What makes an extravert?

Why do some people prefer adventure and the company of others, while others favour being alone? It’s all to do with how the brain processes rewards.

Will you spend Saturday night in a crowded bar, or curled up with a good book? Is your ideal holiday adventure sports with a large group of mates and, or anywhere more sedate destination with a few good friends? Maybe your answers to these questions are clear – you’d love one option and hate another – or maybe you find yourself somewhere between the two extremes. Whatever your answers, the origin of your feelings may lie in how your brain responds to rewards.

We all exist somewhere on the spectrum between extroverts and introverts, and different circumstances can make us feel more one way or the other. Extraverts, a term popularised by psychologist Carl Jung at the beginning of the 20th Century, seem to dominate our world, either because they really are more common, or because they just make most of the noise. (The original spelling of “extravert” is now rarely used generally, but is still used in psychology.) This is so much the case that some have even written guides on how to care for introverts, and nurture their special talents.

A fundamental question remains – what makes an extrovert? Why are we all different in this respect, and what do extraverts have in common that makes them like they are? Now, with brain scans that can record activity from deep within the brain, and with genetic profiling that reveals the code behind the constructions of the chemical signalling system used by the brain, we can put some answers to these decades-old questions.

In the 1960s, psychologist Hans Eysenck made the influential proposal that extroverts were defined by having a chronically lower level of arousal. Arousal, in the physiological sense, is the extent to which our bodies and minds are alert and ready to respond to stimulation. This varies for us all throughout the day (for example, as I move from asleep to awake, usually via few cups of coffee) and in different circumstances (for example, cycling through the rush-hour keeps you on your toes, heightening arousal, whereas a particularly warm lecture theatre tends to lower your arousal). Eysenck’s theory was that extroverts have just a slightly lower basic rate of arousal. The effect is that they need to work a little harder to get themselves up to the level others find normal and pleasant without doing anything. Hence the need for company, seeking out novel experiences and risks. Conversely, highly introverted individuals find themselves overstimulated by things others might find merely pleasantly exciting or engaging. Hence they seek out quiet conversations about important topics, solitary pursuits and predictable environments.

Betting brains

More recently, this theory has been refined, linking extroversion to the function of dopamine, a chemical that plays an intimate role in the brain circuits which control reward, learning and responses to novelty. Could extroverts differ in how active their dopamine systems are? This would provide a neat explanation for the kinds of behaviours extroverts display, while connecting it to an aspect of brain function that we know quite a lot about for other reasons.

Researchers lead by Michael Cohen, now of the University of Amsterdam, were able to test these ideas in a paper published in 2005. They asked participants to perform a gambling task while in the brain scanner. Before they went in the scanner each participant filled out a personality profile and contributed a mouth swab for genetic analysis. Analysis of the imaging data showed how the brain activity differed between extroverted volunteers and introverted ones. When the gambles they took paid off, the more extroverted group showed a stronger response in two crucial brain regions: the amygdala and the nucleus accumbens. The amygdala is known for processing emotional stimuli, and the nucleus accumbens is a key part of the brain’s reward circuitry and part of the dopamine system. The results confirm the theory – extroverts process surprising rewards differently.

When Cohen’s group looked at the genetic profiles of the participants, they found another difference in reward-related brain activity. Those volunteers who had a gene known to increase the responsiveness of the dopamine system also showed increased activity when they won a gamble.

So here we see part of the puzzle of why we’re all different in this way. Extrovert’s brains respond more strongly when gambles pay off. Obviously they are going to enjoy adventure sports more, or social adventures like meeting new people more. Part of this difference is genetic, resulting from the way our genes shape and develop our brains. Other results confirm that dopamine function is key to this – so, for example, genes that control dopamine function predict personality differences in how much people enjoy the unfamiliar and actively seek out novelty. Other results show how extroverts learn differently, in keeping with a heighted sensitivity to rewards due to their reactive dopamine systems.

Our preferences are shaped by the way our brains respond to the world. Maybe this little bit of biological psychology can help us all, whether introverts or extroverts, by allowing us to appreciate how and why others might like different things from us.

