The Scientific Evidence for Introversion and Extroversion

- By a friend of the CT admins -

What do Johnny Depp, Friedrich Nietzsche, Hans Christian Andersen and Richard Nixon have in common? None of them could fill a position for which the employer sought an “extrovert and dynamic” staffer. Why? Because all of the above belong in a psychological category which scientists call introverts.

Introvert. The word is often associated with something odd and negative. The ingrained cultural examples are found, for example, in the standard characterization of Beethoven as “brusque and introverted”; an unpleasant fellow at whom one would not even look the wrong way.

Introvert. Antisocial. Uninterested. Unapproachable. A real party pooper. That is how introverts are usually characterized in a world which considers extroversion as the one and only healthy stage. Introversion is something the introverted should apologize for and not speak too loudly about.

But what if introversion is not pathological? What if introverts are not inhibited in the way we usually describe them? What if introversion is more than a confused teenager’s awkward attempts to cope with his Weltschmerz? What if it isn’t a personal decision that testifies to selfishness, but a naturally occurring neurological configuration, complete with both advantages and disadvantages? That assertion is now legal tender in the neuroscientific field.

Brain researchers have identified a number of physiological differences in the brain that separates extroverts from introverts. Specifically, one difference is found in the thalamus area and another in the frontal lobes. These are areas of the brain involved in memory, planning and problem solving.

By studying the behavior of introverted and extroverted people, we can observe how these physiological differences are expressed. Research shows that people who meet the criteria for introversion are less able to cope with distractions such as background chatter, noise and passive, white noise while working on problems. When exposed to distracting and turbulent surroundings, introverts are simply slower and less able to solve the given assignments than extroverts are.

The open-plan office is a living nightmare for any introvert as it actively hinders concentration and furthers stress by going completely against the introvert’s preferred working conditions, namely peace, tranquillity and predictability.

The Evidence
To verify the theory of introversion/extroversion, researchers also did the opposite experiment: They placed a number of test subjects in a completely white room with no windows or pictures on the walls. Here they told the test subjects to remain quiet. And while the introverts followed the instructions and did indeed remain quiet, it did not take long for the extroverts before they began to whistle or drum the walls with their fingers. The most radically extroverted of the test subjects even began to walk in circles, despite the researchers’ unambiguous instructions to the contrary.

Looking over the evidence, a recurring feature across various research results is the introvert’s increased response to external stimuli: Introverts react more strongly to pain, smell and taste – they even produce a larger amount of saliva when a drop of lemon juice is placed on their tongues, and when measuring various physiological parameters such as brain waves and blood flow in the brain, one can see that there is generally increased activity in the introverted brain.

One theory goes like this: As the introverts have a naturally high level of activity in the anterior part of the brain, they are therefore not in need of significant extraneous stimuli. You could say that introverts are by nature is more or less chronically preoccupied by their own cognitive processes. Extroverts, by contrast, live in a form of chronic “activity deficit” and must therefore seek external stimuli to maintain a certain level of activity and function in their brains. – You can say that extroverts need stronger influences before the brain understands the message (e.g. more lemon juice to produce the same response), and so a room without stimulants provokes the extrovert to produce his own entertainment.

Dopamine and the Brain

The higher activity in the brains of introverts is thought to be caused by dopamine, and it is believed that the introvert brains contains a greater quantity of dopamine. – And that the level of dopamine determines the degree of introspection or extroversion. Comparing this with the existing genetic studies of introverted and extroverted, it turns out that there are in fact structural differences between the dopamine receptors of introverts and extroverts.

Introverts thus find themselves in constant danger of being over-stimulated or “flooded” by dopamine. Introverts therefore exhibit certain empirical commonalities, however different their personalities may otherwise be.

Introverts hesitate before engaging in speech, and in contrast to extroverts they often have a need for a “familiarization process” before they can “find their feet” in unexpected situations or in an interaction with strangers. Introverts works best alone and undisturbed and when they have time to immerse themselves in their own thoughts and ideas. They communicate best one-on-one, and when they socialize, they often prefer small intimate companies rather than large parties.

