After reading this article you will learn about the physiological, biochemical and psychological basis of memory.
Physiological Basis of Memory:
The theories which claim that memory has a physiological basis often emphasise the brain and neural structures as the seats of memory. Some of the theories taking such a stand are discussed here.
They are the memory trace theory, the cell assembly theory and the interpretive cortex theory:
1. Memory Trace Theory:
Adherents of the memory trace theory proclaim that everything which we encounter or experience is recorded or stored in the form of memory traces. These traces are structural units of the brain, and these units are called neuro-grams or engrams. These engrams are considered to be impressions established in the form of neural structures in the brain. The functioning and composition of the engram is not fully known and is still under exploration.
Moreover, these engrams are not considered to be permanent structures because through measurement of the extent of retention and forgetting we know that learnt matter often undergoes changes and gets lost. Nevertheless, neurosurgical studies prove that when certain parts of the brain, especially the temporal lobes, are electrically stimulated, individuals could recollect vividly certain experiences which were long forgotten.
On the other hand, there is enough scientific evidence to prove that despite stimulation recollection is often not possible. The reason for such loss, according to the trace theory, is a fading of the engram or decay of the trace. Thus, remembering and forgetting are explained in terms of healthy live traces and decayed traces.
2. Theory of Ceil Assembly:
D.O. Hebb suggested that learning consists of the formation of connections between different cells in the brain which finally get established or retained in the form of complex close-cell circuits called cell assemblies. When this circuit is stimulated, the entire assembly is activated and, as a consequence, the entire learning experience is recalled. This is a very common experience.
For instance, sometimes when you try and recollect a single unit of an event or experience, like a word or sentence from a song, the whole song and other experiences associated with it may come back to you in a sequence (even if you do not want it).
Remembering, therefore, is said to result out of stimulation and adequate stimulation leads to perfect recollection. Forgetting, on the other hand, is said to result out of inadequate stimulation. Thus, formation of cell assemblies is considered to be the basis for memory; adequate and inadequate stimulations as the basis for remembering and forgetting.
3. The Interpretive Cortex Theory:
Wilder Penfield, an eminent neurosurgeon, studied over one thousand epilepsy cases. He and J.H. Jackson found that epilepsy is caused due to brain lesion. Patients, during seizures, narrated that they often experienced sensations like strange smells and intellectual auras or dreamy state as immediate precursors or indicators of an epileptic attack.
These auras are conscious images or experiences of the past, sometimes vague and sometimes vivid. Penfield performed craniotomy on the patients, where a portion of the skull was removed and the side of the brain was laid bare. He stimulated the temporal lobe and recreated the memory of a childhood experience that formed the intellectual aura accompanying the epileptic attack each time.
Penfield does not suggest that the interpretive cortex is the seat of memory because surgical removal of the temporal lobe from which a recollection has just been evoked by stimulation does not abolish an individual’s memory of the event just recalled.
But nevertheless, his findings boldly emphasise the permanent recording of experiences in the brain in spite of the process called forgetting which inhibits or forbids remembering. His technique of electrical stimulation, to some extent, suggests that inadequate stimulation may be manifested in the form of forgetting.
Psychological Basis of Memory:
The Memory or storage of learning which has a neural and chemical basis or rather a biological basis. In the following discussion we will see how psychological processes too can provide a basis for memory. The processes described here are primary and secondary memory, motivated memory, trace change and so on.
Primary and Secondary Memory:
This dichotomy of primary and secondary memory is based on psychological processing. The concept of primary and secondary memory was formulated by William James. According to him these two dichotomized storage systems depend on the nature of consciousness.
Information in primary memory was considered to be that matter which is currently in consciousness and that which belongs to the psychological present. Secondary memory items are said to be absent from consciousness at a given point of time and belong to the psychological past. This description, however, was found to be inadequate because it says little about the processing of information in these two systems, the relationship between the systems, etc.
This theory remained dormant for a long time and was revived recently. Today though not in the same shape, it is expressed in the dichotomy model proposed by Endel Tulving. His model dichotomized memory into episodic and semantic memory.
Motivated Memory:
Yet another view that discards all the other views comes from psychoanalysis. This theory claims that an individual will remember what he wants to remember and forget what he does not want to remember. The key concept guiding this motivated memory theory, according to Sigmund Freud, is repression, i. e the unconscious blocking of information having painful or anxiety-provoking associations.
Such associations would manifest themselves through forgetting, a slip of the tongue or pen, etc. in which the speaker or the writer makes an error which is said to reflect his underlying feelings rather than his intended meaning. The clearest evidence shown by Freud to support this concept is hysterical amnesia or fugue, a condition in which a person under emotional stress may be completely unable to recall anything about his life.
Such reactions are fairly common when amnesia is psychological in origin. Traumatic experiences such as those occurring under combat conditions, severe emotional stress, etc. can also produce amnesia. The reader would have surely seen or heard about this type of amnesia or fugue because it has become one of the popular themes of paper-back fictions, television shows and motion pictures.
A case recorded by Masserman is presented here. Bernica L., a forty-two- year old housewife, was brought to the clinic by her family who stated that the patient had disappeared from her home four years ago and had recently been identified and returned from R -, a small town over a thousand miles away.
