dependence that can be placed upon the I.Q. as obtained by the Stanford revision of the Binet tests as a measure of probable limit

Transcription

1 THE constancy of the intelligence quotient of MENTAL DEFECTIVES Catherine E. Chipman, Psychologist, Walter E. Fernald State School, Waverley, Mass. In any institution in which a psychological examination is a part of the routine of admission, it is of great value to know the dependence that can be placed upon the I.Q. as obtained by the Stanford revision of the Binet tests as a measure of probable limit of mental development. To this end, a study was made of the records in the Psychological laboratory for the comparison of the I.Q. as obtained on admission by the Stanford scale and that on the latest. In those cases in which the admission test was the Goddard 1911 scale, the first I.Q. by the Stanford revision was used as the original. This seemed justified in view of the fact that there was no attempt to keep the time interval constant; and by thus ruling out the Goddard scores, the error arising from their re-evaluation according to Terman was eliminated. Since the results of tests by several different examiners were used, due to rather frequent changes in personnel, the ever-present question of the personal equation is opened. It is impossible to say how much effect differences in leniency of testing may have had on the results, but it is to be hoped that the number of examiners may have served to offset individual differences. This study deals with 1,751 cases, 1,086 males and 665 females representing admissions to the institution over a period of thirtyodd years. According to diagnosis of degree of defect, there is a distribution of 40 per cent morons, 37 per cent imbeciles and 23 per cent idiots, making the aggregate a representative sampling of the defective institutional population. The cases are unselected and constitute the entire number recorded in the psychological index. These cases were grouped in respect to chronological age at admission, one group coitfaining those from six to sixteen, and the other, those sixteen years and over. In each case the I.Q. at admission, or on the first Stanford test, was taken as the basis of comparison, and the discrepancy between it and the I.Q. on the latest test (disregarding any intervening) was recorded under the appropriate heading "Decrease" "No

2 104 THE PSYCHOLOGICAL CLINIC change" "Increase." "Decrease" was taken to mean a loss of five points or more from the original I.Q.; "No change" a variation of not more than four points either gained or lost and "Increase" a gain of five points or more over the original I.Q. The wide range covered by the designation "No change" was due to the fact that with different examiners, a change of less than five points could not be considered significant. Study of the figures and percentages resultant on this procedure, shows that the original I.Q. has been an accurate diagnostic agent (within the limits prescribed as constituting "No change") in four-fifths (79 per cent) of the entire number considered. Of the remaining 21 per cent, 12 per cent show a loss of at least five points and 9 per cent a corresponding gain. It seems reasonable to conclude from this that in those cases in which the original I.Q. has been inaccurate, it is more likely to show a decrease than an increase with time. Within the component groups, however, there are several facts to be noted. Considering those under sixteen as contrasted with those sixteen and over, we find that the proportion of I.Q.'s remaining constant is somewhat larger for the older group, which is quite in accord with the theory that maximum intellectual development is usually reached by the age of sixteen. There is marked disagreement in the distribution of decrease and increase in respect to the original I.Q. In the younger group 15 per cent show a loss as opposed to 1 per cent of the older group; and an inverse ratio holds in regard to increase; 8 per cent of the younger group show such gain as compared with 16 per cent of the older group. There are several possible explanations for this difference, but the most logical seems to be that two types of defective are represented; that which in its extreme form constitutes the "potentially feeble minded"; that is, those who show a spurious evidence of rapid development during their early years but gradually become relatively more and more retarded; and that type which shows a long-continued but very slow rate of growth over a greater number of years than is common. These results are summarized in the following table: Table I Under and over Decrease 15% 1% No change 77% 83% Increase <?? 8% 16%

