The Memory of the Feeble-Minded
- Author:
EO. Lewis MA., DSc., MRCS.
Some modern writers on mental deficiency regard the feeble-minded as a class that has some one mental defect in common, varying in degree only. This simple conception is perhaps due to the tendency of late years to emphasise the quantitative aspect of mental deficiency and to neglect qualitative distinctions. But teachers, psychologists, and medical officers, who deal with the practical problems which the mentally defective present, are more impressed by the diversity than by the uniformity of mental types. When dealing with defectives individually it is, to say the least, as helpful to think in terms of Cental types as in terms of mental quotients. Whilst it is generally conceded that the quantitative investigations of the intelligence of children have done much to ensure better and more uniform standards in the certification of the mentally defective, at the same time it is well to avoid the extreme of being tyrannised by decimal points, when dealing with the mentality of children.
Defective memory is more characteristic of certain types of the mentally defective than others. Thus epileptics, especially in cases in which the disease is progressive, present the features of retrogressive amnesia. After a fit, or series of fits, recent events are forgotten, and knowledge last acquired is lost first. Very often, there is loss of memory of all events within certain time limits. Then again, congenital paralytics are said to have poor memories. They do not forget recent events with the same completeness as epileptics. The paralysed child often surprises us by recalling trivial incidents of the past; although he may be unable to repeat a simple task upon which he spent much time and effort quite recently and had apparently for a time thoroughly mastered. But notwithstanding their memory weakness, paralytics frequently acquire considerable proficiency with some special tasks. A congenital paralytic I saw recently whose general appearance is that of an imbecile, can read standard literary works intelligently. Another case whose guardians stated that be was unable to recall even most recent experiences, played draughts and cbess fairly well. Instances of this kind are by no means uncommon; and they show the necessity of further observation in order that we may be able to state more precisely the memory defects of paralytic cases.
A detailed study of the memory defects of these and other clinical types of defectives would be most valuable. This paper, however, deals with some preliminary observations I made of the learning and memory processes of a group of feeble-minded children. The group consisted of various mental types, and data obtained from such a heterogeneous group should obviously be interpreted cautiously .
It may be of interest to state what induced me to collect these data. Mr. Burt in his extensive statistical and experimental studies* has demonstrated how much more retarded defectives are in educational subjects such as reading, writing, and arithmetic, than they appear to be when examined with mental tests. This fact was also brought home to me when I compared the performances of feebleminded boys with formal laboratory tests (such as learning a handmaze blindfolded) and simple educational tests, with the performances of normal children. The disparity was much greater with the educational tests. Several recent researches indicate that the educational retardation of defectives is approximately twice their mental retardation. Why is this? Many reasons suggested themselves. One of these which seems well worth investigation is whether the mentally defective have exceptionally poor memories. The learning of a school subject such as reading is a cumulative process progressing in complexity; and success depends largely upon the pupil’s ability to retain what he has learnt in the initial stages and to recall it as occasion requires.
Teachers of the feeble-minded frequently deplore the inability of the pupils to remember what has been learnt, and several writers straightway infer that the feeble-minded child is greatly handicapped from birth by defect of that physiological endowment called retentiveness. But it is well to bear in mind that memory is a complex process; and comprises at least the three processes of learning, retaining and recalling; and defective memory is by no means synonymous with defective retentiveness. The behaviour of defectives, in some respects, leads us to infer the very opposite, namely, that this mechanical factor of retentiveness, or brute memory, as it has been called, is unduly potent. Enslavement to a restricted group of habits is a characteristic of the mental life of most defectives. Some of the hall-marks of mental deficiency, namely perseveration in speech and automatism in action, are examples of the predominance of retentiveness. The inferiority of the feeble-minded is not due to failure to form certain habits, physical and mental, but rather to inability to form a wide range of these habits. Another a priori consideration that seems to suggest that retentiveness may be a factor of secondary importance only in mental deficiency is that it does not correlate highly with general intelligence. Therefore, it seems that the part played by defective retentiveness in mental deficiency is still an open question; and in this paper the discussion will be limited to this special problem.
