On the quest for the neural correlates of personality : A systematic review on the state-of-the-art neuroscience on the Big Five factors

Abstract

Personality is among the most empirically investigated concepts within psychology yet, to a large extent, unexplored by modern neuroscience. This is despite the fact that the Five-Factor Model of personality (FFM: neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness), a general statistical synthesis of the diverse psychological factors related to personality and individual differences, has been the consensus within psychology since late 20th century. The purpose of this systematic review was to explore the concurrent evidence on the neural correlates of personality as revealed by an extensive array of state-of-the-art neuroscience methodologies, and to point out the most fruitful pathways for further research in the field of personality neuroscience.

Utilizing the PRISMA-framework for systematic reviews (Page et al., 2021), a literature search on the neuroscientific evidence published after the year 1999 in the most relevant databases in the field of psychology (PsycINFO, PsycArticles, and MEDLINE) was conducted individually on each of the FFM factors, including their relevant facets as defined in the NEO-PI-R (Costa, 1992). A variety of neuroscience methods were included, from structural and functional neuroimaging to electrophysiology, non-invasive neural stimulation, as well as relevant clinical studies. The search was targeted to studies with a large enough, adult sample (n ≥ 50), in addition to a reported significant correlation to a personality measure. The initial searches yielded altogether 766 articles, and, after the systematic, two-level screening and selection process, there were altogether 77 unique studies eligible for the review: 29 studies reported results on more than one trait, 22 on Neuroticism (N), 8 on Extraversion (E), 5 on Agreeableness (A), 4 on Conscientiousness (C), and 9 on Openness (O). The average sample size of the studies in this review was around 301 (50—3 112), and the median 130.

The FFM traits with the most research evidence collected on so far were neuroticism and extraversion. The neuroscience methods were differentially employed in the research of the different FFM traits. The results implicate that the different FFM traits and their sub-facets are based on neural systems that are differently emphasized on the levels of structural (e.g., neuroticism on the more limbic/subcortical versus conscientiousness and openness on the prefrontal cortical level) and functional neuroanatomy (e.g., the lack of default mode network functional connectivity in openness), as well as neurotransmission (e.g., dopamine as more prominent in extraversion and serotonin in neuroticism). Openness arose as a trait more neuroscientifically relevant than previously thought based on the number of single-trait studies, specifically thanks to the novel statistical methodologies of network neuroscience.

All in all, the FFM traits would seem to engage large-scale networks and complex patterns of interactions across different neurobiological systems, and the challenge of future personality neuroscience is to further outline each of the specific trait networks and their interactions on a neurobiological level. The limitations of this single-author systematic review on the significant neural correlates of the FFM are discussed, and in conclusion, the review provides a collective discussion of the relevant theoretical and methodological pathways for further research in personality neuroscience. It would seem personality neuroscience is truly a field with prospects brighter than ever and, along with the latest methodological developments, great advancement in the field can be expected in the coming years.