3 CONSTANCY OF INTELLIGENCE QUOTIENT 105 Considering the group under sixteen years of age at admission, some striking sex differences are apparent. There are approximately twice as many boys as girls in this group and the grade of defect represented is not quite equal. The moron group is the largest for the boys and the imbeciles comprise the largest for the girls. The percentages of cases showing decrease, no change, and increase in I.Q. were figured separately for the males and females according to mental diagnosis "moron," "imbecile," or "idiot." TJnder 16 Table II 16 and over Males Females Males Females Morons 41% 30% 33% 50% Imbecile 35% 40% 50% 40% Hiots 24% 30% 17% 10% In both sexes, the idiots showed the greatest proportion of constant I.Q.'s the imbeciles and morons a progressively smaller percentage. In both sexes, also, the proportion showing decrease in I.Q. is about equal. Here, however, the similarity ends. The percentage of constancy is larger for the males than for the females and the proportion showing increase correspondingly smaller. In fact, the ratio is that of two girls for each boy who shows a five point increase in I.Q. between the first and the last Stanford tests. This proportion holds good no matter what the degree of defect. The following table shows these results for the group under sixteen years of age: Table III Male Female Decrease No change Increase Decrease No change Increase Morons 25% 70% 5% 23% 57% 20% Imbeciles...11% 80% 9% 13% 76% 11% Idiots 7% 90% 3% 6% 87% 7% In the group sixteen years and over at the time of admission the percentage of males and females is reversed, and there are nearly twice as many girls as boys. The findings, however, are in accord with those for the younger group. The boys show a slightly greater tendency toward loss of I.Q. and their proportion of constant I.Q.'s is larger than that of the girls. These differences do not seem great enough to be significant, but a consideration of the "Increase" group brings out the fact

4 106 THE PSYCHOLOGICAL CLINIC that female imbeciles show an increase of at least five points three times as often as the males, and female morons show such gain al- most five times as frequently as do the males. The following table shows the results for the group sixteen and more years of age: Male Table IV Female Decrease No change Increase Decrease No change Increase Morons 4% 90% 6% 2% 70% 28% Imbeciles 1% 96% 3% 0% 90% 10% Idiots 3% 97% 0% 0% 100% 0% These findings need a check, however, because, under the policy of parole effective at present, the girls remain in the institution for a longer period of training than do boys of equal brightness. This would mean that in the file from which the data for this study were taken, there would be a larger number of older, brighter girls which might possibly distort the percentages as recorded. For this reason the group on parole from the institution was studied, since these cases would be comparable on the basis of degree of defect as well as non-institutional environment. Of the fifty-eight cases under consideration, twenty-six boys and thirty-two girls, the percentages showing "decrease" "no change" and "increase" corroborate the findings of the entire group. The boys, with larger percentages of "decrease" and "no change" in the I.Q., show only 27 per cent with an increase of five points or more as contrasted with 47 per cent of the female group. Thus far, the fact seems to be established that while the original I.Q. has been an accurate measure in about eighty per cent of the cases in this study, there still remain twenty per cent to be accounted for. The question which immediately arises is that of the distribu- tion of this number among the moron, imbecile and idiot groups. We already know that 12 per cent of all the cases show a decrease in I.Q., and of this number 63 per cent are morons, 26 per cent imbeciles and 11 per cent idiots. Of the 9 per cent to show an increase, 55 per cent are morons, 35 per cent imbeciles and 10 per cent idiots. It is then, in the moron group that the greatest number of inaccurate predictions on the basis of I.Q. are found. This is only in accord with the common knowledge that the nearer the approach the borderline status, the more difficult a precise diagnosis, and it is included in this study simply to emphasize the need of extreme

