Big Five is a popular system of personality categories that began as a list of words describing personality traits gathered from the dictionary. Mental symmetry is a cognitive meta-theory that began as a system of cognitive styles which models the mind as seven interacting cognitive modules. This paper uses mental symmetry to analyze Big Five from a cognitive perspective. In brief, four of the Big Five categories describe various aspects of emotional behavior that the average person would label as unusual, while the final category of Conscientiousness describes the mental circuit of technical thought as viewed from the perspective of the average person.