To many observers, the study of unconscious psychological processes is personality psychology's greatest contribution to scientific knowledge. Advances in science usually involve increments in the understanding of well-known phenomena (Kuhn, 1962). Discovering entirely new phenomena is rare. Unearthing new phenomena of importance to society at large is rarer still. Evidence that psychological experience can be shaped by forces of which we are unaware (e.g., Janet, 1889; Freud, 1900) was that rarest of cases in which the field produced startling findings that altered society's view of human nature.

Evidence of unconscious influences was surprising, of course, because of the obvious importance of conscious self-reflection in human affairs. The ability to reflect on the world, ourselves, and our very capacity for self-reflection is our species' most distinguishing characteristic. The obviousness of self reflective capabilities should not cause the personality psychologist to neglect a careful analysis of conscious experience. Subjective, private experience (Singer & Kolligian, 1987) is a critical phenomenon unto itself, and is a human capability that enables people to shape the nature of their life circumstances and to influence the course of their personal development (Bandura, 1997; Rychlak, 1997).

This chapter reviews developments in the study of unconscious processes and conscious experience. After a brief historical overview, we outline important conceptual distinctions among conscious and unconscious phenomena. We then focus on unconscious processes in personality functioning. As we will see, some unconscious processes involve motivated states of psychological defense.