5 CONSTANCY OF INTELLIGENCE QUOTIENT 107 caution in applying the I.Q. as the final criterion in the case of high grade defectives. The following conclusions can be reached from the study thus far: 1. The I.Q. as obtained by the Stanford revision of the Binet tests has been a reliable basis of prediction of limit of mental development in 79 per cent of the cases admitted to this institution. 2. The variation found, showed a slight tendency toward de- crease in I.Q. rather than increase, in the entire group. 3. The younger group (those less than 16 at admission) showed more variability than those older, and exhibited a marked tendency toward decrease in I.Q. 4. The girls, irrespective of degree of defect, showed a much larger percentage of gains in I.Q., especially in the older group. 5. The idiots, irrespective of C.A., showed the largest percentage of constant I.Q.s, the imbeciles and morons progressively smaller. 6. The majority of inaccurate I.Q.s fall within the moron group, regardless of C.A. The computation from which the foregoing conclusions were drawn was done on the assumption that development of mental capacity is arrested at the age of sixteen; and since there is disagreement as to whether or not fourteen represents more accurately the limit of such increase, the effect of this substitution upon these conditions may well be considered. The ideal method of settling the question would be by the use of a wide-spread and protracted program of annual testing on a large number of subjects ranging in chronological age from twelve to eighteen?to insure an allowance for those showing unusual retardation or acceleration of develop- ment. The difficulty of conducting an investigation of this sort lies in obtaining a representative sampling of the population, and on this ground the figures which have been used are open to criticism, for they represent a group of 161 cases selected from the total num- ber studied, according to specifications given in detail below. This being true, it can readily be seen that the conclusions drawn from them are applicable to defectives only, and study of the results may indicate that the point of arrest for the feebleminded does not coincide wtith that for the so-called ''normal" group. The value of any measure lies in its reliability, which, in the

6 108 THE PSYCHOLOGICAL CLINIC case of the I.Q. is its constancy (within a range of four points lost or gained over the original). Therefore it would seem that the age of arrest which yields the greater number of constant I.Q.s is the more satisfactory. Of necessity, the group on which the work of this portion of study has been done was a selected one, since it could include only those individuals whose record showed an I.Q. by the Stanford revision before the age of fourteen and another after the age of sixteen. The psychological files contained 161 cases which fulfilled these requirements 95 boys and 66 girls. The distribution according to mental diagnosis '' moron," " imbecile," " idiot,'' was not equal; more than half the entire group are morons, while the idiots make up only seven percent. For each individual the I.Q. before the age of fourteen and after the age of sixteen (using sixteen as the chronological constant) were listed and the discrepancy between them recorded as "loss," "no change" or "gain." In this case, "no change" is equivalent to a variation no greater than four points either lost or gained. A third I.Q. was obtained by using the mental age of the test after sixteen and fourteen as the chronological constant. The difference between this re-evaluation and the original I.Q. of the test under fourteen was tabulated in the same way and from these tables the respective percentages of constant I.Q.s compared. Table V C. A. 14 C. A. 16 Male Female Total Male Female Total Loss 9% 2% 6% 22% 17% 20% No change 31% 27% 29% 75% 65% 71% Gain 60% 71% 65% 3% 18% 9% According to the theory of distribution, a curve showing the scattering of cases under the classification "loss," "no change," "gain" should have the greatest frequency at the "no change" point, since constancy is the criterion of the accuracy of the measure. If such distribution is not present, it is conclusive evidence that the measure is unreliable and cannot be used as a basis for prognosis. In a graphic presentation of our results the normal distribution curve obtained by the use of the sixteen year constant would be completely distorted by the substitution of the fourteen year basal. This is, instead of 114 cases (71 per cent) whose I.Q. showed no significant change when sixteen was taken as the age of the

7 CONSTANCY OF INTELLIGENCE QUOTIENT 109 limit of development of mental capacity, 48 cases (29 per cent) prove accurate when fourteen is used. The results showing the comparative distribution of "loss" "no change," "gain" with the two constant chronological ages do not take account of the fact that a certain proportion of the cases which show "no change" with fourteen as a basal showed a loss in I.Q. when sixteen was used. Therefore, considering only that group which were constant with the sixteen year basal, the 114 cases are re-distributed as follows: Table VI Male Female Total No change 21% 16% 19% Gain 79% 84% 81% In other words, of the entire group of 161 cases, only 22 are not materially affected by the change in basal year, for of the fortyeight cases recorded as constant with the fourteen year constant chronological age, 26 are raised to this category from the original "loss" group. The full significance of this is apparent when we consider the effect upon the I.Q.s of high grade defectives. For example, a girl who, upon her admission to the institution, is accorded 61 per cent of the average intelligence by the Stanford revision, is diagnosed "moron-improvable." By the time she is sixteen or more, improved physical conditions coupled with the more adequate training which the institution offers have succeeded in raising her I.Q. to 72 per cent. Technically this places her in the Borderline group, but in view of lack of judgement, suggestibility and general social inadequacy, she will do much better in an institution for defectives for an indefinite period of time. If, for the sixteen year level we substitute fourteen, the case becomes quite different. The low borderline I.Q. automatically rises to 83 per cent?which corresponds to the Dull-normal category. Common sense, public opinion and the definition of the term itself preclude any possibility of keeping an individual classified as normal, even with the qualifying "dull," in a school for the feebleminded. Therefore, M.J., with a mental age of about eleven and the veneer of assurance which so many high grade feebleminded girls possess, is summarily discharged as a case unfit for the institution and left to shift for herself as best she can. On the other hand,

