The Science of Personality, What Drives Introversion and Extraversion

The Real Science of Introversion
Answering the questions of what makes us feel good about work has been the object of endless fascination. In business, uncovering what motivates us is a major lever to affect results. The popularity of Myers-Briggs type assessments is at an all time high. “This year alone, there have been close to 100 certification sessions,” says an article distributed with the October 18 issue of Learning Habit.

Our interest in personality types has wider appeal than the promise of business applications. It's become quite common to talk about being introverted or extraverted* in social circles as a way to explain how we make sense of the world. While extraverts have enjoyed their share in the spotlight, the recent work of Susan Cain is helping unlock the power of introverts.

But we are likely misunderstanding both dimensions. To learn what drives us, we need first to understand the science behind the labels.

Understanding the science of personality

Dr. Scott Barry Kaufman researches the science for the measurement and development of imagination, creativity, and play to answer questions such as why learning actively leads to well being. He is scientific director of the Imagination Institute in the Positive Psychology Center at the University of Pennsylvania.

In a recent lecture on introversion, he says:

Introversion is one of the most misunderstood, yet one of the most important dimensions of human personality. The introversion/extroversion of human personality is one of five major personality traits psychologists have identified in recent years. 

We also have neuroticism, which is associated a lot with anxiety, associated with rumination, things of that nature. We have agreeableness — how nice are you, how much do you pay other people compliments, how much do you listen to them. Conscientiousness — how much do you work towards your goals. With extraversion and introversion dimensions, and then we have openness to experiences — how much you are open to your inner stream of consciousness, inner stream of fantasies and ideas, how much you reflect on the world around you.

Each of us has a combination of varying degrees of these five elements of personality. One of the most interesting finding by modern psychologists is that personality is a hierarchy, says Kaufman:

At the top, we have two fundamental dimensions of human personality. We have stability, which is how much do you like order in your life, how much do you like things to go in a set way. And you have plasticity, which is how much do you like to engage in the world. This plasticity part encompasses extraversion and openness to experience.

But there are different ways that you can engage in the world. You can be really high in behavioral engagement, which is going out in the world and being really excited about everything in your environment… it has to do with behavioral engagement — a lot of enthusiasm, you are being pulled by potential rewards in your environment. And then there is openness to experience, which is another form of engagement. It is very important for engaging in your rich fantasies, in deep thinking, your love of learning, your intellectual curiosity.

Two main dimensions at the top and various aspects of how the five levels manifest themselves. For example, says Kaufman, “neuroticism has an emotional aspect of withdrawal and volatility. The introversion/extraversion dimension has this enthusiasm and a general form of assertiveness.” And underneath them, there are even more finely differentiated elements. For example, “under assertiveness, we may be assertive in some settings and not in others,” it's situational.

Highlighting represents how:

  • Most of the stability aspect of personality are driven by serotonin#, the lighter circles in the image above
  • The bolder circles denote traits driven by dopamine#

We know dopamine as “the sex, drugs, and rock'n roll molecule,” but that is incorrect, says Kaufman:

Dopamine is not about pleasure in itself. It doesn't guarantee that you will enjoy anything. All that it guarantees is that you'll be excited by the possibility of it. Dopamine increases your sensitivity to the reward value of information

Those who are really high on extraversion have a very quick trigger mechanism for the reward system when it comes to potential rewards in their environment. We are talking about evolutionary-driven ancestral rewards… things like social attention, social status, money, sexual opportunities… food quantity.


Introversion is a preference for quiet, for being reserved, being more cautious about your environment. But there is a second major pathway discovered in the brain in recent years, also a dopamine pathway, which is not tied to ancestral rewards.

We share this ancestral rewards dimension with other animals. A second reward system is associated with the potential reward value of information. This means we can become excited about the potential reward value of understanding things. Gaining information is a reward potential that has developed in humans, says Kaufman.

Our “Imagination Network” is active when we turn our limited spotlight of attention inward, when we reflect deeply on things rather rather than jumping to conclusions. Our ability to imagine our future is also associated with our ability to imagine what it's like for others — compassion.

Imagination Network

Poets, writers, anyone who spends time alone thinking and understanding information can reap benefits from the Imagination Network. Kaufman says we often label shyness as introversion incorrectly. Shyness comes from the neuroticism aspect of personality. It could apply to introverts and extraverts. Another misconception is that introverts don't like people. That's part of the agreeableness dimension of personality.

It is the nature of the reward value system that drives our personality traits and what interests us.

Watch the full lecture below.

Dr. Scott Barry Kaufman, Scientific Director at the Imagination Institute, University of Pennsylvania from Quiet on Vimeo.

 For a more in depth understanding of introversion, I recommend Susain Cain's Quiet: The Power of Introverts in a World That Can't Stop Talking.


[* Dr. Kaufman has also conducted research on the origins of the spelling for this word.]

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