What are the various methods used for the measurement of human memory?

Memory is an internal and unobservable process. At times we feel that we don't remember all that we had learnt earlier. In such a situation, we come face to face with the imperfect nature of our own memories- our cognitive system for learning, storing, and retrieving information and throwing a challenge for its assessment. The credit for the first systematic assessment of memory goes to Ebbinghaus (1900).

Since then several studies have been reported in which various methods of assessing (measuring) memory have evolved. The amount of information retained in memory can be inferred from observable performance on various tasks. There are both direct and indirect methods of measuring memory.

The direct methods of assessing memory are: (i) recall, (ii) recognition, (iii) relearning, and (iv) reconstruction. The indirect method focuses on the amount of transfer of previous learning to a subsequent learning situation.

Recall

The most widely used method of testing memory or measuring retention is the method of recall. It is a passive, but direct method of measuring retention. Reproduction of learnt materials after a time span is recall. It is actually repetition of learned material, i.e., verbatim (word for word) recitation. For example, one may recall a poem by reciting it even if he does not remember the circumstances under which he had learned.

Recall involves verbal reproduction or repetition of previously learnt material. Recall becomes easier when materials are meaningful, interesting, short, and over learned. Recall is often categorized into: (i) Free Recall and ii) Serial Recall.

I. Free Recall:

Free recall allows us to summon up pieces of information out of order. For example, we may listen to a lecture and afterwards remember a few important quotes without recalling the order in which they were presented. Thus, in free recall, pieces of learnt materials may be recalled freely without following any specific order.

II. Serial Recall:

In serial recall the material is recalled in a very specific order i.e., in which it has been learned. For example, there are people (who) when asked the question- what is twelve multiplied by seven- may start from the beginning of multiplication chart twelve, and only then can recall the correct answer.

Ebbinghaus (1885) used recall method for studying remembering and Drgetting. He was of the view that retention can be tested either by the method of (i) immediate recall or, (ii) delayed recall, When recall is made immediate after learning, it is called 'immediate recall'; whereas, when recall is made after an interval of time, it is called 'delayed recall'.

It may be noted that failure to recall does not necessarily mean that there has been no retention. Fai to recall despite retention is known as recall amnesia. Sometimes du emotional disturbances like fear, anxiety and sudden shock, one fails to recall. Further, when the subject is motivated to learn, she/he can recall the items easily. Thus, motive plays a major role in recall.

Recognition

Recognition is considered as a sensitive method of measuring retention It is an active process where identification of elements takes place. Recognition is a common experience which refers to the fact that once the remembered event or word is in front of us, we know that we have stored it away before is familiar to us. Guilford (1917) viewed that recognition means knowing again Further, the essential difference between recall and recognition is that in first case, the stimulus is not there for one's identification, whereas it is there in the second case.

Thus, recognition is the identification of learnt material object from a combination (combined list) of learned and unlearned material The correct identification will provide the raw retention score. The percent of recognition can be derived by using certain formula.

Percentage of Recognition =

R – W/ K-1 x 100/n

Where R =Total number of items correctly recognized.

W = Total number of items incorrectly recognized.

K= Total number of alternatives given for recognition (old + new).

N= Number of items originally presented for learning.

For example, let the learner recognize 4 out of 10 items with 10 alternates.

Then, percentage of Recognition

4- 6 / 20-1 X 100/10 = 36.8%

Recognition is easier than recall, because in recognition, the object present in a mixed form with certain new elements. The sensitiveness is greater in case of recognition, which is sometimes influenced by the subject's attitude, prejudice, values, and other inner motives. Seeleman (1940) conducted an experiment on the role of motivation in recognition and observed that pleasant experiences are better remembered than unpleasant experiences.

Further, it has been reported from other studies that with the increase of similarity between original learning materials to that of the new materials, recognition incomes difficult. While studying the process of recognition, usually two kinds of errors are noticed. They are:

(i) Failure to recognize the familiar items, and

(ii) False cognition of the new and unfamiliar items.

We fail to recognize the familiar object, when it is seen under changed circumstances. We accept a new stimulus as the old stimulus when there is 2 lot of similarity between the two. The greater amount of similarity facilitates larger errors in recognition.

Studies conducted by Skaggs and Robinson suggest that as similarity between the interpolated activity and original learning is reduced to a near identity, retention falls to a minimum and then rises again, but with decrease in similarity it never reaches the level obtained with maximum similarity."

Relearning

The method of relearning is the most sensitive among all measures of retention. This method is otherwise known as the method of 'saving', which was introduced by Ebbinghaus (1885) for measuring the quantitative aspect of memory. In this method, a list of materials is presented to the subject up to perfect learning, and after a time gap, she/he is presented with the same list to relearn. The experimenter records the number of trials and time taken by the subject in relearning condition. The percentage of saving is found by the formula-

OLT-RLT / OCT X 10

Where OLT = Original learning trials RLT = Relearning trials For example, if a child takes 8 trials to learn the original task and 6 trials to relearn it, then the percentage of saving is = (8-6 / 8) X 100 = 25%

Reconstruction

Reconstruction involves the reproduction of the learned materials. Reconstruction technically means rearranging the parts of an original task, presented randomly. In this method, the stimuli are first presented in a certain arrangement, then this arrangement is broken up and the stimuli are handed over to the subject with instruction to reconstruct the original order.

Suppose the parts of a plastic doll are joined to get a full figure of a doll, then the experimenter breaks it into pieces and asks the subject to rearrange the items to form a doll. If the subject can rearrange, then she/he gets the full credit for the test. Similarly while writing an essay on Second World War, we recall that the United States entered the war in 1941 after the attack on Pear Harbour, and an atom bomb was dropped on Hiroshima in 1945. Hence, we are able to reconstruct the events that took place between these two times.

The limitation of this method is that only such materials, which are breakable into parts, can be used for experimentation.

The methods of testing retention i.e., recall, recognition, relearning and reconstruction are the basic units of assessing memory. But the question how information is stored in memory has encouraged the researchers in the past.

William James distinguished memory into primary memory and secondary memory. But with the advancement of research and electronic devices, the idea of multiple memories came into light. Most researchers believe that computer memory can be used as a rough working model for understand^ human memory.