Read the articles below and, in a paragraph of not more than 250 words, discuss the problems that students might have with regard to memory and suggest some solutions.
What is your memory?
Memory is the capacity for storing and retrieving information. Without it we would be unable to see, hear or think. We would have no language to express our plight, and indeed no sense of personal identity. In short, without memory we would be vegetables, intellectually dead. This may seem paradoxical since one hears of people losing their memory who, although incapacitated, are nevertheless quite capable of perceiving, thinking and talking. Why is this possible if they have lost their memory? The reason is simple. Human memory is not a single unitary function like the heart or the liver. It consists rather of a whole series of complex interconnected systems which serve different purposes and behave in very different ways. The one function that these systems have in common is that of storing information for future use. In short, you do not have a memory, you have many memories. Consequently someone who is said to have lost their memory is someone who has a malfunction in one or more of these systems. Had all of them been lost, the person would be unconscious and probably dead.
How many kinds of memory?
An obvious next question is how many memories does a human being have? Unfortunately, as with most questions regarding human memory, there is no simple answer. Once we begin to categorize the human memory system we enter the realm of theory, an area in which there are no true answers, merely those which provide a more complete and satisfactory interpretation of the available evidence. That is not of course to say that what follows is simply personal opinion, the bulk of what I shall describe is verifiable evidence about human memory. Such evidence places considerable constraints on any theory, and the theories in turn suggest where one should look for further evidence.
The structure of human memory
Throughout this article, I assume human memory to be broadly divisible into three major systems. The systems interact with each other, and can each be split into sub-systems. These systems are long-term memory, short-term memory and sensory memory. We are not, though, trying to say that there are three separate physiological structures within the head representing the three aspects of memory. We are simply expressing the fact that the three types of memory differ in certain important ways and that it is useful to express this fact by representing the three memory systems separately.
Of the three types of memory described above, that which would correspond most closely to the layman’s view of memory is long-term memory. This represents information that is stored for considerable periods of time. Indeed, as we shall see later, some would claim that information in memory never disappears, but simply becomes less and less accessible. Remembering your own name, how to speak, where you lived as a child, or where you were last year or indeed five minutes ago are all assumed to depend on long-term memory. Such memory is primarily concerned with storing information, unlike sensory memory and short-term memory where the storage is an incidental feature of other aspects of the system.
To an experimental psychologist the phrase ‘long-term memory’ refers to information which is stored sufficiently durably to be accessible over a period of anything more than a few seconds. The reason for this is that, on the whole, memory tested after one or two minutes seems to behave in much the same way as memory tested after one or two days, or years. The same does not apply, as we shall see in due course, to memory tested after one or two seconds, or milliseconds. Is long-term memory a unitary system? This is still a controversial question. Distinctions of at least two types are, however, commonly made.
Episodic and semantic long-term memory
A few years ago the Canadian psychologist, Endel Tulving (1972), pointed out a useful distinction between two types of long-term memory: episodic memory, which involves remembering particular incidents such as having breakfast this morning, and semantic memory, which essentially concerns knowledge about the world. Knowing the meaning of a word or the chemical formula for salt or the capital of France would all be examples of semantic memory. There is no doubt that there are differences between specific personal memories of individual incidents and generalized knowledge of the world, which has often been acquired over a considerable period of time. Whether these represent separate memory systems or different aspects of a single system is still uncertain. The distinction is however a convenient and useful one.
Long-term perceptual memory
A great deal of research on human memory has used verbal materials, since words are easy to present and the subject’s responses easy to record and score. In recent years researchers have increasingly asked whether memory for verbal materials is characteristic of all memory, and in particular whether memory for non-verbalizable sensory experiences relies on quite different memory systems. Undoubtedly we can remember the taste of cheese or the smell of burning rubber or the sound of the sea breaking on a rocky shore without using verbal descriptions of these experiences. Are there separate auditory and visual memory systems, or an all-embracing memory system which is capable of encoding all our experiences? Taking this latter view much verbal learning is verbal only in as much as the material is presented verbally and the subject responds verbally, what is stored is the experience conjured up by the verbal material. Fortunately the general rules which apply to the learning of verbal material also seem to apply at least broadly to remembering pictures or sounds, so the overall conclusions drawn are still likely to hold whether we finish up with the conclusion that long-term memory is a unitary system, or a dual or multiple one.
If you are to understand this sentence, you need to remember the beginning of the sentence until you get to the end. Without some kind of memory for the words and the order in which they occur, language would be incomprehensible.
