Perceptual Representation Systems and Implicit Memory

Consider the following experimental situations. In the first, subjects are shown a list of familiar words and are instructed to carefully study each of them. After performing a variety of unrelated tasks for several minutes, they are told to think back to the study list and recall as many of the presented words as possible. Subjects are then shown a series of words-half were presented in the study list, half were not-and are instructed to say “yes” if they remember having studied the items, and “no” if they do not remember them. In the second situation, subjects also study a word list and then engage in unrelated activities for a few minutes. However, instead of then being asked to remember previously studied items, the subjects are asked to write down the first word that comes to mind in response to a series of 3-letter word stems; some can be completed with previously studied words, and some cannot. The first of these two hypothetical situations reflects the way in which cognitive psychologists have traditionally studied human memory: by assessing subjects’ intentional or explicit memoy for information acquired during a study episode with standard recall and recognition tests. In the second situation, memory is inferred from an enhanced tendency to complete 3-letter stems with previously studied words; this is often referred to as “repetition priming” or “direct priming” (cf., Cofer, 1967; Tulving & Schacter, 1990). Priming effects need not and often do not involve any conscious or explicit recollection of a prior episode, and thus can be said to reflect implicit memory for previously studied information (Graf & Schacter, 1985; Schacter, 1987). Priming has been assessed with a variety of implicit memory tasks that do not require explicit recollection of a specific prior episode. One common type of implicit test involves completing word stems or word fragments with the first word that comes to mind, as in the foregoing example (e.g., Graf & Mandler, 1984; Light, Singh & Capps, 1986; Roediger & Blaxton, 1987a, b; Schacter & Graf, 1986a, b; Tulving, Schacter & Stark, 1982). Another frequently used implicit task involves word identification: Subjects are required to try to identify a word from a brief (e.g., 50-msec) perceptual exposure, and priming is indicated by more accurate identification of a recently studied item than of a new, nonstudied item (e.g., Jacoby, 1983a, b;