Fundamental to a memory model is the ability to represent the ways in which information is stored. Human memory can be observed to store for the short term (a few seconds) and for the long term (many decades).


Short-term conscious memory is like a puff of smoke that spreads into thin air. As an empirical study of short-term memory, a test was reported by Peterson and Peterson in 1959. Subjects were told a set of three consonants, such as RLZ. After a delay of a few seconds they were asked to recall the consonants. Rehearsal, that is, being allowed to say RLZ over and over again, was discouraged in an attempt to discount long-term memory. The method of discouraging rehearsal was to ask the subject to count backward in steps of three from a given three-digit number, for example, 701, 689, 686, ..., immediately after being read the consonants. Under these conditions, it was observed that there was little recall after a few seconds, as shown in Figure B-1.

There is an obvious short-term memory loss in which detail fades away quickly. In this experiment, counting backward was observed to shorten the duration in which detail was remembered. A factor concerning fading may be that it is accelerated by the imposition of new impressions, that is, by interference. This suggests the possibility that interference either sooner or later is the normal way in which a short-term memory impression is terminated. The curve in Figure ...

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