Suppose I ask you to multiply 23 by 7 in your head. Try looking away from the page and doing this. Presumably in order to come up with the answer you first of all need to remember the number, you then need to multiply 3 by 7, and note that the answer is 21. You then need to remember the 1 and carry the 2, another task which involves remembering. You next multiply the 2 by 7, retrieve the 2 that you carried, making 16, retrieve the original 1 and come up with the answer 161. All of this involves a good deal of temporary storage of numbers, all of which need to be retrieved accurately and at the appropriate time. Having completed the sum there is no further need to retrieve information such as which number was carried, and it seems unlikely that after a couple of similar sums you would be able to remember this information.
In both the language comprehension and the arithmetic case therefore there is a need for the temporary storage of information in order to perform some other task - in these cases, understanding or calculating. Once the task has been achieved, the information stored is no longer required. Short-term memory is the name given to the system or, perhaps more appropriately, set of systems which allow this temporary storage of information which is essential for a brief period of time, and subsequently quite irrelevant.
To what extent does short-term memory represent a system which is quite different from long-term memory? Here again there has been considerable controversy over recent years. One view is that short-term memory represents the same system as long-term memory, but is used under rather special conditions which lead to very little long-term retention. The alternative view, which I myself support, is that long- and short-term memory involve separate systems, although they are very closely integrated in operation. I myself would further argue that short-term memory represents not one but a complex set of interacting sub-systems.
When you go to the cinema, you see what appears to be a continuous scene with people moving in it apparently quite normally. What in fact is presented to your eyes is a series of still pictures interspersed with brief periods of darkness. In order to see it in the way that we do, it is necessary for the visual system to store the information from one frame until the arrival of the next, and subsequently to put them together in a way that makes them appear as a single scene with continuous movement. The visual store responsible for this is one of a whole series of sensory memory systems that are intimately involved in our perception of the world.
Even within visual memory there is probably a whole series of components which are capable of storing visual information for a brief period of time. If you move the end of a brightly glowing cigarette in a darkened room you will find that a trace is left behind, so that you can write a letter with it and have someone recognize it. This effect was used to measure the duration of the visual sensory memory trace as long ago as 1740 by a Swedish investigator, Segner, who attached a glowing ember to a rotating wheel. When the wheel was rotated rapidly, a complete circle could be perceived, since the trace left at the beginning of the circle would still be glowing brightly by the time the coal got hack to its starting point. If the wheel was moved slowly, only a partial circle would be seen, since the trace of the first part would have faded before the ember reached it again. By rotating the wheel at a speed which just allowed a complete circle to be drawn and then measuring the time for one revolution, Segner was able to estimate the duration of this brief sensory store. He found it to be approximately one-tenth of a second.
This phenomenon, known as persistence of vision, can be demonstrated even more simply. Spread out the fingers of your hand and pass them in front of your eyes. Do so slowly at first, and you will notice that the scene seems unstable and tends to jump about. Now move them to and fro rapidly. You will then see what appears to be the normal scene, possibly with a slight blur in front of it. In the rapid movement condition, the scene is interrupted only briefly, hence allowing the information on your eye to be refreshed before it has faded away.
There are at least two and probably more components to sensory visual or iconic memory as it is sometimes called. One of these appears to depend on the retina of the eye and is primarily influenced by the brightness of the stimulus presented. The second one occurs at a point in the brain after the information from the two eyes has been coordinated. It is much more sensitive to pattern than to brightness, and represents the operation of a system involved in shape recognition.
An analogous series of sensory memories occurs in hearing. If I were to present an extremely brief click in one corner of the room, you would be very good at deciding from what direction the click came. In order to do this, you would use the tiny difference in the time of arrival of the click at your two ears, performing a task analogous to the use of sonar to locate the position of a ship. However, in order to make use of this discrepancy in time of arrival of the click at the two ears, it is necessary to have a system which will store the first click until the arrival of the second, allowing this difference to be estimated extremely accurately. While one would not term this a memory system in the usual sense, it certainly is a system for storing and retrieving information and as such can legitimately be described as a very brief sensory memory system.
The existence of a rather more durable auditory memory system can be shown as follows. Suppose I were to read out to you a series of nine-figure telephone numbers. The chances are that you would get most figures of each number right, but would tend to make errors. If I then switched to a system of presenting the numbers visually, one figure at a time, you would find that you made rather more errors, particularly towards the end of the sequence. The graph below shows a typical error pattern for nine-figure sequences both for those that are read and those which are heard. The higher the graph, the greater the number of errors.
