Define short-term memory and describe the main factors that influence the number of items recalled from short-term memory. Evaluate Nairne's theory relative to traditional theories, clearly stating your criteria for evaluation.

Define short-term memory and describe the main factors that influence the number of items recalled from short-term memory. Evaluate Nairne’s theory relative to traditional theories, clearly stating your criteria for evaluation.

Memory has always been an area of psychology to receive a great deal of attention. In 1890, William James [2], stated that there were two components to the human memory. He made the distinction between a ‘primary’ memory, now termed short-term memory and a secondary memory, now termed long-term memory. Eysenck and Keane (2002 [3]) state that the primary memory relates to information that remains in consciousness after it has been perceived and forms part of the psychological present. They then state that secondary memory contains information about events that have left consciousness and are therefore part of the psychological past (Eysenck and Keane 2002 [3]).

In the 1960’s a major debate surfaced about whether the short-term memory and long-term memory worked independently of each other or whether they were a part of the same unitary system. Many theories were developed on this basis and there is a great deal of evidence to support the fact that they work independently and have very separate functions. As a result of this debate, many researchers became interested in the concept of short-term memory. Through experimental evidence it became apparent that this system has a very limited capacity and that storage is very fragile due to the risk of forgetting. Baddeley (1999 [1]) stated that an important aspect of the short-term memory is the ability of the characteristics of the system that enable the holding and manipulation of limited amounts of information. It became apparent to him that to some extent short-term memory could apprehend momentary ideas that would otherwise go unnoticed, retain them, relate them and manipulate them for its own purposes. However, due to the limited capacity of short-term memory, the number of items that could be retained was also limited. The capacity of short-term memory has been assessed using the techniques of digit span and the recency effect in free recall (Eysenck and Keane 2002 [3]).

In the nineteenth century the capacity of immediate memory preoccupied a number of theorists (Baddeley 1999 [1]). Take for example the work of William Hamilton. He observed that if someone threw a handful of marbles on the floor, the maximum number to be perceived with reasonable accuracy would be about seven (Baddeley 1999 [1]). Influenced by Hamilton, Jacobs conducted the first systematic experiment on this idea (1887 [1]). He devised a technique known as ‘digit span’ that has been significantly used ever since. The study he developed involves presenting subjects with a sequence of digits, they are asked to repeat the digits back in the same order they appeared. The length of the sequence is increased until the point where the subject fails every time. The sequence length at which they are correct half the time becomes their digit span (Baddeley 1999 [1]). This number of digits is the limit to which one can perform on this task. The average digit span is six or seven, but there is a wide variation in performance; some can only manage as little as five digits whereas others can manage up to ten. In 1956, Miller supported this idea stating that roughly seven pieces of integrated information could be stored in the short-term memory. (Eysenck and Keane 2002 [3]). It came to light that if one speaks the sentences or sequences aloud they might perform more successfully. Baddeley (1999 [1]) states that ‘articulating and hearing the sounds of the numbers registers them in the brief echoic store’. This revelation indicates that rehearsal and repetition are key elements to a better performance and have a significant effect on the ability to recall, therefore increasing the digit span. Baddeley states that another way to enhance performance is to group the stimuli rhythmically. The role of rhythm has been neglected in the study of memory but proves to be a successful method. The rhythmic technique appears to reduce the chance of repeating the numbers in the wrong order (Baddeley 1999 [1]). Researchers have conducted studies into the grouping of stimuli and found that grouping in three’s appears to have the highest rate of success. This technique can be demonstrated using telephone numbers. It is evident that people remember telephone numbers with greater ease if they hear them broken down into groups of three or four digits (Baddeley 1999 [1]). Aitkin was a mathematician with amazing memory abilities. According to Baddeley (1999 [1]), he was able to recall the value of pi (the symbol for the ratio of the circumference of a circle to it’s diameter) to the one thousandth decimal place. Aitkin’s theory was to arrange the digits in rows of fifty, each containing ten groups of five digits. He then recited them again and again using a particular rhythm and they became easier for him to memorise (Aitkin 1937 [3]).

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A crucial element in Aitkin’s ability to recall such large numbers included the use of a process known as ‘chunking’. He was able to separate seven digits into a single ‘chunk’. Using a technique such as this meant that the short-term memory was now assessed on the number of chunks one could retain rather than how many numbers they could retain. This technique is most successful when attempting the recall of letters. It involves chunking letters together to make a single sound therefore reducing the amount of information that is stored allowing for more room in the short-term memory (Baddeley 1999 [1]). So far it is evident that digit span, verbal speech, rhythm and chunking all have an effect on the number if items that can be recalled from the short-term memory. Another factor affecting recall and used in the testing of short-term memory capacity limits is the recency effect in free recall. Free recall involves subjects being presented with a list of items to remember and requested to repeat them in any order. According to Eysenck and Keane (2002 [3]), the recency effect ‘refers to the finding that the last few items in a list are usually much better remembered in immediate recall that the items in the middle of the list’. Glazner and Cunitz (1966 [3]) stated that counting backwards for as little as ten seconds between the presentation of a list and the beginning of the recall task mainly affects the recency effect. Eysenck and Keane insist that this happens because of the two or three words that are susceptible to the recency effect being in the short-term store at the end of the presentation list making them vulnerable (2002 [3]). Bjork and Whitton (1974[3]), continued this line of research and found that if participants counted backwards for twelve seconds after each item in the list was presented, the recency effect remained. Baddeley proposed that the recency effect could be eradicated by simply adding a small amount of distraction, such as asking subjects to add five single digits. According to Glazner (1972 [1]), due to the apparent differences between the recall of recent and early items, there is a suggestion that the former depends on short-term memory and that the latter is more dependent on the longer term aspects of memory.