On rejoining her parents, husband and children she had at first appeared highly perturbed, anxious and indecisive. Soon, however, she had begun to insist that she had really never seen them before and that her name was not Bernica but Rose P and that it was all a case of mistaken identity.
She also threatened that if she were not returned to her home in R – immediately she would sue the hospital for conspiracy and detainment. However, under treatment eventually this patient got readjusted to her actual circumstances. Thus, it can be seen how motivation plays a role in remembering and not remembering an experience.
Trace Change:
The German school of gestalt psychology which flourished in the early part of the twentieth century, though preoccupied with the study of perception, did show some interest in the study of memory also. Their interest in the study of memory was directed towards exploring two specific areas, memory trace and change of the trace due to the organisation of memory.
They predicted that there can be no decay or destruction of the memory trace under normal conditions (no injuries or infections of the brain). Since their perceptual research was confined to ‘form’ their experiments on memory were confined to memory for forms or structure.
These psychologists claim that memory trace for a shape would change progressively over a period of time toward a better, more regular and symmetrical figure. For instance, when you see a triangle or a hexagon with gaps, the memory trace would spontaneously tend more and more towards a perfect triangle and hexagon leading to a good gestalt.
Further research conducted in this area showed that even less organised figures, whether it be shape, form, size, sound, or for” that matter any experiences which are established, in the course of time undergo certain changes. These changes, however, are not erratic and gestalt psychologists identified certain principles which make these changes possible and lead them to good gestalts.
The principles identified are leveling, simplifying, sharpening and elaborating. The way these principles operate can be seen from the following illustration. A three- year old child after learning the alphabets perfectly, was asked to write them after 3 months of vacation; what she wrote is shown in Figs 10.2-10.5. These figures illustrate the concept of trace change.
Some of the changes which occur are as follows:
Leveling is a tendency to reduce the irregularities and make the original object or experience less sharp by dropping the details.
Simplifying is a tendency to make the original figure or sound or experience less elaborate and less complex compared to the one which is being recalled.
Sharpening is the process by which certain details in the memory are accentuated and others are dropped. So some objects and events become more sharply defined in recall than they were in the original experience.
Elaboration is the process by which some objects and events get elaborated in recall than they were in the original experience. The material recalled after a certain period of time, though meaningful and accurate, undergoes changes.
For instance, ask your friend to narrate a story that was read an year ago. If you carefully analyse the content of the story and compare it with the original experience, you will realise that a lot of details have been added, some dropped, some changed, some exaggerated and so on.
Interference Theory:
The theory of interference proclaims that we can store and recollect what we have learnt as long as some other material does not interfere with the material we have already acquired. Interference, however, is inevitable as long as we live. New material or experiences have to be encountered. And this tends to impair the information we are trying to recollect.
Interference may come either from the information we acquired about the item we are trying to remember or from materials memorized earlier. These two types of interferences are called Proactive and Retroactive interference or inhibitions because they inhibit remembering.
Proactive Interference:
When previous information or learning experiences of the past interfere with the retrieval of something which has been learnt recently, it is called proactive inhibition. For instance, try and teach a preschool child two nursery rhymes. After making sure that one has been learnt completely, teach the other. When you ask the child to recollect the rhyme which it learnt later it may start off correctly but end up reciting the one it had learnt earlier.
Retroactive Interference:
It is not always the case that past material interferes and hinders the retrieval of previously learnt information. Recently learnt material can also interfere. This phenomenon is referred to as retroactive inhibition. Take, for instance, the same child who learnt the rhymes. If asked to recollect the one which he or she had learnt earlier he or she may recall the rhyme, but thoroughly jumbled with the later one. Here, interference comes from materials learnt subsequently.
Psychologists working in this area have shown that in both cases the greater the similarity between the interfering events and what is learnt, the greater is the degree of interference. Thus, our vocabulary, experiences, events, etc. in life are so similar that it should not be surprising if there are both proactive and retroactive interferences in our memory.
Recent Trends:
For psychologists working within an information processing framework, a computer provides an apt analogy for what happens inside a person’s head. The computer is taken for a giant brain because both computers and people are considered to be information processing systems. Both computers and humans take in information from the environment; computers do this using card readers, tapes, etc. whereas human beings do it using their sense organs.
Inside the computers, the information from the environment is manipulated, recorded and combined with other information already there by the activation of electronic registers, while the same is done in human beings by the activation of neurons.
A computer conveys information to the environment through output devices such as teletypes and line printers. The human beings convey information through their mouth, hands, etc. Therefore, human behaviour and computer behaviour are viewed as resulting from an interaction between information acquired from the environment and mechanisms present within these systems that process and utilise the information.
This approach also claims that input or the information acquired is processed and then stored. Some of the ways of processing identified information are cueing, coding, recording, categorizing, etc.
A group of psychologists, impressed and influenced by the model of information processing system, explained storage of an experience or memory in terms of processing through various stages. According to them, the storage system is something like a refinery where the raw material undergoes various stages of processing. Whether it is finally discarded or stored depends upon the way it has been processed. The significant stages of information processing are the sensory stages, short-term stage of memory (STM) and long-term stage of memory (LTM).