It will be helpful, before we proceed to discuss the data of the present investigation, to summarise briefly the conclusions of previous writers. The Chief Medical Officer of the Board of Education in his 1920 Report writes as follows: ‘ ‘Absence or impairment of memory power is the one quality which all mentally defectives hold in common, and with which all other psychological manifestations are related. A child who cannot remember has nothing to store?he has not the mental material to enable him contrast or compare, and thence to form a proper judgment whether in visual or abstract imagery. Consequently, his emotions fail in their proper setting, and his direction towards life, his volition, his action, language, and movements, suffer. He becomes in fact, incapable of managing his own affairs and for the basic reason that his memory power is imperfect.” These remarks naturally carry weight because they express the views of experts who have spent many years in the study of the educational activities of defectives, and because they are probably based upon opinions obtained from teachers of special classes in all parts of the country.
Contrary to expectations, the number of experimental investigations of the memory of mentally defectives are relatively few and meagre. Galton* found that most imbeciles failed to repeat more than four digits: while several imbeciles who had remarkable memories for dates or passages in books showed equally remarkable failure (a span of only three) in immediate memory for digits. Johnsonf concludes from his data that the degree to which the memory of feebleminded children is inferior to that of normal children is net commensurate with the disparity in general intelligence. NorsworthyJ compared normal and feebleminded children as to their memory for related and unrelated words. Her results show that 5% of the feeble-minded do as well with the related-word and 6% do as well with the unrelated-word test, as 50% of the normal children do. Smedley? found that incorrigibles, defectives, and truants, are inferior to normal Pupils in memory power, and the disparity increases with age. Smith’s tests with epileptics show that in the auditory letter-span test they are subnormal and that they make on an average three times as many errors of insertion. Burt in his volume on “Mental and Scholastic Tests” cites several interesting cases of specific memory defects, some of mechanical and rote memory, others of long? and short?distance memories.
“Supplementary Notes on ‘Prehension’ in Idiots. “Mind, 12. 79.
t”Contribution to the Psychology and Pedagogy of Feeble-Minded Children.” Pedog. Semin, 3.245. J “The Psychology of Mentally Deficient Children.” 5 “Report of Dept. of Child Study and Pedag. Investigations.” (Chicago Public Schools) No. 8. H* ‘British Journal of Psychology.” 1.240.
EXPERIMENTAL DATA AND CONCLUSIONS.
How is this basic factor of memory, retentiveness, to be tested ? It was at one time thought that by choosing material devoid of meaning or any other rational associations, for example, nonsense syllables,?nog, vit, zeg, it was possible to measure retentiveness, pure and simple. Psychologists no longer adopt this view. In fact, the learning, retaining, and recalling of a list of nonsense syllables involve a complexity of mental processes not less, to say the least, than those where ‘sense’ material is used. Moreover, the marked failure of many of my defective subjects to learn a short list of twelve nonsense syllables showed the unsuitability of such material. Even after thirty or more repetitions distributed over several days many of them were unable to reproduce the twelve syllables correctly.
It was therefore decided to use tests that would at least interest the mentally defective boys and girls. The material of the tests in the first place had to be such that they could understand easily, and consequently were able to learn thoroughly. Much of the disappointment of teachers when they come to test their pupils is due to the fact that the subject matter had not really been mastered during the learning stage. In much of the immediate or short-distance memory work of children, and especially the mentally defective, there is a delusive proficiency. The fact that a pupil has reproduced a list of words correctly once is not sufficient proof that he has learnt the list thoroughly. In these tests complete learning was not assumed until the child reproduced the task correctly at least three times in succession without any help.
The data of this investigation were obtained by testing sixty feeble-minded boys and girls some of whom were at the Littleton House Residential School, Cambridge, and others at day special schools in Cambridge and London. Their ages varied between eight and sixteen; and their intelligence quotients (as assessed by Binet’s 1911 Scale) varied between .55 and .75, with the exception of four cases whose I.Q’s were higher. Twenty normal children who served as a control group had ages varying between eight and twelve. Their mental ages on the whole were higher than those of the defectives. It would have been better had it been arranged that the mental ages of the two groups were approximately the same.
