Implicit memory: History and current status.

Memory for a recent event can be expressed explicitly, as conscious recollection, or implicitly, as a facilitation of test performance without conscious recollection. A growing number of recent studies have been concerned with implicit memory and its relation to explicit memory. This article presents an historical survey of observations concerning implicit memory, reviews the findings of contemporary experimental research, and delineates the strengths and weaknesses of alternative theoretical accounts of implicit memory. It is argued that dissociations between implicit and explicit memory have been documented across numerous tasks and subject populations, represent an important challenge for research and theory, and should be viewed in the context of other dissociations between implicit and explicit expressions of knowledge that have been documented in recent cognitive and neuropsychological research. Psychological studies of memory have traditionally relied on tests such as free recall, cued recall, and recognition. A prominent feature of these tests is that they make explicit reference to, and require conscious recollection of, a specific learning episode. During the past several years, however, increasing attention has been paid to experimental situations in which information that was encoded during a particular episode is subsequently expressed without conscious or deliberate recollection. Instead of being asked to try to remember recently presented information, subjects are simply required to perform a task, such as completing a graphemic fragment of a word, indicating