Looking at the demographic breakdown, introversion is evenly split between men and women. However, when we can still can speak of a cultural hegemony in favour of the outgoing it is  undoubtedly because introverts are a minority in the population at large, specifically around 25-40% of the population qualify as introverts, varying from strongly introverted, to certain introverts who are so close to limit that in practice they might as well be extroverted, in the scientific jargon known as “ambiverts”.

Many introverts report that they experience their introversion as a handicap in a society where extroverts set the agenda: Because introverts may be soft-spoken and slow to adapt to new input, they are often overlooked in social situations, and the outcome of the introvert’s carefully used cognitive processes never enter into play, which is a shame because introverts are often able to tenaciously concentrate on a specific topic for long periods of time and therefore can be incredibly creative and original.

So don’t let yourself be fooled by the introverted, at times somewhat reserved people around you. There is a force inside them which harbours a rich and imaginative world, just waiting to be let out.

What does Johnny Depp, Friedrich Nietzsche, Stanley Kubrick and Richard Nixon have in common? None of them could fill a position for which the employer sought an “extrovert and dynamic# staffer. Why? Because all of the above persona belong in a psychological category which scientists call introverts.


Introvert. The word often associated with something odd and negative. The ingrained cultural examples are found, for example, in the standard characterization of Beethoven as “brusque and introverted”; an unpleasant fellow at whom one would not even look the wrong way.


Introvert. Anti-social.
Uninterested. Unapproachable. A real party pooper. That is how introverts are usually characterized in a world which considers extroversion as the one and only healthy stage. Introversion is something the introverted should apologize for, and would not speak too loudly about.


But what if introversion was not pathological? What if introverts were not inhibited in the way we is usually ascribe them? If introversion was more than a
confused teenager’s awkward attempts to cope with his Weltschmerz? What if it wasn’t a personal decision that testifies to selfishness, but a naturally occurring neurological configuration, complete with both advantages and disadvantages? That assertion is now legal tender in the neuroscientific field.


Brain researchers have identified a number of physiological differences in the brain that separates extroverts from introverts. Specifically, one difference is found in the thalamus area and another in the frontal lobes. These are areas of the brain involved with memory, planning and problem solving.


By studying the behavior of introverted and extroverted people, we can observe how these physiological differences are expressed. Research shows that people who meet the criteria for introversion are less able to cope with distractions such as background chatter, noise and passive, white noise, while working on problems. When exposed to distracting and turbulent surroundings, introverts are simply slower and less able to solve the given assignments than extroverts are.

The open plan office is a living nightmare for any introvert as it actively hinders concentration and furthers stress by going completely against the introvert’s preferred working conditions, namely peace, tranquillity and predictability.

The Evidence


To verify the theory of introversion/extroversion, researchers also the opposite experiment: They placed a number of test subjects in a completely white room with no windows or pictures on the walls. Here they told the test subjects to remain quiet. And while the introverts followed the instructions and did indeed remain quiet, it did not long for the extroverts before they began to whistle or drum the walls with their fingers. The most radically extroverted of the test subjects even began to walk in circles, despite the researchers’ unambiguous instructions to the contrary.


Looking over the evidence, a recurring feature across various research results is the introvert’s increased response to external stimuli: Introverts react more strongly to pain, smell and taste – they even produce a larger amount of saliva when a drop of lemon juice placed on their tongues, and when measuring various physiological parameters such as brain waves and blood flow in the brain, one can see that there is generally increased activity in the introverted brain.


