Psychological Science 21(6) 820 –828 © The Author(s) 2010 Reprints and permission:

Personality psychology promotes a systematic approach to understanding individual differences in behavior, emotion, motivation, and cognition, through the development of com-prehensive taxonomies of personality traits. However, these descriptive taxonomies have not typically been linked to empirical data from neuroscience research. Individual differ-ences are relevant to education and health, as well as basic science, and are therefore increasingly the focus of cognitive, affective, and social neuroscience research (Kosslyn et al., 2002). However, such efforts have not typically been system-atic or comprehensive. Personality neuroscience is emerging as a subdiscipline focused on testing and refining neurobio-logical theories of personality (Canli, 2008; DeYoung & Gray, 2009). In the study reported by this article, we used magnetic resonance imaging (MRI) to test a biological theory of the Big Five personality traits (DeYoung & Gray, 2009): Extraver