The short-term memory (MCT) makes it possible to retain and re-use a quantity limited of information during a few seconds. A great number of research in cognitive Psychologie sought to determine the characteristics (capacity, duration, operation) and the role of the short-term memory in the Cognition.

Introduction and history

The short-term memory is not a new concept in psychology. William James in his Principles off psychology (1890) distinguishes already what it calls the primary memory of the secondary memory. This primary memory would be able to retain a small number of information, immediately present at the spirit, whereas the secondary memory contains a practically unlimited number of knowledge which however requires an effort to be recalled.

At the same time of other researchers are also worried memory, the first of which Hermann Ebbinghaus which is often quoted like the first psychologist to have shown the possibility of the experimental study of the memory. English Galton also considers to him that there exists a kind of short-term memory, related to the experiment conscious of the mental activity:

There seems to Be has short presence-chamber in my mind where full consciousness holds, and where two gold three ideas are At the same time in audience, and year handle-chamber full off more gold less allied ideas, which is situated just beyond the full ken off consciousness, Out off this handle-chamber the ideas most nearly allied to those in the presence chamber appear to Be summoned in has mechanically logical way, and to cuts to their turn off goes down for hearing.

During the twentieth century, the study of the memory will be somewhat left in sleep, particularly in the American universities dominated by the Béhaviorisme. At the time the scientific study of the cognitive processes is considered impossible and the psychologists concentrate for the majority on the observation of the behavior. The phenomena concerned with the memory are gathered under the label Apprentissage while taking care well not to evoke all mental Représentation intermediate between the stimulus and the associated answer. Certain researchers as Bartlett however makes exception in this landscape but they occupy more long-term Mémoire that of short-term memory.

With the beginning of the year 1960, whereas the cognitive Révolution takes form, the interest for the memory increases and an important debate opposes the partisans of a unit memory to holding of the existence of two distinct systems. If the American school represented by Melton account still today some faithful consensus seems to be established in favor of the existence of the short-term memory.

These experimental results are theorized by Atkinson and Schiffrin in their modal Modèle of the memory. The short-term memory is one of the essential components of this model and acts like an anteroom towards the long-term memory. Indeed, the probability of long-term memorizing depends in this model on the time spent in short-term memory.

Experimental evidence of the existence of the MCT

Several types of evidence are advanced in favor of the existence of the short-term memory. Most important are the existence of the effect of récence, the form of coding in short-term memory, the results with the tasks of empan mnemic and the specific disorders of certain cérébrolésés patients.

Effect of récence

The effect of récence indicates the facility to point out the last elements of a list of stimuli. Postman & Philips (1975) and Glanzer & Cunitz (1966) presented lists of words different length then required on their subjects to point out the words which they remembered in the order that they wished (free recall). When the recall takes place immediately the first and the last elements of the list are likely the most to be recalled while few subjects remember the medium the list. When the recall takes place after 15 or 30 seconds, only the elements of the beginning of the list have a strong probability of recall.

The authors interpret these experiments like a proof of the existence of a short-term memory ( shorts-term blind ) responsible for the effect of récence. Whereas the beginning of the list would be pointed out long-term memory (effect of primacy) and thus still available after 30 seconds, the end of the list would be stored in short-term memory and disappears quickly after the presentation.

See also: Effect of récence

Form coding in MCT

Another empirical argument in favor of the existence of the short-term memory is the difference of the form of coding of information in this short-term memory and in long-term memory. Conrad and Hull (1964) thus showed that coding in short-term memory is of phonological nature. The described experiment consists in requiring on subjects to memorize then to point out sequences of letters corresponding to phone numbers. It is noted that the most frequent errors are confusions between letters with the similar pronunciation (B and V for example) even if the stimuli are presented in visual form (i.e. the letters read are re-coded in acoustic form).

In two articles published in 1966, Baddeley compares the performances of short-term and long-term memorizing of four types of lists of words. The first type of list makes up of words phonologiquement close ( mad, man, course, edge, map ) but semantically without report/ratio. The second type of list contrary in made up to dissimilar words on the phonological level ( PEN, day, rig, bar, sup ). The third type of list is composed of semantically close words ( big, huge, great, length, tall ) whereas the fourth type of list consists of words without semantic relationships private individual ( old, late, thin, wet, hot ).

The results show variations of performances between the lists different according to the type of task (long-term or short-term memory). For the task of short-term memory (immediate ordered recall of list of 5 words) the first type of lists present of large difficulties (10% of correct recall) whereas no difference appears between the three other lists. For the task of long-term memory (recall differed from a list of 10 words) performances with the first two types of lists different step significantly whereas a variation Net is noted between the third (close words sémantiquements) and fourth (words without semantic relationship) lists. These results suggest the use of two codings distinct for the tasks from short-term and long-term memory and thus potentially the existence from two different systems.

Mnemic Empan

A third type of experimental result is also advanced in favor of the short-term memory: the existence of a limited mnemic empan. The mnemic empan indicates the number of elements (in general figures) which one can immediately restore after having heard them.

A traditional experiment consists in reading a list of figures, at a speed given (for example one a second) then to require about restoring them in the order. When the list contains less than 5 elements, the recall does not pose normally a problem. With the top of 7 elements it becomes much more difficult.

The famous article of Miller (1956), The magical number 7+/-2 reviews a series of results which leave think that the short-term capacity storage would be limited to 7 elements.

Neuropsychology

Another series of proof in favor of the existence of a memory in the short run distinct from the long-term memory comes from the Neuropsychologie and the study of amnesic patients.

One of these patients is case H.M. studied by Milner (1966). H.M. underwent a bilateral exérèse hippocampus in order to reduce to them violent crises of the epilepsy from which he suffered. After this operation, H.M severely became amnesic. He still remembered event of his last life but could not retain new information any more. A psychologist could for example come the morning to make him undergo a battery of test, he does not recognize it any more the afternoon and would not have any memory of the morning. On the other hand, H.M. presented performances completely normal to the tasks of empan mnemic what suggests an in the short run intact memory.

An opposite case is described by Shallice and Warrington (1970). K.F had undergone a cerebral lesion and could not memorize any more but two or three digits at the same time. In spite of its memory in the short run severely damaged, K.F has an in the long run important capacity of training.

If each one of these cases taken separately does not prove necessarily the existence of two distinct memories, the double-dissociation between performance with the tasks of short-term and long-term memory convinced the neuropsychologists of the existence of the short-term memory.

Characteristics of the MCT

The storage period of the short-term memory is of a few seconds but one can lengthen this storage period if one calls upon a autorépétition

MCT and working memory

Alan Baddeley proposes a functional model of the memory called in the short run Working memory. This one is organized in a center executive, charged with managing the nelles resources Attention, and two subsystems of capacity and different structures.

The first subsystem is called buckles phonological (or more rarely buckles articulatory) and borrows from an operation of the lexical memory with a autorépétition with low voice (subvocalisation) with all the inherent strategies of retention of lexical information.

The second subsystem is called visuo-space note-book, functioning in relation with the picturesque memory.

It is the executive center, also called main frame, which allocate and distribute information, attention for the active tasks in memory.

One speaks about cognitive competition when two tasks use the same attentionnelles resources and consequently compete with oneself in working memory in way remarkable on the performances.

Other problems involved in the concept of MCT

More

Articles wikipedia

• Memory

• modal Model of the memory
• long-term Memory
• Working memory

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