Quick Quiz: Which of the following are signs of introversion?

Highly sensitive

Deep Thinker

Reflective

Introspective

Negative emotions

Socially Anxious

Defensive

Vulnerable

Always prefers solitude over social interaction

Answer: Not a single one.

Introversion is one of the most misunderstood dimensions of personality. Many people are not aware that the original definition of introversion, as posed by Carl Jung, is not how the term is used in modern personality psychology. Jung equated introversion with "inwardly directed psychic energy". Even the modern Wikipedia page for Extraversion and Introversion defines introversion as "the state of or tendency toward being wholly or predominantly concerned with and interested in one's own mental life."

But that's not introversion.

Common Misconceptions About Introversion

Whereas Jung based his definitions of extraversion and introversion on his own theory, experience, and intuition, modern psychology identifies personality dimensions empirically, based on what patterns of behavior tend to go together within individuals. Today, extraversion-introversion is one of the "Big Five" dimensions of personality, the other four being neuroticism, agreeableness, conscientiousness, and intellect/imagination.

The most common misunderstanding of the extraversion-introversion dimension is that introverts are more introspective than extroverts. In reality, introverts are not necessarily introspective and highly introspective people aren't necessarily introverted. In a recent analysis, Jennifer Grimes, Jonathan Cheek, and Julie Norem found that measures of Jung's conceptualization of "Thinking Introversion"-- introspectiveness, fantasy proneness, and having a rich inner life-- were not significantly correlated with Big Five scales of extraversion-introversion, including a need for positive stimulation and gregariousness.

In fact, what many people ascribe to introversion really belongs in the intellect/imagination domain [1]. Intellect/imagination represents a drive for cognitive engagement of inner mental experience, and encompasses a wide range of related (but partially separate) traits, including intellectual engagement, intellectual curiosity, intellectual depth, ingenuity, reflection, introspection, imagination, emotional richness, artistic engagement, and aesthetic interests.

Traits such as sensitivity and social anxiety are also not part of Big Five introversion-extraversion domain. To be sure, many people may think of themselves as introverted because they are highly sensitive. But research shows that sensory processing sensitivity is independent of introversion. The various manifestations of being a highly sensitive person-- inhibition of behavior, sensitivity to environmental stimuli, depth of information processing, and physiological reactivity-- are linked to neuroticism and intellect/imagination, not introversion.

What's more, there are lots of people who view themselves as "sensitive introverts", when they are really covert narcissists. These individuals are characterized by their sense of entitlement to social attention. Accordingly, they are hurt easily by the slightest remark of others, are hyper self conscious and self absorbed, and are frequently upset that others don't recognize their brilliance. Covert narcissism is strongly associated with neuroticism, not introversion.

Finally, there's a common misconception that all introverts enjoy solitary activities. However, that isn't a defining feature of introverts. Responses such as "Enjoy spending time by myself" and "Live in a world of my own" involve an equal blend of introversion and intellect/imagination. Contrary to popular conceptualizations of introversion, preferring to be alone is not the main indicator of introversion.

All of this, of course, leads to the major question: What is the essence of introversion? Let's explore the core of the extraversion-introversion dimension of personality.

The Core of Extraversion-Introversion

Extraversion-introversion comprises many related traits, including being talkative, sociable, friendly, gregarious, assertive, active, persuasive, and excitement seeking.

But what links all of these traits to each other?

One possibility is that the core of extraversion-introversion is simply sociability. Maybe extroverts are more social: plain and simple. However, the research doesn't support this conclusion. While it is well known that extraverts experience more positive emotions than introverts, extraverts tend to experience more positive emotions all throughout the day, regardless of whether the activity is social or solitary.

This doesn't mean that introverts experience more negative emotions during daily life (that's neuroticism). They are just lower in positive emotions. In fact, some researchers have suggested that "detachment" is a more accurate description of low extraversion than "introversion" [2].

Another possibility-- which has received more support-- is that the core of extraversion is sensitivity to rewards in the environment. Reward sensitivity refers to the tendency to experience "an incentive motivational state that facilities and guides approach behavior to a goal." As Colin DeYoung points out in an upcoming paper:

People who score low in Extraversion are not necessarily turned inward; rather, they are less engaged, motivated, and energized by the possibilities for reward that surround them. Hence, they talk less, are less driven, and experience less enthusiasm. They may also find levels of stimulation that are rewarding and energizing for someone high in Extraversion merely annoying or tiring (or even overwhelming, depending on their level of Neuroticism). Their reserved demeanor is not likely to indicate an intense engagement with the world of imagination and ideas, however, unless they are also high in [Intellect/Imagination]. Multiple studies are consistent with the reward sensitivity account of extraversion. In one set of studies conducted cross-culturally, Richard Lucas and colleagues administered traditional measures of extraversion, all of which involve reward. For example:

I enjoy talking to strangers

I prefer to be with people who are exciting rather than quiet

I like doing exciting things with people more than just talking quietly

They also administered a newly developed test that measured a preference for social over solitary activities. Crucially, they removed the reward value of the items. For example:

I always prefer being with others to spending time alone

I rarely spend time alone

I rarely go out of my way to find time for myself

Across four studies they found that the traditional measures of extraversion (that involved reward values) were all correlated with each other, and with positive emotions. But critically, their new scale (which removed rewards from the items) was not correlated with extraversion, or positive emotions. These results suggest that a mere preference for social interaction, independent of the reward/enjoyment of the interaction, is not the core of extraversion. In a followup study, Richard Lucas and Ed Diener found that extraversion was related to the tendency to enjoy pleasant situations (social and nonsocial) but was unrelated to reactions to unpleasant situations (social and nonsocial).

Therefore, it seems to be specifically the reward value of a situation, not the social nature of the situation, that predicts whether extraverts enjoy the situation more than introverts [3]. Consistent with this, several fMRI and EEG studies have shown that brain activity in response to a variety of rewards (favorite brands, humor, happy faces, monetary rewards and pleasant emotional stimuli) are associated with extraversion.

Not all behaviors are equally related to extraversion, however. The desire for positive social attention seems to be a particularly strong indicator of extraversion [4]. For example, Jacob Hirsh and colleagues found that taking into account the rest of the Big Five personality traits (agreeableness, neuroticism, conscientiousness, and intellect/imagination), the following 10 behaviors were most uniquely predictive of extraversion (from a list of 400 activities):

1. Told a dirty joke.

2. Planned a party.

3. Entertained six or more people.

4. Told a joke.

5. Volunteered for a club or organization.

6. Tried to get a tan.

7. Attended a city council meeting.

8. Colored my hair.

9. Went to a night club.

10. Drank in a bar.

Why might the drive for social attention be so strongly linked to extraversion? One possibility is that many human rewards are social in nature. Our complex social lives are probably the dominant force in human evolution, driving the evolution of intelligence, creativity, language, and even consciousness. The human reward system, therefore, most likely evolved to be particularly responsive to social rewards.

Indeed, one of the most important gateways to rewards (e.g., money, power, friends, alliances, mates, exploration of the environment) is the ability to capture the attention of other people. Along these lines, some researchers have suggested that extraversion represents a high-intensity strategy for gaining social attention.

There are costs to extraverted behavior, however. This includes time and energy that could be invested in other activities, such as accomplishing a goal (conscientiousness) or engaging with ideas and imagination (intellect/imagination). There is also the risk that inappropriate attention-seeking behavior can fall flat, leading to reduced attention-holding power. Finally, high levels of exploration of the environment can expose extraverted individuals to increased physical risks. For instance, extraverts are more likely to be hospitalized due to accident or illness, and are more likely to become involved in criminal or antisocial behaviors and get arrested.

From an evolutionary perspective, there's a reason why both introversion and extroversion evolved, as both have fitness benefits and disadvantages depending on the context.

The Engine Behind Extraversion-Introversion

It's important to distinguish, however, between the most prominent behavioral manifestation of extraversion (desire for social attention) and the core underlying mechanism of extraversion (reward sensitivity). Even though reward sensitivity need not be limited exclusively to social situations, high reward sensitivity likely motivates extraverts to seek out potentially rewarding positive social interactions, and fuels them to display behaviors that will increase social attention (e.g., friendliness, smiling, high energy, loudness, exhibitionism, positive emotions).

From a biological perspective, reward sensitivity is likely governed by dopamine. While dopamine is involved in a variety of cognitive and motivational processes, the unifying function of dopamine is exploration. According to Colin DeYoung, "the release of dopamine, anywhere in the dopamingergic system, increases motivation to explore and facilitates cognitive and behavioral processes useful in exploration."

Dopamine isn't only related to extraversion. Dopamine is also causally related to intellect/imagination, although differences in openness are more likely to reflect variation in salience coding neurons (which increase curiosity and the desire to obtain information). In contrast, extraversion is more likely to reflect differences in the operation of value coding neurons (which indicate the incentive reward value of attaining a specific goal). Indeed, fMRI studies have found that extraversion is associated with greater volume of the ventromedial prefrontal cortex (vmPFC), a region known to be involved in coding the value of rewards.

This probably explains why a lot of introverts notice that they often need to be alone to recharge their batteries after vigorous social interactions, whereas extraverts appear to gain energy from social interactions. This can be explained by dopamine's function in energizing potentially rewarding social interactions, as well as its role in overcoming the cost of effort. For introvert's, such interactions are more effortful and tiring due to their less active reward system [5].