The most striking feature of the graph below is the discrepancy between the two modes of presentation in the case of the last item presented. When it is spoken, it is almost always correctly recalled, whereas when it is presented visually, errors are very numerous. The reason for this appears to be that when the sequence is spoken, the last item can still be recovered from a brief auditory memory. The system is sometimes referred to as echoic memory since it is rather like an echo lingering on after the item has been spoken. The echo is limited to one or possibly two items. Consequently it can be wiped out by presenting a further irrelevant item afterwards. Echoic memory is left holding the irrelevant suffix instead of the last number. Hence if I had spoken the sequence of digits to you, and then followed it with the spoken instruction ‘Recall’, the advantage of the last item would have disappeared. The system involved in echoic memory of this type seems to be particularly geared to speech, since a simple but meaningless spoken sound such as ‘bah’ will disrupt performance whereas a pure tone of similar loudness and duration will not. A sequence of spoken numbers is better remembered than a sequence of numbers presented visually because auditory sensory memory appears to be more durable than visual.
Auditory sensory memory is not however limited to speech sounds. Suppose you are dubious about some component in your car engine and you listen to it while driving. What you will be trying to perceive is a repeated sound amidst the relatively random engine noise. In order to perceive the repetition you need to be able to store a long enough period of sound to be able to detect that one feature is recurring. This effect has been used to study auditory memory as follows: the listener is presented with a tape which recycles a sample of randomly fluctuating noise. The size of the sample is then systematically varied. Hence if the sample were half a second long, he would be required to perceive features that were recurring every half second. For the subject to be able to detect this, he would need an auditory memory system that stored at least half a second’s worth of sound. If the sequence was repeated only every second, then a more durable memory store would be needed in order to detect the rhythmic fluctuation. When faced with this task, subjects vary somewhat in their capabilities, but on average can detect repetitions separated by up to three seconds, indicating an auditory memory system of at least this duration.
(From: Your memory: A user’s guide. by Alan Baddeley, London, Penguin, 1986, pages 11-17)
The decline that takes place is a discouragingly steep one - within 24 hours of a one-hour learning period at least 80 per cent of detailed information is lost. This enormous drop in the amount remembered must be prevented, and can be by proper techniques of review.
If review is organised properly, the graph can be changed to keep recall at the high point reached shortly after learning had been completed. In order to accomplish this, a programmed pattern of review must take place, each review being done at the time just before recall is about to drop. For example, the first review should take place about 10 minutes after a one-hour learning period and should itself take 10 minutes. This will keep the recall high for approximately one day, when the next review should take place, this time for a period of 2 to 4 minutes. After this, recall will probably be retained for approximately a week, when another 2 minute review can be completed followed by a further review after about one month. After this time the knowledge will be lodged in Long Term Memory. This means it will be familiar in the way a personal telephone number is familiar, needing only the most occasional nudge to maintain it.
(From Use your head, London, BBC Publications, 1974, p. 55, by Tony Buzan. )
Advice on memory and learning
Exposing the scientific basis of training in memory, and of study skills advice supposedly based on the psychology of learning, is like shooting fish in a barrel.
The forgetting curve
The main characteristic of memory, highlighted in advice (cf. Buzan 1973) is usually that things are forgotten very quickly indeed unless something is done about it. There is frequent reference to the dramatic and awe-inspiring forgetting curve (cf. Freeman, 1972).
Graphs of the curve appear in all sorts of study skill books, usually displaying a bold disregard for labelling or graduating the axes or saying from whence the curve came. In fact it comes from Ebbinghaus (1885). He himself learnt long lists of nonsense syllables (e.g, FUJ, BEH, . .until he could remember them all. Then he waited for various lengths of time and saw how many times he had to go back through the list before he could remember them all again. His measure of retention was, therefore, how much effort had been saved in relearning the list. He found that after about twenty minutes he had to look through the list half as many times as he had done originally. This is interpreted by Buzan (1973) as meaning that fifty per cent of all learning is forgotten after twenty minutes. As any elementary educational psychology textbook will tell you there are some problems with such an interpretation:
Clearly the forgetting curve is of extremely dubious relevance to student learning. This has not prevented Buzan (1973) and Main (1977), for example, from going on to give advice to students on the basis of what happens to this curve when you rehearse.
