Am I an Introvert or an Extrovert?

After reading numerous papers on psychology and neuroscience over the years, I have found Professor Robert Sapolsky’s discussion, “Introversion/Extroversion Neuroscience,” to offer the most compelling explanation of the distinction between introversion and extroversion. https://www.youtube.com/watch?v=Wf8lzAtRwrY

Here is a summary of his presentation:

The Neuroscience of Introversion and Extroversion

The distinction between introversion and extroversion is one of the oldest subjects in personality psychology. Extroverts are generally described as socially active, energetic, verbal, assertive, enthusiastic, sensation-seeking, and attracted to novelty, while introverts tend to be quieter, more reserved, reflective, and comfortable with solitary activities.

From a neuroscience perspective, however, the distinction is much more complicated. Professor Robert Sapolsky argues that much of the existing neurobiological literature may tell us less than researchers once assumed. The central problem may not be neuroscience itself, but how researchers define and measure reward.

Introversion Is Not Shyness

Introversion is not the same as shyness or social anxiety. A person can be introverted without fearing social situations, just as an extrovert can be socially anxious.

Introversion and extroversion are better understood as tendencies in where people direct attention, what kinds of stimulation they seek, and what they find rewarding. They also exist on a continuum rather than as two rigid categories.

A useful distinction is:

Extroversion tends to derive gratification from the external world, while introversion tends to derive more gratification from one's internal world.

This shifts the question from whether someone is sociable to something deeper: What kinds of experiences does that person find rewarding?

What Neuroscience Initially Suggested

Some studies have suggested that introverts show greater average activation in parts of the prefrontal cortex, regions associated with planning, deliberation, and complex thought.

Extroverts, by contrast, have sometimes shown more activity in areas involved in social processing, including the anterior cingulate cortex and temporoparietal junction.

Introverts have also sometimes shown greater amygdala activation in unfamiliar situations, suggesting that novelty may produce stronger vigilance or arousal.

Sapolsky cautions, however, that these findings are not strong enough to define a clear "introvert brain" and "extrovert brain."

The most consistent evidence concerns dopamine and reward.

Dopamine, Reward, and Extroversion

Extroverts tend, on average, to show greater responsiveness to reward.

This involves the brain's mesolimbic dopamine system, including structures such as the ventral tegmental area and nucleus accumbens, which are important for motivation, anticipation, reinforcement, and reward-directed behavior.

Early brain-imaging experiments suggested a relatively simple pattern: when introverts and extroverts received the same reward, extroverts often showed stronger activation in reward circuitry.

For example, when participants gambled for money, extroverts tended to show a larger reward response. Similar findings appeared with some forms of social reward.

This led to the idea that:

Extroverts have more reward-responsive dopamine systems than introverts.

That could help explain their greater attraction to novelty, excitement, achievement, social attention, and external stimulation.

But the picture becomes more complicated when we examine what dopamine actually does.

Dopamine Is More About "Wanting" Than "Liking"

Dopamine is often described as a pleasure chemical, but it is more closely related to wanting, anticipation, motivation, and pursuit.

This creates an important distinction between appetitive and consummatory behavior.

Appetitive behavior concerns wanting and pursuing a reward. Consummatory behavior concerns enjoying it once it has been obtained.

The differences between introverts and extroverts appear stronger in the first category.

Extroverts may therefore not necessarily enjoy rewards more. Instead, they may experience a stronger motivational pull toward certain anticipated rewards.

The distinction may be less about pleasure and more about the intensity of wanting.

What Counts as a Reward?

This is where Sapolsky identifies a major problem in the research.

Studies often use rewards such as money, applause, social approval, public recognition, smiling faces, or exciting events. If extroverts show stronger dopamine responses, researchers may conclude that extroverts are simply more responsive to reward.

But what if these experiments disproportionately use rewards that extroverts already prefer?

Imagine giving a speech and receiving loud applause from a large audience. An extrovert may find this highly rewarding. An introvert may appreciate the approval but find the intensity uncomfortable or unimportant.

If the extrovert shows a stronger dopamine response, have we really shown that extroverts respond more strongly to reward?

Perhaps we have only shown that they respond more strongly to extrovert-oriented rewards.

What If the Reward Fits the Introvert?

Now imagine a different situation.

A participant listens carefully to someone describing a personal difficulty and offers thoughtful advice. At the end, the person quietly says:

"Thank you. What you said genuinely helped me."

For some people, that intimate acknowledgment may be far more rewarding than public applause.

Likewise, replace tickets to a loud sporting event with unlimited access to a bookstore, an exhibition devoted to a specialized interest, uninterrupted creative work, or the opportunity to solve a difficult intellectual problem.

The question changes completely.

Perhaps introverts do not possess weaker reward systems.

Perhaps they are simply rewarded by different things.

If so, a great deal of research may contain a built-in bias. Researchers may have repeatedly compared introverts and extroverts using rewards that disproportionately appeal to extroverts.