One theory goes like this: As the introverts have a naturally high level of activity in the anterior part of the brain, they are therefore not in need of significant extraneous stimuli. You could say that introverts are by nature is more or less chronically preoccupied by their own cognitive processes. Extroverts, by contrast, live in a form of chronic “activity deficit” and must therefore seek external stimuli to maintain a certain level of activity and function in their brains. – You can say that extroverts need stronger influences before the brain understands the message (e.g. more lemon juice to produce the same response), and so, a room without stimulants provokes the extrovert to produce his own entertainment.

Dopamine and the Brain


The higher activity in the brains of introverts is thought to be caused by dopamine, and it is believed that the introvert brains contains a greater quantity of dopamine. – And that the level of dopamine determines the degree of introspection or extroversion. Comparing this with the existing genetic studies of introverted and extroverted, it turns out that there are in fact structural differences between the dopamine receptors of introverts and extroverts.


Introverts thus find themselves in constant danger of being over-stimulated or “flooded” by dopamine. Introverts therefore exhibit certain empirical commonalities, however different their personalities may otherwise be.


Introverts hesitate before engaging in speech, in contrast to extroverts they often have a need for a “familiarization process” before they can “find their feet” in unexpected situations or in an interaction with strangers. Introverts works best alone and undisturbed and when they have time immerse themselves in their own thoughts and ideas. They communicate best-on-one, and when they socialize, they often prefer small intimate companies rather than large parties.


Looking at the demographic breakdown, introversion is evenly split between men and women. However, when we can still can speak of a cultural hegemony in favour of the out-going it is undoubtedly because introverts are a minority in the population at large, specifically around 25-40% of the population qualify as introverts, varying from strongly introverted, to certain introverts who are so close to limit that in practice they might as well be extroverted, in the scientific jargon known “ambiverts”.


Many introverts report that they experience their introversion as a handicap in a society where extroverts set the agenda: Because introverts may be softspoken and slow to adapt to new input, they are often overlooked in social situations and the outcome of the introvert’s carefully used cognitive processes never enter play, which is a shame because introverts are often able to tenaciously concentrate on a specific topic for long periods of time, and therefore can be incredibly creative and original.


So don’t let yourself be fooled by the introvert at times somewhat reserved people around you. There is a force inside them which harbours a rich and imaginative world, just waiting to be let out.

15 Comments

  1. Cathy says:

    I would like some citations or scientific papers which deal with the post above. I would like to examine closely the evidence.

  2. sara says:

    Yes, I second Cathy, please provide links to the research studies. Or at least journal & date where the studies were published.

  3. Mark Novbett says:

    Have to say, such sources would indeed be ground shaking for my debating ability.

  4. Bob says:

    Lol, modern research actually shows extraverts have greater dopamine levels. Modern theories define extraversion as increased reward sensitivity. People with social anxiety for example have lower d2 dopamine receptor concentrations, which in turn lowers their reward sensitivity

  5. Howard Glitt says:

    Lol, Bob that is also what his article says. Read again.