1. The Construction Test.
In this test the subjects learnt to construct a simple model of an aeroplane. The material used were thirty sticks of various lengths ; in fact there were only four sizes. The sticks could be interlocked by means of notches cut in the sides. Some of the sticks had one pair of notches, others two, three, and four pairs of notches respectively. The subjects copied a model placed before them; and as each subject was tested individually (and this was the case in all the tests here described) every help was given in the learning stage. The subject repeated the construction until it was obvious that he could construct the model without the slighest aid either by looking at the standard model or from the experimenter. Alter a month had elapsed, during which time the subject had no access to the material or to any model, he was asked to construct the aeroplane without receiving any warning that he would be retested. Thirty-five mentally defective children and twenty normal children performed this test. The method of recording the results which I adopted, was to count the number of errors in the completed model. This was no easy task ; and in some cases, it must be admitted, the assessment was somewhat arbitrary. A model with more than twenty errors was regarded a failure. The data may be summarised as follows:?
Number of Errors O. 1?5 6?10 11?20 Failures. Defectives .. 15 3 9 4 4 (Total 35). Normals. …. 11 2 4 2 1 (Total 20).
2. Association Test
The task set in this test was to learn twelve arbitrary associations of letters and pictures; thus the letter B printed on one card was presented simultaneously with the picture of a monkey on another card; and the subject said Monkey?B. The test was given because it embodies a mental process of association of fundamental importance in the initial stages of learning to read ; and it is now realised more clearly than ever, that reading presents very real difficulties to the majority of the mentally defective. The subjects were shown the twelve pairs of associations in series; and they were tested after each presentation. The method used for testing was to spread the pictures of the twelve animals on the table and show one of the letters; the subject wa? required to point to the picture that had been associated with the latter. They were told after each response whether it was right or wrong. The series was shown until the subject gave all twelve responses correctly without hesitation. A week later they were re-tested; and this was repeated three weeks afterwards, that is, a month after the initial learning. Twenty-five defectives took part in this test; and fifteen formed the control group of normal children. The following results were obtained:
..list-table:: Table 2. Number of Errors * -
After
0
1
2
3
5.-f
Defectives l week. 11 2 5 1 3 3 ? (Total 25). 1 month ? 5 3 0 2 4 4 7 Normals. 1 week. 9 2 3 ? ? 1 ? (Total 15). 1 month. 6 1 5 1 ? 2 ? ?
3. Recitation Test
This was a simple educational test of learning a six-line stanza containing thirty-three words. The context of the stanza was such that the lowest of the defectives tested could understand it easily. As with the previous test, reproductions were required a week, and a month later. The method of recording the results adopted, was to count the number of times each subject had to be prompted. Twenty defectives and twenty normal children gave the following results:?
After 0. 1. 2. 3. 5. 5 5?10 Failed. Defectives. 1 week. 13 4 ? 11 ? 1 0 (Total 20). 1 month. 6 12?31 2 5 Normals. 1 week. 10 2 1 ? ? 1 ?? ? (Total 20). 1 month. 11 2 ? 2 2 ? 3 ?
Several other tests such as learning a number of novel geometrical figures, and lists of names of common objects, reproducing simple stories, and describing cinema pictures?these and other simple tests were given, but the data cannot be included in this article, although some of my conclusions are chiefly based upon these data.
The chief feature of the data given in the above tables is the surprisingly good results of the defectives, and especially in the shorter distance memory tests. That in all three tests approximately half the defectives were able to reproduce correctly (in the construction test after a month’s interval, and in the other two tests after a week) was a result I had not expected; and unexpected results have to be interpreted cautiously. Therefore in order to interpret these data rightly, it is necessary to emphasise some of the features of the tests used, and of the methods adopted in this investigation.