The conclusion then becomes circular:

Extroverts respond more strongly to the kinds of rewards extroverts prefer.

That is very different from proving that they possess stronger reward systems overall.

Agentic Versus Affiliative Reward

Personality research also distinguishes between agentic and affiliative motivation.

Agentic motivation concerns achievement, status, influence, competition, visibility, reputation, and personal success. Its rewards include winning, receiving applause, gaining recognition, and being seen as impressive.

These are exactly the kinds of rewards often used in studies of extroversion.

Affiliative motivation, by contrast, concerns warmth, trust, gratitude, intimacy, kindness, and meaningful personal connection.

The reward is not:

"Everyone thinks I'm impressive."

It may instead be:

"I genuinely helped this person."

Sapolsky suggests that affiliative rewards may overlap more strongly with traits commonly associated with introversion.

An introvert may care deeply about people while caring very little about social spectacle.

A Bias in the Research

If experiments mainly use rewards involving money, excitement, status, competition, or public approval, they may unknowingly be built around an extroverted definition of reward.

The experiment then effectively asks:

Who responds most strongly to an extroverted reward?

And unsurprisingly, the answer is often extroverts.

A better approach would expose people to a wide range of rewards and first determine what each individual actually values.

These could range from public recognition to quiet appreciation, from a crowded sporting event to an afternoon in a bookstore, or from winning a competition to solving an intellectually difficult problem.

Only then could researchers determine whether extroverts truly have stronger reward responses, or whether different personalities simply possess different reward landscapes.

Why the Picture Has Become Less Clear

Early brain-imaging studies often used relatively small groups. As technology improved and studies became larger, many previously clear differences became weaker and more complicated.

This does not necessarily mean the earlier research was entirely wrong. It means larger datasets reveal more variation.

There may be no single "introvert brain" or "extrovert brain."

Personality may instead emerge from overlapping differences in reward sensitivity, motivation, arousal, social orientation, cognition, temperament, experience, and context.

The closer neuroscience looks, the less convincing a simple binary becomes.

Society's Bias Toward Extroversion

Society often rewards extroverted traits such as visibility, assertiveness, networking, enthusiasm, and social confidence. As a result, extroversion can appear to represent a fuller or more engaged way of experiencing life.

Introversion can then be misinterpreted as less motivation, less excitement, or less reward responsiveness.

But introversion may not represent less experience. It may represent a different distribution of attention and reward.

An introverted person may experience enormous satisfaction from learning, contemplation, mastery, reading, creating, solving problems, developing expertise, maintaining a few meaningful relationships, or quietly seeing sustained effort bear fruit.

These rewards may produce fewer outward signs of excitement, but that does not make them less significant.

An Evolutionary Perspective

Sapolsky also raises an evolutionary question.

Extroverted behaviors have obvious parallels in other primates: dominance, competition, alliance formation, mating displays, group participation, social bonding, and status seeking.

These behaviors are evolutionarily ancient because survival and reproduction depend heavily on navigating the external social world.

Deep introspection is much harder to identify in other animals.

This suggests that externally oriented motivational systems may be very ancient, while the rich internal psychological world associated with human introspection may depend more heavily on recently evolved cognitive capacities.

Humans can derive meaning from abstract thought, imagination, artistic creation, knowledge, private reflection, and intellectual discovery.

From this perspective, introversion should not necessarily be viewed as a weaker form of extroversion. It may reflect distinctly human capacities for obtaining gratification from a rich internal world.

A Different Understanding of Introversion and Extroversion

The most interesting conclusion is not that extroverts possess "more dopamine" or that introverts have weaker reward systems.

A more useful possibility is that different personalities assign value to different experiences.

Extroverts may be especially responsive to novelty, excitement, attention, achievement, status, and externally visible success.

Introverts may place greater value on intellectual discovery, mastery, meaningful one-to-one interaction, reflection, autonomy, private accomplishment, and seeing sustained effort gradually produce results.

The fundamental question may therefore have been framed incorrectly.

Instead of asking:

 "Who responds more strongly to reward?"

neuroscience may need to ask:

"What does this person experience as rewarding?"

An introvert quietly reading, solving a difficult problem, pursuing an intellectual interest, helping another person, or watching years of work finally bear fruit may appear less stimulated than an extrovert receiving enthusiastic public recognition.

Internally, however, the experience may be just as significant.

The difference may not be how much reward people experience, but where they find it and what motivates them to pursue it.

On a personal note:  I’m glad to have discovered that I am, indeed, an introvert—a seeker of information, knowledge, and understanding rather than external rewards. 
I do not respond particularly well to loud gatherings, nor do I place much value on glorifying praise or dopamine-driven compliments. 
Instead, I find far greater satisfaction in quiet reflection, meaningful discovery, and the simple fulfillment of seeing my efforts bear fruit.

© 2000-2030 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a fife year copy right.
Library of Congress Card Number: LCN 00-192742 ISBN: 0-9703195-0-9