  6. Jennifer says:

    I to this very day struggle to know who I am in the I/E spectrum. I have been taking stimulant medication (I’m 23, started around age 6 or 7) of various forms (currently 72 mg of Concerta daily) for ADD. With that much containing of dopamine, I am usually self-stimulated by using my computer constantly, but I typically don’t want to go out and do anything fun. Once I am out, say at a wild party, I can blend and have fun however necessary, and I sometimes, when passionate about something, can talk and talk and talk. When I am tired, this doesn’t happen as much, nor as easily. My mom once told me that as a very young child, I was sometimes a bit of a wiggly worm. I had an insatiable interest in observing things and playing with things. I used wooden spoons to pretend to ice skate on the wooden floor at my grandmas with my younger brother, and made ice blocks and pretended to sail on them in the backyard. Creative, hands on stuff, mostly. I guess I don’t factor that in as much since it seems like typical stuff for kids to be encouraged to do. Then I went to video games and then computers. Now I use computers for knowledge. I don’t play video games at all these days (I still like them though). I’m in college, and my interests with knowledge on the internet cause me to take longer than necessary on my assignments. A form of distraction. Would that be a sign of my underlying extroversion, a symptom of my ADD, or just the sign of my N/intuitive side taking over an introverted person (me)? or am I sensor type… I do like philosophy and cosmology and theorizing about life origin and morals. I’m certainly not inhibiting myself from expression, as this post shows that I am willing to tell the public at large about myself. Is that an extroverted trait, or more a sign of a Feeling type (also my attribution to seeing truths and moral truths being basically a trait of F/Feeling, supposedly, instead of a thinking trait). Could I actually be an Introvert trapped by my complicated birth and prematurity, causing exaserbation of my inherited ADD genes? My father has it, but you’d usually never know. He does show signs of distraction, but not in terms of getting work done. If he is truly introverted, he does a good job in an extroverted lifestyle of sorts, as a self-employed doctorate Clinical Psychologist, stock trader, and business man. My mom seems more like an introvert. My brother seems like an extrovert since he is constantly chatting on xbox 360 live playing first-person shooter games. I can talk up a strong, but usually am retired to my bedroom, wasting away with my seeking of knowledge via the internet and guided by subconscious drives probably stemming from my underlying emotional needs, wasting time on one hand, and on the other hand, using the left over time to complete assignments, never getting out of the house to let my love for nature and interaction get properly utilized. So you see, I have sided with Introversion, but I don’t really know which one I am.

  7. Jonathan says:

    I wish researchers would stop claiming introverts are the minority. The largest sample so far demonstrates that the split is very close to 50/50. Or if you’re convinced that introverts are indeed the minority, I echo the above sentiments regarding citations: show us where you retrieved your information.

  8. Nina W says:

    “The open-plan office is a living nightmare for any introvert as it actively hinders concentration and furthers stress by going completely against the introvert’s preferred working conditions, namely peace, tranquillity and predictability.:

    I disagree with this. It’s more of a cultural apprehension than an individual one. Peace, tranquility, and predictability is more a function of the people in an open plan office than it’s actual physical configuration.

  9. Virgil Maro says:

    I disagree with Nina W. Being categorized an introvert, the open-plan office will be a nightmare regardless of the behavior of the other people within. The problem an introvert has with the situation is not that the people surrounding him are not behaving in a peaceful, tranquil or predictable way. Having to constantly acknowledge the presence of other people, whether through sight or subtle sounds prevents the ability of the introvert to retreat within in his own mind, where he prefers to be.

  10. Jennifer says:

    I categorize people according to whether they recharge by being with people or by being alone. I am outgoing and people think, naturally, that I am an extrovert. But I can only interact with people on an intense level for a limited time. Then I am emotionally exhausted until I can sleep or spend several hours alone, just reading or thinking.

    This is a problem when one has young children because the interaction is often intense and nonstop. Also, I teach writing classes, and I am intensely engaged with my students. When I am finished, it is like letting air out of a balloon.

    Two of my three children are true extroverts: they recharge by being with people. The other is like me and needs large amounts of time alone before she is ready to interact with people again.

  11. Gen says:

    As an introvert, (infj) even as friendly as I am, in an open office, I would never get any work done. I would feel obligated to say hello, and every interuption would mean low productivity because I transition poorly between activities and interuptions. I teach now, and have my cosmetology students turn off the radio when I am doing paperwork or grading. I often have to leave the room, because the busy-ness and noise as they socialize on hands on assignments is overwhelming. Give me lecture, where it mimics a one on one conversation. At the end of my day….i’m totally exhausted.

  12. Anon says:

    I only skimmed through the article but, if I’m not mistaken, there is no empirical evidence for the MBTI. There is some evidence for introversion vs. extroversion but not the Jungian idea of introverted vs. extroverted functions. Introversion is probably closer to the Big 5 understanding. I could be wrong. I see certain problems with the Big 5, though.

  13. admin says:

    There’s evidence for all of the four MBTI scales.
    What there isn’t evidence for is the division into the 16 types.

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