What experimental evidence is there for the existence of multiple memory systems?

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Laura Kemp                Cognitive Psychology

What experimental evidence is there for the existence of multiple memory systems?

Memory forms an important part of cognitive psychology and has been of interest to numerous psychologists.  This essay is going to refer specifically to the information-processing model of memory and will discuss the experimental evidence that exists for multiple memory systems.

The multi-store model of memory was first developed by Atkinson and Shiffrin (1968) and Waugh and Norman (1965).  It comprises sensory stores, short term-store and long-term store to form a model of memory and information processing.  One component of the system is the sensory register, where our feature detection and pattern recognition processes produce a cognitive code that can be stored for a brief period.  The sensory storage does not depend on resource allocation, so the person does not need to pay attention to the stimuli, and the coding happens automatically.  The sensory register is thought to be modality specific, that is, part of the storage is auditory, part of the storage is devoted to visual stimuli, and other parts devoted to the other senses.

Sperling (1960) conducted many studies in the area of memory, specifically sensory storage. Sperling's main contribution has been to find a technique which has been called the partial report procedure. In one experiment he presented a matrix of 3 lines of four letters each to his subject for 50msec. Under partial report procedure a high, medium or low- pitched tone is produced at the same time as the presentation is over and the task given to the subject is to reproduce only the first, second or third line according to the pitch of the tone. A performance in the order of three correct responses was obtained under these conditions. Since the subject was unable to predict what line he would be asked to report, it must be acknowledged that immediately after the end of the presentation, the information necessary to recall the letters had to be available somewhere.

This led Sperling to the hypothesis that one form of presentation of the visual stimulation remains accessible for a short time after the presentation. It was Neisser (1967) who proposed that this representation should be called an icon.  Iconic storage was claimed to be useless by some psychologists.  Haber (1983) claimed it was irrelevant to normal perception, as he assumed that the icon was created at the offset of a visual stimulus, but it is actually created at its onset.  Therefore, even with a continuously changing visual world, iconic information is still useful.

The Echoic store is a transient auditory store, holding relatively unprocessed input.  It is similar to the iconic store except it refers to auditory rather than visual stimuli.  Treisman (1964) conducted experiments in this area and found that the temporal duration of unattended auditory information in echoic storage is about two seconds.

Short-term memory is another component of the multi-store model.  Our short-term memory is said to require the allocation of cognitive resources (Atkinson & Shiffrin 1968).  Peterson & Peterson (1959) conducted the classic study of short-term storage.  From their findings it could be assumed that the distractor task was preventing the subjects from performing rehearsal, and without this, that the information disappears.  Therefore Peterson & Peterson could assume that the retrieval failures were due to the decay of the information.  This study was an important one, as psychologists had known for a while that decay was not necessarily a major reason for retrieval failure over long intervals, (Jenkins & Dallenbach 1924).  Therefore with the evidence that decay was responsible for retrieval failures over short time periods, there was strong evidence for two different types of storages-short term store and long-term store, suggesting there must be a difference in the forgetting mechanisms of the two different types of memory.  The Petersons’ study was criticised by some, who said that they had not accounted for the concept of interference of earlier trials on later trials.  The Petersons defended themselves, saying that if this was the case, subjects’ performance should get worse on successive trials of the counting backwards distraction task.  Their argument was accepted until Keppel and Underwood (1962) studied the Peterson’s study closely and noticed that they had given subjects two practice trials.  When the study was replicated without the practice trials, a build up of interference occurred across the trials.  They could conclude that at least some interference could be involved in forgetting from short-term store.  Glanzer and Cunitz (1967) conducted a study that can be assumed to tie in with the Keppel and Underwood study.  They looked at a serial position curve, studying primacy and recency effects.  There was less interference at the start, and a greater amount at the end.  Their experiment is said to show decay in addition to interference.

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A major property of short-term memory is said to be the level of processing.  Craik and Tulving (1975) conducted a study from which they concluded that the level of processing during input affected recall.  They found that subjects remembered the words which had been presented with more complex sentences twice as well as the ones associated with less complex sentences.  In all cases semantic processing had been carried out, therefore there should have, in theory, been no difference in retrieval.  That is until you consider the nature of the elaborate rehearsal and the larger cognitive structure into which the elaborated code ...

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