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Key Words short-term memory, rehearsal, decay, activation, working memory
* Abstract Psychologists often assume that short-term storage is synonymous with activation, a mnemonic property that keeps information in an immediately accessible form. Permanent knowledge is activated, as a result of on-line cognitive processing, and an activity trace is established "in" short-term (or working) memory. Activation is assumed to decay spontaneously with the passage of time, so a refreshing process-- rehearsal-is needed to maintain availability. Most of the phenomena of immediate retention, such as capacity limitations and word length effects, are assumed to arise from trade-offs between rehearsal and decay. This "standard model" of how we remember over the short-term still enjoys considerable popularity, although recent research questions most of its main assumptions. In this chapter I review the recent research and identify the empirical and conceptual problems that plague traditional conceptions of short-term memory. Increasingly, researchers are recognizing that short-term retention is cue driven, much like long-term memory, and that neither rehearsal nor decay is likely to explain the particulars of short-term forgetting.
INTRODUCTION
How do we remember over the short term? It is clearly adaptive to keep recent information available in some kind of accessible form. It would be difficult to comprehend spoken language, which occurs sequentially, or read any kind of text without remembering the early part of an utterance or the themes relevant to a passage. Virtually all complex cognitive activities-reading, reasoning, problemsolving-require access to intermediate steps (as in adding or multiplying two-- digit numbers in the head) or other situation-specific information (Baddeley 1992, Kintsch & VanDijk 1978). What then are the psychological mechanisms, or systems, that drive and control such short-term maintenance?
For many years psychologists have essentially agreed about the main mechanism controlling the temporary storage of information. The generally accepted view-referred to here as the standard model-is that short-term storage arises from activation, a mnemonic property that keeps information in an immediately accessible form. Permanent knowledge is activated, as a byproduct of on-line cognitive processing, and comes to reside "in" short-term (or working) memory. Short-term memory, as a whole, is simply defined as the collective set of this activated information in memory (e.g., Cowan 1995, Shiffrin 1999). Activation is assumed to be fragile, however, and it can...