The neuroanatomical delineation of agentic and affiliative extraversion

Abstract

Extraversion is a fascinating personality dimension that consists of two major components, agentic extraversion and affiliative extraversion. Agentic extraversion involves incentive motivation and is expressed as a tendency toward assertiveness, persistence, and achievement. Affiliative extraversion involves the positive emotion of social warmth and is expressed as a tendency toward amicability, gregariousness, and affection. Here we investigate the neuroanatomical correlates of the personality traits of agentic and affiliative extraversion using the Multidimensional Personality Questionnaire Brief Form, structural magnetic resonance imaging, and voxel-based morphometry in a sample of 83 healthy adult volunteers. We found that trait agentic extraversion and trait affiliative extraversion were each positively associated with the volume of the medial orbitofrontal cortex bilaterally (t's ≥ 2.03, r's ≥ .23, p's < .05). Agentic extraversion was specifically and positively related to the volume of the left parahippocampal gyrus (t = 4.08, r = .21, p < .05), left cingulate gyrus (t = 4.75, r = .28, p < .05), left caudate (t = 4.29, r = .24, p < .05), and left precentral gyrus (t = 4.00, r = .18, p < .05) in males and females, and the volume of the right nucleus accumbens in males (t = 2.92, r = .20, p < .05). Trait affiliative extraversion was not found to be associated with additional regions beyond the medial orbitofrontal cortex. The findings provide the first evidence of a neuroanatomical dissociation between the personality traits of agentic and affiliative extraversion in healthy adults.

Figure 1

Social Potency ROI Results ROI regions showing significant increases in gray matter in participants with higher SP scores. The left side shows significant gray matter clusters in ROI regions related to social potency. The right side shows scatterplots displaying the correlations between the social potency score (x-axis) against the ROI-scaled gray matter values (y-axis). Medial orbitofrontal cortex correlations were significant at p < 0.01, and the right nucleus accumbens correlation was significant at p < 0.05

Figure 2

Social Potency Whole brain VBM Results Whole brain VBM analysis of gray matter regions associated with social potency. The left parahippocampal gyrus, left cingulate gyrus, left caudate, and left precentral gyrus were significantly correlated with social potency when correcting for multiple comparisons. The colored bar represents t-scores from 0 to 5. See table 3 for coordinates.

Figure 3

Social Closeness ROI Results ROI regions showing significant increases in gray matter in participants with higher social closeness scores. The left side shows significant gray matter clusters in ROI regions related to social closeness. The right side shows scatterplots displaying the correlation between the social closeness score (x-axis) against the ROI-scaled gray matter values (y-axis). All correlations were significant at p < 0.05.

Figure 4

Social Closeness Whole Brain VBM Results Whole brain VBM analysis of gray matter regions correlated with social closeness. No regions survived correction for multiple comparisons. The colored bar represents t-scores from 0 to 5. See table 3 for more information.