This is my BBC Future column from last week. The original is here

18 Comments

  1. kimhartinvenice
    Posted July 22, 2013 at 9:46 am | Permalink

    Extrovert, not extravert! Sometimes you get it right, and then not, but the title is defo wrong ;)

    • kimhartinvenice
      Posted July 22, 2013 at 9:48 am | Permalink

      oops – just seen that both are considered acceptable! Sorry :)

      • Januz
        Posted July 26, 2013 at 7:04 pm | Permalink

        actually, “extrAvert” is the correct psychological technical term and the linguistically correct term (in Latin there only exists “intro” and “extra”–not “extro”!)

        They are only both considered acceptable because too many people are using the wrong term (extrovert) :)

  2. Ivan
    Posted July 22, 2013 at 11:10 pm | Permalink

    What’s the point of differentiating between extraverts and introverts all the time when it’s a spectrum?

    My ideal holiday would be adventure sports with a small group of good friends.

    I think I’m right smack in the middle of the spectrum.

    Where is the line?

    Can depression push people towards being more introverted?

    • Posted July 24, 2013 at 4:18 pm | Permalink

      I would think having experienced depression that it could have the effect of making a normally extroverted person into an introvert. Situational depressions, for example, may knock a person down for a while, but then they recuperate and go back to being their “normal” selves which is probably somewhere on the extrovert scale. Major Depressive Disorder, on the other hand, is chemical or organic in nature, and scientists think has a lot to do with two or three neurotransmitters: Serotonin, Dopamine, and Monoamine Oxidase. Chemically depressed people are theorized to not produce enough of these transmitters so they get put on anti-depressants that help to keep the levels of these transmitters steady. These people are very likely to be introverts due to the nature of the disorder.

      I, myself, tend towards introversion, and always have. However, this is not to say that introverts don’t like to go out every now and then. Or take a trip to Tahiti :)

      I would think you are probably right that most people are somewhere in the middle or the statistical “norm.”

  3. Posted July 23, 2013 at 3:07 pm | Permalink

    Neat, an interesting puzzle. Based on no real studies I’m going to guess that introverts’ “inwardness” is more important in social situations. Adventure sports bring people into unspoiled wilderness which, in some ways at least, is more predictable than any human environment (that is to say, the natural world can be counted on every time to do what it does in a self-organized fashion; it’s highly reliable).

    I’d also guess adventure sports attracts both types, and the introverts are more likely to break ranks and survive accidents (Snow Falls comes to mind).

    • Posted July 24, 2013 at 4:30 pm | Permalink

      As an “introvert” who does enjoy adventure sports, it isn’t the predictability of nature that is the lure. It is the adrenaline rush you get from riding your bike down a hill you would normally hike on, or skiing down a steep hill at a high rate of speed without crashing. A lot of adventure sports are engaged in in a solitary manner. I used to mountain bike alone, or with one or two other people. It was the “high” that I was after, not necessarily the company of others.

      • Posted July 24, 2013 at 7:32 pm | Permalink

        That’s a decent point about solitary activity but it’s still anecdotal and does not address one of Stafford’s points:

        Conversely, highly introverted individuals find themselves overstimulated by things others might find merely pleasantly exciting or engaging.

        If introverts are easily overstimulated they’re not going to seek out activities that take them barreling down mountain cliffs. So that’s the question.

        Also are women more likely to represent the majority of introverts? Nature might be more appealing to women (but it lowers crime as well so males need it also).

        http://online.liebertpub.com/doi/abs/10.1089/eco.2010.0017

      • Posted July 24, 2013 at 9:00 pm | Permalink

        You make a good point. Introverts are less likely to find themselves barreling down mountain cliffs. But I think it is a different kind of stimulation. It is a physiological stimulation rather than a social setting which introverts may find themselves overstimulated by. I am easily overwhelmed by medium to large groups of people. I just feel uncomfortable, however, when bicycling be it on the road or in the mountains usually by myself, I feel comfortable. I am not overwhelmed by social stimuli.

        I do not know if women are more likely to be introverts in a psychobiological way, but, perhaps through the social “training” that women begin to receive early on in childhood, they become introverted so as not to appear to be “rocking the boat.”

      • Posted July 24, 2013 at 7:32 pm | Permalink

        tsk. Italics.

      • Posted July 24, 2013 at 9:00 pm | Permalink

        Sorry….

  4. Posted July 23, 2013 at 4:27 pm | Permalink

    Fascinating! I didn’t know that about the Eysenck study. I’ll definitely look up some more information about this. Thanks for the insight!

