radex theory of intelligence
a psychometric theory of intelligence postulating that the organization of mental abilities forms a radial order of complexity (or radex). The radex comprises two parts: (a) a simplex, which is the relative distance from the center of a circle, with abilities that are closer to the center of the circle therefore being closer to the construct of general intelligence, which is at dead center; and (b) a circumplex, which is the relative distance around the circle, with abilities that are more highly correlated therefore being located closer to each other. Thus the system identifies abilities through a set of polar coordinates (rather than the Cartesian coordinates used by other systems). [proposed by U.S. psychologist Louis Guttman (1916–1997)]