As previously mentioned, Baddeley considered that one of the important factors on recall from short-term memory involved speech. For Tehan and Lalor (2000 [6]) memory span is also affected by speech-based variables. In their article they explain how Baddeley paid close attention to the effects of such variables. In 1966, Baddeley devised a two-component structure to account for the interactive effects of these variables on memory span and recall. His first component was the rapidly decaying phonological store in which phonological representations are temporarily stored. The second component of his theory was the verbal rehearsal process consisting of the dual function of translating visual input into phonemic representations and maintaining these representations into a readily retrievable state. Baddeley stated that the rehearsal process became responsible for producing word length effects and that it was a limiting factor on performance. According to Tehan and Lalor (2000 [6]), there is substantial empirical support for the two-component theory shown in Baddeley et al’s demonstration in 1975 that memory span was in fact related to the spoken duration of words. The material words that took longer to pronounce were associated with a lower level of recall. Baddeley et al found a positive linear relationship existed between the number of items that could be recalled and the rate of rehearsal for particular material (Tehan and Lalor 2000 [6]). In 1992, Cowan [6] provided support for the work of Baddeley et al (1975 [6]); he found that there was a positive association between memory span and the duration of spoken recall. Cowan stated that more capable subjects responded at the same rate as subjects with lower memory spans but responses continued for longer periods. Cowan argues that pause times in-between the words reflects retrieval and reactivation efficiency. In other words, subjects are assumed to retrieve and refresh the unrecalled items from the short-term memory. With spoken recall studies such as those conducted by Cowan and Baddeley, items are subject to rapid decay during recall. Items in the short-term store are therefore at the risk of being forgotten before the recall task begins, mainly due to their fragile state in such a limited store.

Various theorists such as Ebbinghaus (1885/1913 [3]) have argued that forgetting occurs because of a spontaneous decay in memory traces over time. Eysenck and Keane note that the main assumption is that forgetting depends on the length of the retention rather than on what happens between the learning and the test. In the late fifties, John Brown (1958) in the United Kingdom and the Petersons (1959) in the United States investigated short-term forgetting. Results of their studies showed that even sequences within the memory span would show clear forgetting if the subject was prevented from thinking about the stimuli or rehearsing it in anyway (Baddeley 1999 [1]). Peterson and Peterson (1959 [1,3]) conducted their experiment using sequences of three unrelated consonants. They presented the stimuli to their subjects and immediately after the subject had read them, they were shown a three-figure number and asked to start counting backwards from it in threes. After a period of time ranging from three to eighteen seconds, the subject was then asked to recall the original three-letter stimulus. The task was repeated three times, each time followed by a counting task and then a recall test. Peterson and Peterson (1959 [1]) put the results into a line graph for the times they prevented their participants from rehearsing the items and for the interval periods from three to eighteen seconds, the line formed was named as the ‘forgetting curve’. It was evident that the forgetting curve was the same whether one was trying to remember three letters or three words (Baddeley 1999 [1]). Baddeley points out that nevertheless, single three letter words show very little forgetting. This indicates that, as with memory span, the important fact is the number of chunks remembered rather than the number of letters (Baddeley 1999 [1]). The research presented has demonstrated that many factors have an effect on the number of items to be recalled from the short-term memory. It is clear that the two highlighted factors are the digit span and the recency effect. Many researchers have exposed other variables as being responsible factors on the amount to be recalled from short-term memory. Highlighted in this research are the factors of chunking, rhythm, spoken recall and decay. Many of these ideas contribute to an understanding of how performance in recall testing can be enhanced but also how one may forget things over the short-term. The components of decay and rehearsal are said to build the ‘standard’ model of memory. Nairne (2002 [5]) is one of a few researchers to refute the standard model. His study is based on remembering over the short term and proposes an opposing theory to that of the standard model.