  5. Ney
    Posted July 24, 2013 at 11:05 am | Permalink

    In Cohen’s experiments (n=16 and n=17)they e.g. achieved correlation coefficients well above 0.50 (!) between brain activation measures and a paper-pencil extraversion scale? Personality scales are of limited reliabilty at best (and Cohen et al.’s claim that they achieved reliabilities – how determined? – of > 0.86 is surprising). Sorry, I don’t buy such results any more, not after the Simmons/Nelson/Simonsohn and the Ionannidis papers (BTW, from May 2013, Button KS, Ioannidis JPA et al.; Power failure: why small sample size undermines the reliability of neuroscience. Nature Reviews Neuroscience 14, 365-376). Since claims about the biological nature of “extraversion” were made so strongly in that BBC column, there must certainly exist a bunch of replications of the Cohen et al. results?

    The psychobabble of the older days was at least cheaper to produce than the current fmrt-genetics-neurobabble…

    • Posted July 24, 2013 at 4:25 pm | Permalink

      I tend to agree with you. Having had to take numerous statistics and data analysis classes to get my Sociology/Psychology degree, any study that has correlations above a certain level always make me wonder how big and how diverse was the experimental sample and the control sample. I would really question results from a study with n=16 and n=17 that achieved such a high correlation. I agree with you that if, in fact, this theory is indeed a theory and not a hypothesis, there should be numerous studies with larger sample sizes that have found the same results.

  6. immortaldarkphoenix
    Posted July 24, 2013 at 1:46 pm | Permalink

    So it turns out that extroverts are the one who are more stimulated. That would be consistant with my personal experience, as the reason I don’t frequent common extrovert activites and behaviours is because I find them uninteresting and underwhelming. Talking about IMPORTANT topics is more stimulating than inconcequential chat.

    As for the ‘predictable environments’ concept, I’ll slightly disagree and posit my own take: When I’m alone, the environment becomes a part of my self-image, and my inner being spills more; I’ll be more physically expressive, I’ll think alout, etc. It feels as though I am one with my surroundings. But when another person makes their presence known, it feels like an invasion; there’s a part of my assumed space that is consciously occupied, but is inaccessable to me. So it’s not exactly an issue of unpredictability.

    • Ben
      Posted July 29, 2013 at 5:35 am | Permalink

      immortaldarkphoenix, couldn’t have described any better what it’s like being by myself!

  7. Posted July 30, 2013 at 6:30 pm | Permalink

    Reblogged this on AlmostHumor By BlotterMonkey and commented:
    Seeing as how often I don’t fit easily into categories and I’m most usually the ‘exception to the rule’, I still like to pay attention to the categories that ‘other people’ gravitate towards so I am aware for communication & interaction when dealing with the people who do fit into categories… it has proven helpful socially & in business for me, and I recommend it to anyone wanting to understand people in general.
    But always keep in mind, people are not insects, we (well some)are fluid entities who creatively go out of bounds often when least expected.

  8. Ty
    Posted March 21, 2014 at 9:33 am | Permalink

    I’m beginning to think the main difference between introvert and extrovert is optimism and pessimism. My introvert friends can be more pessimistic than me when it comes to people. What fascinates them is how I came from the most abusive, toxic place and can still be as optimistic as I am – this observation helped me overcome some of my psychological problems yet… I still am extrovert. I like smiling at people and having them smile back. I like going out for no reason, and talk with no purpose vs. Introverts who have purpose.

    Some of my toxic introvert environment try to convince me I’m introvert because I don’t go out all the time and I don’t talk to random people (when they’re with me). My non toxic introvert friend would then remind me that he knows me better than the other one, that he’s seen me in social situations and it’s amazing how smooth I am.I then asked why I didn’t talk to many people when I was out with the toxic introvert, the non toxic replied with “because he turned your random social fun into a chore. he turned his own expectations into yours. Some introverts don’t understand extroverts, where they basically have no purpose for being outside”. I think the importance of understanding introvert vs. extrovert is so people get a long better. Empathy is a key to a better society. When an extrovert acts like an introvert, it’s because something is wrong.

    I don’t agree that the majority are extrovert because I live with 2 people who are introvert and know a lot of people who seem to have issues with their social life because they think they suck – which isn’t always true though… for some it’s definitely true, though that has nothing to do with introvert or extrovert, just toxic and non toxic.


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