In the first place it is well to bear in mind that all three were short-span tests. The defective once he had learnt the construction of the model areoplane could reproduce it in a few minutes; and the association and stanza tests could be reproduced in a few seconds. To argue from these tests to the protracted cumulative processes involved in the learning of ordinary school subjects would obviously not be justifiable. This was soon proved by the comparative results obtained from defectives and normal pupils when set to learn lists of words with ten, fifteen, twenty and twenty-five items respectively. The disparity between the records of the defectives and normal pupils increased at a much greater rate than the ratio of the number of items. Whatever redeeming feature of retentiveness the feeble-minded may possess, it is certainly of very limited span.
The conditions and general methods of conducting these tests also were very different from those that are possible when a teacher has a class of fifteen to twenty pupils. Each child was taught individually; and therefore it was possible to give a measure of help that would be out of the question in class teaching. Special effort was made to ensure that each defective was interested in the tests. Each of the tasks set was well within the comprehension of the defective and meant something to him. It is scarcely necessary to say that results obtained under such ideal conditions are not fair standards for judging the attainments of the mentally defectives taught under modern class conditions.
Again, the emphasis placed upon thorough learning in these tests had much to do with the results. It is only recently psychologists have investigated the subject of over-learning in memory work. In these tests the defectives seemed to profit more than the normal pupils at the over-learning stage. The normal child soon loses interest in simple tasks such as those given on this occasion, when he has repeated them correctly once; but most of the defectives seem to take an added interest in what they had mastered. The joy of ach ievement perhaps is one factor that accounts for the large part played by ‘perseveration’ in the mental life of defectives. My general observation of defectives suggests that over-learning is a subject that may prove of special interest to teachers of the mentally defective. A piece of knowledge or a group of actions, in order to become part of the permanent stock-in-trade of the mentally defective child, has to be assimilated with a thoroughness that we generally associate with the formation of a habit as contrasted with mere memorisation. This emphasis of the need for repetition in the learning processes of the mentally defective is not an endorsement of tedious mechanical grind. As already suggested the defective child finds much pleasure in these repetitions, although no doubt, there is a limit beyond which they become tedious (and therefore unprofitable) even to him.
These particular features of the tests must be borne his mind when attempting to interpret and to apply the results obtained. Nevertheless, it is a fact of no little interest that the group of defectives made comparatively good records in the short-distance memory tests. It is true that in addition to retentiveness there were several other factors that helped to determine the records. But the answer these few data gives to the simple practical question “Do the mentally defective remember what they learn?” is that with simple short-span tests, they compare favourably with normal children during the earlier stages of the forgetting process. The fact has beca appreciated long ago by those who are experienced with the mentally defective. The superintendents of colonies for the mentally defective soon realised that the defective often shows special ability in performing a few well-defined occupations, but that he shows very little versatility. It is doubtful however whether educationists and teachers have made the most of the comparatively efficient short-span and short-distance memories of the mentally defective. Would it not be better to fractionise the curricula of the special school into a number of short well-defined tasks and occupations than to attempt to repeat even on a small scale the curriculum of the ordinary elementary school ?
What about the remote or long-distance memories of the mentally defective ? My data are far too meagre to enable me to make any dogmatic conclusions as to the rate of forgetting; but tney suggest one or two interesting points. Ebbinghaus who used nonsense syllables mostly in his tests with adults, formulated a law that the rate of forgetting is proportional to the logarithm of the time that has elapsed. Thus, according to this law much more is forgotten proportionately during the initial than the later stages. Subsequent investigations have proved that Ebbinghaus’s law, even when regarded as a very rough approximation, exaggerates considerably the rate of forgetting in the initial stages; and the data given in the above tables also suggest this to be the case. The point of special interest, however, is that the records of the mentally defective subjects depart from the law stated by Ebbinghaus to a much greater extent than even those of the normal subjects. The tables indicate that whereas the defectives compare favourably with normals in short-distance memories they are distinctly inferior in long-distance memories. My attention was first drawn to this feature by a decided contrast between two successive records of one of my subjects in recalling a story I had told him. His records at the end of the first, second, and fourth weeks had been fairly creditable. When tested at the end of the second month I could not make my subjert understand what story he was required to recall. I then asked him a number of questions which should have suggested various items of the story; but his failure convinced me that he had completely forgotten it.