Information within the human memory needs to be accessible in some form. Many theorists believe the temporary store in short-term memory to be the holding bay for information. Nairne concludes that many believe the ‘activation’ of knowledge enables individuals to remember over the short term, such activation establishes an activity trace in the short-term memory enabling one to recall pieces of information (Nairne 2002 [5]). With a process such as this it is assumed that activation decays spontaneously over time. This would mean another process such as rehearsal is needed to maintain the availability of information. As mentioned above, Nairne considers the main components of the standard model to be activation, rehearsal and decay. McAlree (1998 [5]) believes that once items are activated they exist in a state of immediate accessibility, stating that the amount of activation in turn, accrues from a continual trade-off between rehearsal and decay (Nairne 2002 [5]). Nairne states that the case for the standard model has lost much of its support over the past decade. He clearly defines the fact that remembering is always a joint function of trace properties and retrieval cues, if this is the case, it would not make sense that a single property such as ‘activation’ can be identical to remembering (Nairne 2002 [5]). More researchers are beginning to recognise the fact that the retention of information in short-term memory is cue driven, as is the retention of information in long-term memory. Nairne believes that simple appeals to rehearsal or decay are unlikely to explain the specific details of short-term forgetting (Nairne 2002 [5]). He criticises the view that rehearsal and decay are determining factors of remembering over the short term and opts for a cue driven approach. He concludes that it seems likely rehearsal could be a mechanism for representation of stimulus material, meaning that discrete rehearsals might replicate items in memory that enhance the memory later (Nairne 2002 [5]). Nairne regards the most important aspect of rehearsal is that it produces benefits, not in the sense that it refreshes a decaying trace but because it promotes the idea that short term memory uses a cue-driven retrieval process (2002 [5]). He then assessed the role of decay in short term remembering. Decay is rarely used to explain the process of memory; it only becomes useful in the theories of short-term memory. His view on decay is a lot higher than that of rehearsal; he is able to accept that the role of decay has importance. This is due to the fact that it fits into the assumption of the standard model that activation is lost in a second or two and must be refreshed some how. Nairne identifies the link between remembering and activation in the standard model, with no reference to retrieval cues. Baddeley (1990 [5]) argued for the recognition of decay and rehearsal and stated that they could both be operating in the short-term memory. It is evident that Nairne does actually accept the importance of the roles of decay and rehearsal, however, he does not rely on them as far as remembering over the short term is concerned. One of the major issues to overcome for many theorists was the proposal that remembering over the short term is actually cue driven.

Nairne began to evaluate alternative models to the standard model. Nairne is aware that many factors have influenced the shift towards a cue-driven understanding of remembering in the short-term. Wickens (1970 [5]) devised a ‘Prototypical Paradigm’ to test immediate memory. His experiment involved subjects receiving immediate memory trials where successive lists were drawn from the same conceptual class, for example animals. Wickens found that performance would typically decline over the trials; he stated that this was a result of people using the conceptual class as a cue to guide short-term recall. According to Watkins and Watkins (1975 [5]) the effectiveness of the cue is determined by the degree of cue overload. Nairne (2002 [5]) concludes that on build up trials, the cue becomes overloaded and the performance suffers but on release trials, the conceptual cue specifies the items on the correct trial and performance improves. Nairne’s interest in the idea of cue dependent retrieval processes in remembering led to the development of his own model. He referred to it as a ‘unitary’ model due to the fact that assumes similar processes for short and long-term remembering (2001 [5]). In 1988, Nairne devised the ‘Feature Model’. Nairne believed the information stored in short-term memory is not an activated ‘item’ ready for retrieval, but an arrangement of activated cues that are reconstructed moments before retrieval. For Nairne, the cues in his feature model consist of previous records, for example, records of a just presented list that have deteriorated through interference would be present. He believes the process of retrieval consists of the item for recall being selected from the long-term memory. He states that it ‘is not the match between the to-be interpreted cues and long-term memory candidates that is important but how well cues specify one or more of the targets (Nairne 2001 [5]). For Nairne, short-term forgetting in this model occurs because the available cues become poor predictors of target items. The models proposed by Nairne and Wickens are two examples of how remembering over the short-term is assumed to be primarily cue driven towards performance in come cases.

It is evident that Nairne considers activation, rehearsal and decay to have an important role in remembering over the short-term. Throughout his article he also makes reference to the factors affecting recall such as digit span and the word length effect. As research progresses, new ideas are developed and researched. Long-term memory has always been specified as being cue-driven; it is therefore acceptable that the same idea could be applied to short-term memory. Nairne’s theory is successful in developing the new idea of the involvement of cues in remembering. There is much research to show that theories and ideas regarding short-term memory are becoming more and more advanced. Baddeley has been a key researcher in the work on short-term memory and has helped to advance the discussion. Nairne’s theory supports the standard model to some extent, he has accepted it and agrees with models that incorporate it’s basic ideas. There is agreement about the fact that many factors have an effect on the amount of information one can recall from short-term memory, the only real dispute among researchers is remembering over the short term and whether or not models should be formed on a cue-driven basis.

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Teacher Reviews

Here's what a teacher thought of this essay

Linda Penn

7th of Aug 2013

Summary The writer has made a valid attempt at this essay including many references. There appears to be a clear understanding of the arguments surrounding the standard model and Nairne's cue driven model for the short term memory. However, this essay would have scored even higher if it had been written in the writer's own words. Also, some of the basic concepts should have been explained briefly, but concisely, instead of bypassing them altogether. Explaining these shows that the writer understands the work. Star rating 4*

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