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Individual Differences in the Brain: Psychoticism

In the first two posts of this series, we already discussed Eysenck’s Big Three personality theory from the biological perspective. His theory stated that there are individual differences in the brain, which can be linked to three personality dimensions, namely extraversionneuroticism, and psychoticism. In the previous post, we focused on the individual differences regarding neuroticism. Today, we will focus on Eysenck’s final personality trait: psychoticism.

Eysenck’s Big Three: Psychoticism

We might need to do some explaining regarding the term psychoticism – extraversion and neuroticism are after all the more popular, widely accepted and used personality traits. Psychoticism is not as “popular” as the others terms. Yet why this is the case, will become clear soon enough.

The most important struggle with psychoticism? Definitely how to define it. Initially, psychoticism was seen as a broad dimension that covered all kinds of psychotic illnesses, such as schizophrenia, psychosis and bipolar disorder. However, from 1991 onwards, Eysenck started to use a definition that narrowed the term down. Rather than including all sorts of psychotic illness, he started to focus on the “asocial” side of psychoticism. Eysenck included asocial behaviours (e.g. aggressiveness, impulsivity, and lack of conformity) in his description in particular. Despite his focus on asocial behaviour, he did not exclude the links with psychosis. As a result, psychotic illnesses still play a part in the definition of psychoticism.

As we will notice, the struggle to establish a clear-cut definition of psychoticism affects the validation of the dimension and how much we know about it to this day.

The psychotic vs. non-psychotic brain

Thus Eysenck viewed the dimension of psychoticism as ranging from “asocial- and psychotic behaviours” to “highly socialized”. How did he think that individual differences in socialization were visible in our brains? In short, Eysenck suggested that psychoticism is associated with the amount of dopamine that is produced in our brains.
Eysenck reasoned that individuals with higher levels of dopamine production, and especially excessive amounts of dopamine production, receive more neural impulses that are difficult to inhibit. When we are lucky (and we are, most of the time!) our brains are wise enough to evaluate whether it is a smart move to engage in an impulse or not. However, if the brain receives many impulses, it is difficult to keep this up. Eysenck argued therefore that asocial behaviours are more likely to occur when the brain has difficulty inhibiting all the dopamine-induced neural impulses that it receives.

Was Eysenck right regarding psychoticism?

Does it make sense to suggest that an dopamine surplus in the brain is associated with more asocial behaviours? So far, a few studies have indeed associated levels of psychoticism with the binding and production of dopamine in the brain. These findings are in line with what Eysenck proposed: individuals with high levels of psychoticism appear to have a hyper-responsive dopamine system.

However, research on psychoticism tends to be scarce – especially when we compare it to the amount of research done on extraversion and neuroticism. This is mostly due to the fact that there is no clear-cut definition of psychoticism. As a result, the studies that do examine psychoticism, define the dimension differently and measure it in different ways. This in turn makes it difficult to compare results across studies and draw solid conclusions. It is a shame if you start to think about how much is still unknown about psychoticism, and how much knowledge we could still gain.

Creative geniuses

It is also a shame that the dimension of psychoticism tends to be viewed as an overall “bad thing”. That might be a surprising statement because, in general, humans do not prefer to be described as “asocial”. However, research suggests that there actually might be benefits related to some levels of psychoticism. Namely, it would appear that individuals with higher levels of psychoticism also tend to be more creative. As a result, they show superior performance in tasks that do not require effortful control. The root for this link between psychoticism and creativity can probably also be found in the dopamine system.

If you think about it, this link does make some sense. Many famous, creative artists are known for having some “odd” behaviours or ways of thinking that do not always fit with what society expects. So perhaps if you dream of becoming a big star… you might want to check your psychoticism levels?

If you would need to define psychoticism, how would you do this? What would you like to study and learn about psychoticism? Leave a comment below!

If you are interested in reading the literature used for this post, references and links are provided here:

Corr, P. J. (2010). The psychoticism–psychopathy continuum: A neuropsychological model of core deficits. Personality and Individual Differences48(6), 695-703.

Eysenck, H. (2006). The Biological Basis of Personality. New York: Routledge.

Mitchell, R. L., & Kumari, V. (2016). Hans Eysenck’s interface between the brain and personality: Modern evidence on the cognitive neuroscience of personality. Personality and Individual Differences103, 74-81.

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