences between introverts' and extroverts' brains

You’re not imagining it. That extrovert who seems so different from you? It’s because his brain is different.

Introverts Are Sensitive to Dopamine

Why do extroverts like action, but introverts like calm?

It has to do with two powerful chemicals found in our brains — dopamine and acetylcholine, “jolt juices” that hugely impact our behavior.

Dopamine gives us immediate, intense zaps of happiness when we act quickly, take risks, and seek novelty. Acetylcholine, on the other hand, also rewards us, but its effects are more subtle — it makes us feel relaxed, alert, and content.

Extroverts are less sensitive to dopamine, so they need more of it to feel happy. The more they talk, move, and seek new faces, the more they feel dopamine’s pleasant effects.

But we introverts are sensitive to dopamine, so too much of it makes us feel overstimulated and anxious, writes Dr. Marti Olsen Laney in her book, The Introvert Advantage: How to Thrive in an Extrovert World.

However, when we read, concentrate, or use our minds in any way, we feel good because our brains release acetylcholine. Extroverts, on the other hand, hardly register acetylcholine’s gentle happiness bump.

From "The introvert brain explained"
From “The introvert brain explained”

Introverts Prefer a Different Side of Their Nervous System

Everyone’s nervous system has two sides — the sympathetic side, which triggers the “fight, fright, or flight” response, and the parasympathetic side, which is responsible for “rest and digest” mode.

Think of the sympathetic side as hitting the gas pedal and the parasympathetic side as slamming on the brakes.

When your sympathetic system is activated, your body gears up for action. Adrenaline is released, glucose energizes muscles, and oxygen increases. Areas of your brain that control thinking are turned off, although dopamine increases alertness in the back of your brain.

But when you use the parasympathetic side, your muscles relax, energy is stored, and food is metabolized. Acetylcholine increases blood flow and alertness in the front of your brain.

Of course, extroverts and introverts use both sides at different times. But which side do we introverts prefer? You’ve probably already guessed: according to Dr. Laney, the parasympathetic side, which slows us down and calms us.

Introverts Use the Long Acetylcholine Pathway

Ever wonder why, as an introvert, you overthink?

It has to do with how we process stimuli in a different way than extroverts do.

When information from the outside world — like someone’s voice or images on a computer screen — enters an extrovert’s brain, it travels a shorter pathway, passing through areas of the brain where taste, touch, sight, and sound are processed.

From "The introvert brain explained"
From “The introvert brain explained”

But for us introverts, the pathway is much longer. Stimulation travels through many areas of the brain, including:

  • The right front insular, which is an area associated with empathy, self-reflection, and emotional meaning. This is also the area of the brain that notices any errors.
  • Broca’s area, which plans speech and activates self-talk.
  • The right and left front lobes, which select, plan, and choose ideas or actions. These areas also develop expectations and evaluate outcomes.
  • The left hippocampus, which stamps things as “personal” and stores long-term memories.
From "The introvert brain explained"
From “The introvert brain explained”

This means we process information more thoroughly and deeply. No wonder it sometimes takes us longer to speak, react, or make decisions!

Introverts Have More Gray Matter

study published in the Journal of Neuroscience found that introverts had larger, thicker gray matter in their prefrontal cortex, which is the area of the brain that is associated with abstract thought and decision-making. Extroverts had thinner gray matter in that same area. This suggests that we devote more neural resources to abstract thought, while extroverts tend to live in the moment.

What This Means

It means that as an introvert, you were probably born this way — although, of course, your background and experiences play a role in shaping you, too.

It doesn’t mean that you’ll never enjoy a party or seek new experiences, or that an extrovert will never sit still and read a book — we still get to choose what we do.

And of course, “introversion and extroversion are not black and white. No one is completely one way or another — we all must function at times on either side of the continuum,” Dr. Laney reminds us in her book, The Hidden Gifts of the Introverted Child.

That extrovert? Give him a break. It’s his brain.

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Jenn Granneman is the founder of and the author of The Secret Lives of Introverts: Inside Our Hidden World. She also cohosts The Introvert, Dear Podcast and blogs for Psychology Today. For most of her life, Jenn felt weird, different, and out of place because of her quiet ways. She writes about introversion because she doesn’t want other introverts to feel the way she did.