When I was 17, I was introduced to the idea of ‘personality’ as a serious psychological concept, starting with extroversion/introversion. I did not believe a word of it – I memorized it – gave it back on the exams – but never believed it. Ever since personality has been in the ‘maybe, but probably not’ category or even the ‘who cares?’ category. I do think that people have patterns of thought and behaviour. People are somewhat predictable. But I cannot see these individual patterns as a very few clear patterns (16 or 4 or 5). Nor can I see them as unchanging in any individual. And most importantly, I do not see them as deep, fundamental, differences in how the brain is built or how it operates. I will try to be more open-minded (but with reservations).
Now there is a paper (see citation) that attempts to show differences between the personality types in the ‘big5′ list using the connectivity between brain areas in resting state fMRI. Here is the abstract:
Personality describes persistent human behavioral responses to broad classes of environmental stimuli. Investigating how personality traits are reflected in the brain’s functional architecture is challenging, in part due to the difficulty of designing appropriate task probes. Resting-state functional connectivity (RSFC) can detect intrinsic activation patterns without relying on any specific task. Here we use RSFC to investigate the neural correlates of the five-factor personality domains. Based on seed regions placed within two cognitive and affective ‘hubs’ in the brain—the anterior cingulate and precuneus—each domain of personality predicted RSFC with a unique pattern of brain regions. These patterns corresponded with functional subdivisions responsible for cognitive and affective processing such as motivation, empathy and future-oriented thinking. Neuroticism and Extraversion, the two most widely studied of the five constructs, predicted connectivity between seed regions and the dorsomedial prefrontal cortex and lateral paralimbic regions, respectively. These areas are associated with emotional regulation, self-evaluation and reward, consistent with the trait qualities. Personality traits were mostly associated with functional connections that were inconsistently present across participants. This suggests that although a fundamental, core functional architecture is preserved across individuals, variable connections outside of that core encompass the inter-individual differences in personality that motivate diverse responses.
So the general plan seems to be (1) assign personality categories to the subjects using questionaire (2) predict the brain areas that will have connectivity increased for each personality category (3) pick ‘hubs’ that should be connected to the areas of interest and show the extent of connection of each area to the hubs (4) compare connectivity with prediction.
This is a similar plan to the one used by one of the authors, DeYoung, in 2010 to try and show areas that were larger/smaller could be predicted by personality categories. Again the abstract:
We used a new theory of the biological basis of the Big Five personality traits to generate hypotheses about the association of each trait with the volume of different brain regions. Controlling for age, sex, and whole-brain volume, results from structural magnetic resonance imaging of 116 healthy adults supported our hypotheses for four of the five traits: Extraversion, Neuroticism, Agreeableness, and Conscientiousness. Extraversion covaried with volume of medial orbitofrontal cortex, a brain region involved in processing reward information. Neuroticism covaried with volume of brain regions associated with threat, punishment, and negative affect. Agreeableness covaried with volume in regions that process information about the intentions and mental states of other individuals. Conscientiousness covaried with volume in lateral prefrontal cortex, a region involved in planning and the voluntary control of behavior. These findings support our biologically based, explanatory model of the Big Five and demonstrate the potential of personality neuroscience (i.e., the systematic study of individual differences in personality using neuroscience methods) as a discipline.
I still find the idea of 5 distinct personality traits, frankly, simplistic. It is way too neat and tidy for a complex biological system. However, the group is going about their research in a logical way, so that if personality types (or something similar) are a part of a deep and fundamental aspect of peoples’ thought and behavior, they may show it convincingly. They call their quest ‘personality neuroscience’ – at least they are going for real evidence.
Adelstein, J., Shehzad, Z., Mennes, M., DeYoung, C., Zuo, X., Kelly, C., Margulies, D., Bloomfield, A., Gray, J., Castellanos, F., & Milham, M. (2011). Personality Is Reflected in the Brain’s Intrinsic Functional Architecture PLoS ONE, 6 (11) DOI: 10.1371/journal.pone.0027633
DeYoung, C., Hirsh, J., Shane, M., Papademetris, X., Rajeevan, N., & Gray, J. (2010). Testing Predictions From Personality Neuroscience: Brain Structure and the Big Five Psychological Science, 21 (6), 820-828 DOI: 10.1177/0956797610370159