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

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.

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.

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.

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.

Image credit: Michal Hustaty

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Read this: This Is the Scientific Explanation for Why Introverts Like Being Alone

  • This is a very informative! Thanks for sharing!

  • I didn’t knew these things! I’m an introvert and I tend to over-analyze everything, but it’s the first time I hear about the dopamine connection. 🙂

  • Jules

    Who is the artist you got the cover photo from on Deviant Art? I really like it and would like to know who this person is.

  • Vee

    Very interesting! But I wouldn’t “blame it on my brain” because that implies I’m not comfortable with who I am. I definitely am.

  • Vee

    Oh, and I can relate to your bio about feeling the life sucked out of you in a 9-5 job!

  • cc

    interesting facts. but i don’t like the way its written like “we introvers, us introvers blah…” cuz it sounds biased…

    • GG

      Agreed! Also, it puts introverts into an unnecessary box. There are many levels of introverts, even some that balance well between an introvert and an extrovert.

  • Now I know why I become like this. Happy to be an introvert.

  • Cec

    Very interesting. I love learning about introverts as an extrovert. It seems as though there are many articles trying to explain being an introvert and how they were always misunderstood and how the world was not designed for them. As an extrovert, I always felt that school was never designed for me. It seemed that the children that were quiet were favored. As a parent of two extroverts and an introvert, I always preach that we need to be patient with both personality. Introverts and extroverts both need to be taught coping skills to survive difficult situations. It takes both type for the world to go round!

  • This is fascinating, thank you!

  • i now know that i am an introvert. i do over think things and am quite uncomfortable around a lot of people, and do feel like the ghost in the background. this article was very informative. thank you

  • Now I know why I need more time to make decisions. Your blog is so nice. It’s very informative.

  • Sarah Goodman

    Extroverts seem to be super-organisms, i.e. they are loud and talkative because they can’t think for themselves. Nothing against them, just a fact.

    • radiya

      Being an extrovert does not mean that they are not smart;Its a personality type that a person portrays the most, not something that determines how intelligent you are because being an introvert or extrovert doesn’t represents you being smart. This is coming from an introvert btw.

  • S. Quarfiti

    The article you cite has nothing to do with what you’re talking about … namely: “Dysregulated affect and impaired social cognition co-occur within disorders marked by abnormalities of the amygdala and mPFC [e.g., major depressive disorder (MDD)] (Curran et al., 1993; Drevets et al., 1997; Hajek et al., 2008; Mayberg, 1997; Price and Drevets, 2010; Savitz and Drevets, 2009b). A leading hypothesis is that variation in amygdala–mPFC circuitry, present within the general population, sets the stage for illness onset through its influence on both affective and social traits (Mayberg, 1997; Price and Drevets, 2010).”

    You are misleading your readers with these claims. Dishonest.

  • erik sudderen

    i am confused