Personality and Dementia :

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.

Using a sample of 315 adult men and women, self-reports on Wiggins's revised Interpersonal Adjective Scales were jointly factored with self-reports, peer ratings, and spouse ratings on the NEO Personality Inventory to examine the relations between the two models. Results suggest that the interpersonal circumplex is defined by the two dimensions of Extraversion and Agreeableness, and that the circular ordering of variables is not an artifact of response biases or cognitive schemata. Circumplex and dimensional models appear to complement each other in describing the structure of personality, and both may be useful to social psychologists in understanding interpersonal behavior.