Psychological investigations of human memory have traditionally been concerned with conscious recollection or explicit memory for specific facts and episodes. Since the 1980s, however, there has been growing interest among the scientific community in a nonconscious form of memory, referred to as implicit memory (Roediger and McDermott, 1993; Schacter, 1987; Toth, 2000). Implicit memory does not require any explicit recollection of specific episodes. Recent experimental investigations have revealed dramatic differences between implicit and explicit memory, and these differences have had a major impact on psychological theories of the processes and systems involved in human memory.

To understand the nature and significance of implicit memory, it is necessary first to consider the types of experimental paradigms that are used to assess both explicit and implicit memory. In a traditional explicit memory paradigm, there are three main phases: a study episode in which people are exposed to a set of target...