Implicit memory: a selective review.

The investigation of human mcmory has undergone a major transformation during the past decade, characterized by Richardson-Klavehn & Bjork (1988) as a "revolution in the way that we measure and interpret the influence of past events on current experience and behavior ̄.." (pp. 476-77). It is not clear whether this transformation should be viewed as paradigm shift, as Kuhn (1962) suggested, or, more modestly, as the emergence of a new subarea of research. What does seem clear, however, is that the "revolution" has already yielded, and will continue to yield, an outpouring of new data and ideas concerning the nature of memory. The scientific substance of this revolution turns on a distinction between two different ways in which memory for prior experiences can be expressed, most frequently referred to as explicit and implicit memory, respectively (Graf& Schacter 1985; Schacter 1987). Explicit memory entails intentional or conscious recollection of previous experiences. In a typical explicit memory experiment, subjects are initially shown a series of words, pictures, or some other set of to-be-remembered materials. Later, they are given a recall or recognition test, in which they must think back to the study episode in order to produce or select a correct response. The vast majority of studies on human memory have, until recently, conformed to this paradigm; theoretical ideas about memory have, with few exceptions, addressed explicit remembering. Implicit memory, by contrast, entails a facilitation or change in test performance that is attributable to infor-