1. the position that mind and body are distinct, incompatible substances that nevertheless interact, so that each has a causal influence on the other. This position is particularly associated with René Descartes. See Cartesian dualism; mind–body problem.

2. a set of approaches, particularly in personality psychology, in which behavior is explained not in terms of personality attributes or situational influences but by references to interactions that typify the behavior of a certain type of person in a certain type of setting. —interactionist adj.