An essay composed of stray thoughts strung together, featuring a lazy and dishonest attempt at citation.

There is one main difference between Jung’s concept of introversion/extraversion and that of the Big 5 model, which is considered the “Gold Standard” of modern personality psychology. In brief, Jung’s version is bipolar while the Big 5 uses a unipolar spectrum. This means that Jung juxtaposes introversion and extraversion as two different and opposed principles. Each one occupies a certain domain, namely that of the psychological “interior” and that of relation with the outside world. Neither one is exactly reducible to the other. Both have positive manifestations, meant not as a valuation, but technically: While from the outside, the extravert appears to be more engaging and the introvert more withdrawn, internally the introvert is also actively seeking something, but something different from external objects and object-relations. The introvert “seeks the subject”, or the meaning contained within—and native to—their own psyche [1].

Meanwhile, Big 5 introversion is essentially a lack of extraversion. Extraversion is characterized by several facets: gregariousness, assertiveness, activity-seeking, enthusiasm, and more. Depending on the study and framework used, introversion—technically “low extraversion”—is mildly correlated with neuroticism, a separate scale measuring a propensity for negative emotions and moods like anxiety and depression. But overall, introversion is presented as a second-class trait, a lack rather than an active component of the personality. Other traits that are intuitively associated with introversion, like imaginativeness, are the domain of trait Openness in the Big 5. A handful of benefits are observed in introversion, such as a tendency to do better in academia, possibly because of a greater ability to focus on one or two topics for long stretches of time, and because introverts participate in fewer distractions [2]. But nowhere is introversion explicitly associated with interiority. That said, the statistics—based on a linguistic study of personality such as the Big 5—would have trouble showing this. It’s been argued that the Big 5’s lexical basis makes it prone to pro-social biases, since language itself is a pro-social tool [4]. Therefore, extraversion would make a bigger “splash” in the factor analysis than an asocial trait like introversion. Furthermore, to an observer, inwardness is often synonymous with opacity. Introverts are best defined by what they don’t reveal about themselves. A scientific investigation of introversion as a first-order trait would have to progress in more creative directions.

What does the non-psychometric research on introversion/extraversion say? Studies have found that the mesocortical dopamine reward circuit, dubbed the “seeking” or “approach” system, is more active in extraverts than in introverts [3]. The reward system is what gives us an inner incentive to pursue certain activities and acquire things we want. It plays a part in attention by ‘imbuing’ things with salience, making us expectant of a reward, drawing our energy and gaze towards them. It is also the basis of addiction, as all addictive drugs potentiate the circuit in various ways. According to Panksepp, the seeking system does not correspond to pleasure exactly, but to the emotion of enthusiasm [5]. Enthusiasm, as you might recall, is one of the major sub-facets of Big 5 trait extraversion.

All this to say that according to this research, the extravert is more expectant of reward, more incentivized to pursue and explore things in the environment, more enthusiastic, and furthermore that this might be the mechanical basis of trait extraversion. Introverts would have less activity of this system. My question is this: Is the difference so linear? It’s known that all people exhibit a wide array of behaviours and emotions, but that the stable psychometric traits best describe the ‘average point’ of those behaviours [citation needed]. Jung also thought the two types of behaviour are highly context-dependant, so that an introvert in an easy and familiar environment would be indistinguishable from an extrovert, and an extrovert left to ponder their often-ignored complexes would be anxious and inhibited. Furthermore, he thought that it is not that the magnitude of a bout of enthusiasm that is different, but that introverts and extraverts get enthusiastic about different things.

First, I will round out a relation between the seeking system and Jungian psychology. In psychoanalysis, the fact that meaning is never inherent in the object but synthesized by the subject manifests itself as “projection”. It is the individual nervous system that imbues things with salience, as if the same person were both chasing and holding up the carrot-on-a-fishing-pole. Jung calls the function that creates these projections the Anima, because in his analyses of dreams and fantasies as well as mythology and folklore, he often found it personified as a woman (or as a man in the case of a woman—the Animus). For example, the Hindu goddess Maya, who spins the web of illusions that draw people out into the play of life. And this is exactly what the seeking system does: it produces the feeling of expectancy that spurs us into activity, into exploration, work, love, and sex.