A graph is prepared, based rather loosely on Jost's law (1897). It is derived from exactly the same experimental paradigm as Ebbinghaus employed. Successively relearning the list of nonsense syllables results in successively shallower forgetting curves. It is concluded, in study skills advice, that to slow the relentless march of forgetting, you need to rehearse your material, at successively longer intervals. This must involve, says Buzan, rehearsing your notes immediately, after one day, one week, one month, etc. Apart from all the objections to the evidence for this phenomenon, outlined above, there are bizarre possibilities in store for any student who should follow such advice. A conventional student attending, say, four lectures a day and also taking notes from, say, two text sources a day, would, after only five weeks, be rehearsing 120 sets of notes a week! I have never met a student who would be willing to undertake such a task.
(From: Teaching students to learn. Graham Gibbs pp. 61-63 Open University Press, 1981)
Peterson and Peterson’s Trigram Retention Experiment (1959)
Peterson and Peterson wanted to study the rate of ‘pure’ short-term forgetting when no rehearsal is allowed.
Their stimuli consisted of three consonants (called a trigram), which had to be recalled after an interval of 3—18 seconds during which time subjects did an interpolated task to prevent them rehearsing. The experiment consisted of many trials, each consisting of the following sequence:
Peterson and Peterson scored the subjects’ recall, marking letters correct only when they were reported in the same place in the sequence as in the original. For example, if a subject recalled ‘XJP’ for ‘XPJ’, he or she was scored as recalling only one correct item. The results are shown in Figure 1 . 1 . The average percentage correct recall of trigrams is high with short delays, but falls as the delay period increases. After 18 seconds of delay, subjects were correctly recalling only just over 10 per cent of the trigrams.
Figure 1.1 The percentage of trigrams correctly recalled, as a function of delay before recall (Peterson and Peterson, 1959)
The fact that material in short-term memory (STM) is forgotten within a period of 6-12 seconds if it is not rehearsed was interpreted by Peterson and Peterson as evidence of the rate of decay of a short-term memory trace.
(Gillian Cohen, Michael, W. Eysenck & Martin LeVoi, Memory: A cognitive approach. Buckingham, Open University Press, 1986, p. 16)
The fact that anything is easier to learn if it is meaningful may simplify life for the student, but it plays havoc with psychological experimentation. Experiments become “contaminated” when subjects can use prior knowledge to help them with the task. As a result, psychologists developed a way to look at learning that is “pure”, in the sense that it is completely independent of meaning. They invented the nonsense syllable, usually a pronounceable three-letter consonant-vowel-consonant sequence such as TAV, ROP or ZIT. And since that invention a large part of psychological theorizing about human learning has been immersed in nonsense - looking at how nonsense syllables are learned, retained and forgotten - even though the intention is to make both the task and the content as different as possible from anything that anyone in his right mind would otherwise endeavour to learn. But there has been a constant war between experimenters struggling to find syllables that are more and more meaningless and experimental subjects trying to confound them by making sense out of the nonsense. There is nothing malicious in this subversive activity on the part of experimental subjects: it seems a natural tendency of human beings to make as much sense as they can out of anything they are asked to do. It is remark-ably easier to remember anything if you can associate it with something sensible - which means something you know already - no matter how bizarre or outrageous the association might appear. (p. 155)
The nonsense syllables TAV, ROP, ZIT, for example, are much easier to remember if they are imagined as a perverse instruction by a drunken ship’s petty officer on shore leave: “Tavern ropes, sit!” Imposing sense or order on a sequence of unrelated items makes them much easier to learn, even if there seems to be much more to learn. (p. 156)
It is difficult to conceive of any actual learning situation outside of the experimental laboratory - with the unfortunate exception of some class-rooms - in which the subject of learning is completely devoid of sense and totally unfamiliar. “Pure” learning is in fact the most impure you could get. Even when a real life learning task looks like list or paired associates learning, it is never as nonsensical or as unpredictable as the laboratory task, and always has an element of meaningfulness. (p. 158)
It is possible to be more specific about the factors that tend to make learning tasks more meaningful. Meaningfulness is increased when
(Comprehension and learning by Frank Smith 1975 New York: Holt, Rinehart & Winston)
Ebbinghaus: Hermann (1850-1909) German psychologist, born at Barmen, near Bonn. He is best remembered for Úber das Gedächtnis (1885, Memory), which first applied experimental methods to memory research, and which introduced the nonsense syllable as a standard stimulus for such work. He taught at Berlin, and became professor at Breslau (1894-1905), then at Halle, where he died.
(From: The Cambridge Encyclopaedia,1997, p. 387, published in London by Cambridge University Press)
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