Extraversion
Also, extroversion
January 25, 2022 — February 21, 2025
Why am I interested in extraversion?
Many reasons, but I should disclose that I have skin in this game: I am an extrovert. I regularly rank in the top bracket of extraversion in personality tests. Extraversion is 50-70% of my whole personality, depending on which definition of extraversion you take.
In some ways, this notebook is to remind me that not everyone is like me. The world, I must remind myself, is packed full of introverts.
If I have little evidence of the existence of introverts from e.g. sightings at parties, it is because introverts are, I assume, quietly reading books at home in suburban cul-de-sacs or meditating in the forest or something. If introverts are not living in a glass shopfront on a major road in a major city like me, I should nonetheless try to remember that they exist. I do not doubt the existence of nocturnal marsupials although I have seen few of them, and I can persuade myself that dark matter is real even though I have never seen it. Same thing with introverts.
Extraversion is a term coined by Jung (Jung 1923) that has stuck around, and thus may be useful in some way. R. Depue and Fu (2013) mentions its durability as a psychometric concept into the modern era:
Extraversion represents a higher-order personality trait that has been identified in virtually all classificatory systems of the structure of personality, including Eysenck and Gray’s models (Gray 1994), the Five-Factor model (Costa Jr. and McCrae 2000), Tellegen’s Multidimensional Personality Questionnaire (MPQ) model (Tellegen and Waller 2008), and Zuckerman’s Alternative Five-Factor model (Zuckerman 2002). The phenomenology of extraversion is described similarly in all of these models, and is characterised by adjectives that connote a state of positive affect and strong motivation of desire and wanting, as well as by feelings of being excited, enthusiastic, active, peppy, strong, confident, and optimistic (Watson and Tellegen 1985; Berridge 2004).
1 Dopamine and extraversion
R. Depue and Fu (2013) summarises a hypothesis of relatively low-level characterisation of extraversion (I do not have time to link in all the citations right now) stemming from their own research programme (R. A. Depue et al. 1994). They hypothesize that extraversion is closely linked to how the brain processes rewards through dopamine. Dopamine is a chemical messenger in brain pathways that drive motivation and pleasure. The key findings are:
Brain Reward System: Extraverts have more responsive dopamine systems in brain regions that detect rewards (like the nucleus accumbens and ventral tegmental area, whatever those are). These areas help us learn which contexts (e.g., places, situations) predict positive outcomes.
Context Learning: When environments are paired with rewards, extraverts build stronger mental associations between those contexts and feeling good. This happens because dopamine strengthens connections in the brain, making reward-related memories stick.
Experiments: In studies, people took a dopamine-boosting drug (methylphenidate) in specific lab settings. High extraverts later showed:
- Faster movement (e.g., finger-tapping)
- Better mood and focus in those same settings—even without the drug
- Improved short-term memory for tasks linked to rewards
Low extraverts didn’t show these effects, suggesting their dopamine systems react less strongly.
This suggests a model of extraversion in terms of reward-seeking.
- Extraverts need smaller rewards to feel motivated (like a “lower volume knob” for dopamine activation).
- Over time, their brains wire themselves to seek out rewarding contexts more often, creating a self-reinforcing loop. This is one reason that extraversion might stay stable throughout life (I’m not sure why we need this stability hypothesis?)
Taken together this [TODO clarify]
The purported real-world implications are
- Explains why extraverts chase novelty and handle repetitive tasks better — their brains are primed to link effort with rewards.
- Could help understand why some people develop addictions (overactive reward-seeking) or depression (low reward responsiveness).