According to Jung—and this is where I think his ideas get the most complex, and as a result unlikely, but they are fascinating to share—the Anima is ‘more unconscious’ in the psyche of the extravert. Since they are more interested in things in the environment than the inner workings of their mind, the Anima—which is one of these ‘inner workings’—sits outside of the field of awareness. To perform its function, it accesses the consciousness of the extravert in a roundabout way. It projects all kinds of personal contents onto external objects, so that these objects accrue the meaning contained in the extrovert’s own soul. This contributes to the heightened salience of the outside world for the extravert. Meanwhile, since the introvert spends more of their waking life absorbed in their own psyche, they gain more direct access—not in explicit awareness, but in intimations—of the functioning of the Anima. Their attention is directed not at external projections, but at the Anima image itself and the meaning it carries internally. Salience is contained in ideas and feelings, and is extended to the outside world only insofar as things—be they books, artwork, activities, or people—correspond to and evoke this inner reality.

If we put aside the more nebulous ideas about the location, function, and image of the Anima archetype, we can generate a simple hypothesis: Introverts and extraverts get enthusiastic about different things, based on a different principle. The relative difference in the quantity of seeking system activity might be accounted for by introverts encountering salient stimuli with a lower frequency rather than a lower amplitude—or, that the experimental stimuli are geared more towards the extroverted psychology. Jung expressed the context-dependency of this dynamic in a sort of allegory: An introvert and an extravert approach a castle in the countryside. The extravert expects to meet all sorts of positive things on the inside—gracious hosts, feasts, adventures—and gets excited about entering. The introvert, more anxious with respect to the environment, is worried about guard dogs and cantankerous keepers. However, they go inside. There they find it is filled with books and scrolls like an old library. The introvert’s eye is caught by this and that and scurries about in excitement. The extravert, meanwhile, is severely disappointed. This is not nearly as stimulating as they expected. They even start to become sour and cranky, more like the demeanour of a defensive introvert than their normal sanguine state. The extravert is drawn to the possibility of excitement and adventure; the introvert, to elaborations on ideas that are personal to them.

In this essay I’ve made a small attempt to reconcile Jung’s older and more theoretical ideas about introversion with modern psychometric and neuropsychological research. My emphasis was on creating a unified conceptual interpretation of the facts and theories involved. Specifically, I think Jung’s ideas about introversion/extraversion as the direction of interest/flow of libido, as well as the projection-making Anima, have the potential to correspond well with studies of the mesocortical reward circuit or “seeking” system, provided we make a deeper study of the potential context-dependency of this system. If this turns out to be correct, it would open more questions about the “why” of this personality dimension, since the relative difference in seeking behaviour would be the manifestation of a deeper basis rather than the basis itself. Perhaps it is, as Jung suggested, something analogous to r/K selection theory [6]: the opposite survival tactics of “high defenses and low fertility” versus “low defenses and high fertility”. In any case, I think it is worth returning to the investigation of introversion/extroversion as a bipolar dimension, since the psychometric, linguistic Big 5 version doesn’t seem to do justice to the introverted type.

Works cited: Lazy but getting there edition

[1] Jung, C. G., & Baynes, H. G. (1926). Psychological types: Or, The psychology of individuation.

[2] ENTWISTLE, N. J. and ENTWISTLE, D. (1970), THE RELATIONSHIPS BETWEEN PERSONALITY, STUDY METHODS AND ACADEMIC PERFORMANCE. British Journal of Educational Psychology, 40: 132–143. doi:10.1111/j.2044-8279.1970.tb02113.x

[3] Depue, R., & Collins, P. (1999). Neurobiology of the structure of personality: Dopamine, facilitation of incentive motivation, and extraversion. Behavioral and Brain Sciences, 22(3), 491-517.

[4] Trofimova, I. (2014). Observer Bias: An Interaction of Temperament Traits with Biases in the Semantic Perception of Lexical Material. PLoS ONE, 9(1), e85677. http://doi.org/10.1371/journal.pone.0085677

[5] Satoshi Ikemoto, Jaak Panksepp, The role of nucleus accumbens dopamine in motivated behavior: a unifying interpretation with special reference to reward-seeking, In Brain Research Reviews, Volume 31, Issue 1, 1999, Pages 6-41, ISSN 0165-0173, https://doi.org/10.1016/S0165-0173(99)00023-5.

[6] Eric R. Pianka, “On r- and K-Selection,” The American Naturalist 104, no. 940 (Nov. - Dec., 1970): 592-597.