Are You an Introvert?

Researchers have found that the various facets of the introversion-extraversion domain can be boiled down to two related but separate aspects: enthusiasm and assertiveness.

Enthusiasm encompasses traits like sociability, friendliness, self-disclosure, gregariousness, and positive emotionality. Enthusiasm is primarily about social affiliation, but goes beyond sociability to include positive emotions, more generally, like joy, exuberance, and excitement [6]. Assertiveness encompasses traits like leadership, dominance, provocativeness, activity, talkativeness, and persuasiveness. Assertiveness is more about social status than social affiliation.

These 20 items have been found to accurately capture these major aspects of the introversion-extraversion domain of personality. Rate each item from 1 (doesn't apply to me at all) to 5 (really applies to me):

1. Make friends easily. __

2. Am hard to get to know. __

3. Keep others at a distance. __

4. Reveal little about myself. __

5. Warm up quickly to others. __

6. Rarely get caught up in the excitement. __

7. Am not a very enthusiastic person. __

8. Show my feelings when I'm happy. __

9. Have a lot of fun. __

10. Laugh a lot. __

11. Take charge. __

12. Have a strong personality. __

13. Lack the talent for influencing people. __

14. Know how to captivate people. __

15. Wait for others to lead the way. __

16. See myself as a good leader. __

17. Can talk others into doing things. __

18. Hold back my opinions. __

19. Am the first to act. __

20. Do not have an assertive personality. __

Now reverse code items #2, #3, #4, #6, #7, #13, #15, #18, and #20 (replace 5=1, 4=2, 3=3, 2=4, and 1=5).

Now take the average of all the items.

Results:

If you averaged 3.0 or less, you are probably an introvert.

If you averaged between 3.1-3.8, you're probably an ambivert.

If you averaged 3.9 or higher, you're probably an extravert.

(Note: If you score the first 10 questions and the second 10 separately, you can assess the engagement and assertiveness aspects of extraversion separately. Some ambiverts are high in enthusiasm (first 10) but low in assertiveness (second 10), and vice versa.)

Conclusion

It is my hope that this article helps you understand yourself better. There are many ways you differ from others. However, it doesn't all come down to the extraversion-introversion dimension. Maybe you realized that instead of being an introvert, you are actually an extravert (enthusiastic and assertive) who is also a highly sensitive person. Or maybe you realized that you are really an extravert who likes to daydream and reflect deeply about ideas. Or maybe you even realized you are actually an introvert who daydreams a lot, or an introvert who doesn't have a vivid fantasy life but is high in intellectual curiosity. All of these combinations are possible, and more.

But a first step is shedding outdated and inaccurate notions of what it means to be an introvert.

© 2014 Scott Barry Kaufman, All Rights Reserved.

Acknowledgement: Thanks to Colin DeYoung for his feedback on this article, and for having so many discussions with me about this topic.

[1] What I refer to as "intellect/imagination" is frequently referred to in the personality psychology literature as openness to experience. I decided to label the domain intellect/imagination to emphasize that this domain of personality represents openness to new inner mental experiences, not just any kind of experience. In fact, extraverts are more likely to be open to new behavioral experiences that relate to exploring the external environment.

[2] This doesn't mean that introverts don't ever experience positive emotions, or don't enjoy social interactions. Research shows that both extraverts and introverts experience more pleasant affect in social situations than in nonsocial situations. This does have implications for happiness and subjective well-being, however. One of the most robust findings in the happiness literature is that extraversion and happiness are strongly related to each other. A major cause is most likely the positive emotions that extraverts feel on a more regular basis.

[3] It should be noted that introverts also want to experience pleasant emotions; it's just that what they tend to experience as pleasant is different than what extroverts report as pleasant. Also, a lack of negative emotions can also be experienced as pleasant, even if it's not specifically positive.

[4] This also applies to how extraversion is measured by the Myers-Briggs Type Indicator (MBTI) test. The MBTI extraversion-introversion scale only includes items relating to being talkative, gregarious, and sociable (vs. quiet and reserved). Since there's not a single item on the MBTI extraversion-introversion dimension that mentions being introspective or reflective, even the MBTI doesn't measure Jung's original conceptualization of the term!

[5] To be sure, extraverts also get drained by too many social interactions (even though their threshold for exhaustion during rewarding social interactions is higher).

[6] Of course, those scoring low in the enthusiasm aspect of extraversion may still show enthusiasm for specific activities. For instance, an introvert who scores high in intellect/imagination will likely be enthusiastic about engaging with ideas and imagination.

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