ABSTRACT
Investigations of retrospective memory-memory for past events and experi ences-led researchers to hypothesize that memory is not a unitary construct. Instead, it is composed of several kinds of memory systems or processes that are used differentially depending on task demands (for reviews, see Baddeley, 1990; Richardson-Klavehn & Bjork, 1988; Schacter, Chiu, & Ochsner, 1993). For example, we use short-term, primary, or working memory to maintain or manipulate information in consciousness for brief periods of time (Baddeley, 1986; Waugh & Norman, 1965), whereas we use long-term or secondary mem ory to store information permanently (Atkinson & Shiffrin, 1968). Episodic memory enables us to keep track of personally experienced events according to the time and place of their occurrence; semantic memory stores knowledge without reference to spatiotemporal context (Tulving, 1972). Declarative memory is concerned with memory for facts-propositions that have truth value-whereas procedural memory involves memory for skills or action se quences (Squire, 1987). We can retrieve past experiences consciously through explicit memory processes or we can express our knowledge of the past im plicitly through changes in performance (Graf & Schacter, 1985).
