Little Evidence for Associations Between the Big Five Personality Traits and Variability in Brain Gray or White Matter

Attempts to link the Big Five personality traits of Openness-to-Experience, Conscientiousness, Extraversion, Agreeableness, and Neuroticism with variability in trait-like features of brain structure have produced inconsistent results. Small sample sizes and heterogeneous methodology have been suspected in driving these inconsistencies. Here, we tested for associations between the Big Five personality traits and multiple measures of brain structure using data from 1,107 university students (636 women, mean age 19.69±1.24 years) representing the largest attempt to date. In addition to replication analyses based on a prior study, we conducted exploratory whole-brain analyses. Four supplementary analyses were also conducted to examine 1) possible associations with lower-order facets of personality; 2) modulatory effects of sex; 3) effect of controlling for non-target personality traits; and 4) parcellation scheme effects. The analyses failed to identify any significant associations between the Big Five personality traits and variability in measures of cortical thickness, surface area, subcortical volume, or white matter microstructural integrity, except for an association between greater surface area of the superior temporal gyrus and lower scores on conscientiousness that explained 0.44% of the morphometric measure’s variance. Notably however, the latter association is largely not supported by previous studies. The supplementary analyses mirrored these largely null findings, suggesting they were not substantively biased by our choice of analytic model. Collectively, these results indicate that if there are direct associations between the Big Five personality traits and variability in brain structure, they are of likely very small effect sizes and will require very large samples for reliable detection.