This marked poverty of the remote memories of the mentally defective has also been brought home to me when I have met some of my defective acquaintances after a year or more has elapsed. Seveial of them had spent much time with me in performing various tests and in the more pleasant pastimes of games (I hasten to add this last phrase to forestall any uncomplimentary interpretations some of my Freudian friends may suggest). The intervening time produced much greater changes in their external appearance than in mine; but whereas I recognised them immediately, it has been with the greatest difficulty they have been able to recall me: and in more than one case, the defective has obviously forgotten me completely.
It is regrettable that circumstances prevented me re-testing all the subjects who performed the construction test (which is the most interesting of the three tests cited in this paper), so as to give the data necessary to complete table I. I was able, however, to retest twenty-four of my defective subjects and eighteen of the control group of normal children after a period of about three months had elapsed from the time the test had been learnt. Only five of defectives reproduced the model correctly, three others made 1-10 errors, four made 10-20 errors, and the remaining twelve failed badly. In the control group, eight reproduced it correctly, seen made 1-10 errors, two made 10-20 errors and only one failed completely. Therefore in this test also the defectives compare very badly with the normal children in remote memory work.
One characteristic feature of the reproductions of most of the defectives in these tests should be mentioned in this context. When the defective reproduced correctly, it was done without much hesitation or faltering: and in a case where only a portion was remembered this was recalled fairly readily, and no matter how much time and encouragement he was given he did not improve much upon his initial effort. The reproductions of the normal children were frequently very different from this. Often they would make a most unpromising start, but given sufficient time their final results would be creditably if not absoloutely correct. The difference was not merely one of perseverance. The reproductions of the defective showed more of the mechanical precision of habit, whereas in those of the normal subject, rational associations played a most important part. The responses of defectives in these tests reminded me of behaviour that conformed to the all-or-none principle.
This characteristic difference between normal and defective pupils suggests one explanation why the latter group were so inferior in long-distance memory work. The ability of the normal person to reconstruct or recall the events of the distant past is largely due to the fact that the contents of his mind are systematically organised by means of the many-sided associations. It has been proved experimentally the more remote the memory recalled the greater is the relative importance of the associations compared with the mere physiological persistency of impressions,?that is retentiveness. The mentally defective show marked inferiority in ability to form rich and potent mental associations in all learning processes. The conclusion these facts indicate is thai the memory work of defectives is so inferior to that of normal persons primarily because of its poverty ?f rational associations; whereas subnormal native retent’v.vess is a factor of secondary importance only. It is by following this line of thought we are most likely to discover the real cause of the failure of the mentally defective with ta; ks of progressive difficulty such as learning to read.
Some of the individual records in this investigation were of special interest. One boy whose mental defect was largely temperamental, had a verbal memory quite superior to the majority of the normal children. He memorised the thirtythree word stanza after only three repetitions: and reproduced the twelve associations of pictures and letters correctly after two repetitions only. His long-distance memory with these two tests was also distinctly good. With the construction test his records were below the average. In six other cases there was marked disparity between their learning and retaining records; that is, they were exceptions to the general rule that quickest learners remember longest. It was something more than a coincidence that three of these cases were cerebral diplegies, two were hemiplegies, and one was a typical case of congenital syphilis. All six cases had creditable learning records with these tests, but when they were tested a week later they failed badly. Therefore, these cases are exceptions to the majority of the defectives tested, as their defective memory seems to be primarily due to subnormal retentiveness. Cases like these frequently give rise to much difference of opinion. The psychologist or medical officer, if he bases his judgment chiefly upon the responses this type of defective gives to mental tests, is likely to adopt too optimistic a view of the progress that the defectiv e is likely to make. The teacher, on the other hand, soon finds that these defectives make very little progress with school subjects. Congenital paralytic and syphilitic cases are two classes of defectives in which intelligence quotients are apt to be misleading . ?z
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