8 110 THE PSYCHOLOGICAL CLINIC with an I.Q. of 72 per cent, after a suitable period of training she is placed on parole with an employer selected and approved by the school; her activities are carefully supervised, and when she was proved competent to manage her own affairs, she is discharged into a community to which she has already adjusted. In addition to the economic and social implications of the use of the fourteen year chronological constant, there is an appreciable influence on the accuracy of prediction of ultimate pedagogical achievement. Until the age of fourteen the I.Q. has been reasonably constant, and the limit of scholastic development capable of prediction on this basis. For the case between fourteen and sixteen, the difference in basal year has a cumulative effect that cannot be ignored. If fourteen is used as a basal, the I.Q. steadily rises after this age, so that if the grouping is done on this basis alone, there is an increasing probability of misplacement in grade during the last two years of school attendance. Consider the case of John, who is fifteen, with a mental age of eleven years and six months. Shall he continue. in the regular grade?taking two years to com- plete the work or shall he be placed in a special class for older boys where the emphasis will be shifted from scholastic to industrial training? The I.Q. becomes the deciding factor. With the use of sixteen as the constant chronological age John has an I.Q. of 76; using fourteen, his I.Q. is 82. If the latter be considered the basis for recommendation, it is almost certain that he will continue in grade, for the dull-normal usually gains more from association with his peers and superiors than from contact with those less able than himself. In this case, the work presented will become more and more beyond John's grasp and from an edu- cational standpoint his last year of school training will be a com- plete loss. The I.Q. based on sixteen would place John in the borderline group whose members do better to work with their equals or even inferiors, in order that they may experience the stimulus of success in equal competition. Therefore, John would attend the special class for a year and leave school at the end of that time knowing, at best, the rudiments of a trade or at least with some experience in actual manual work. All this has been written on the rather remote possibility of John's attending school until the age of fifteen without coming to the attention of the school authorities for examination. Suppose

9 CONSTANCY OF INTELLIGENCE QUOTIENT 111 now, that, when he was a younster of eleven still struggling in the third grade he had been referred to a clinic and diagnosed "Borderline?advise special class.'' In this case the next four years of his school life would have been spent in academic training adapted to his ability and in manual work which would be preparatory to en- abling him to earn his living. If, now that he is fifteen, his I.Q. is figured on the fourteen years basis we find it to be 82 per cent, as stated above, and the situation is just what it was in the first instance? "dull normal boy, put him in the regular grade." This time John will be more of a burden to the teacher and hindrance to the class than before, for instead of being a leader as in the special class, he is now the well-known "lame duck" trailing in the rear, always outdistanced by his fellows and increasingly conscious of his shortcomings. This situation is more than likely to develop in the boy a very objectionable social attitude and lead to difficulties more serious than the school room misconduct by which he hopes to gain a sort of supremacy. Much has been written concerning the seriousness of branding an individual "feebleminded, '' but the emphasis must not be so placed as to obscure the importance of recognizing and dealing with the defect present in the borderline group, for their own protection as well as that of society. In any institution of this sort there are inevitably a few individuals with I.Q.s over 75 per cent who, though they cannot be called "feebleminded" on this basis alone are misfits in the community. Of the 161 cases considered in this part of the study, there were 11 who belonged in this group on admision, eight boys and three girls. According to the latest test, this number was reduced to six, four boys and two girls; showing that nearly half the cases which seemed hardly defective enough to warrant admission have settled to their real mental level. These six comprised 4 per cent of the entire group?about the proportion of atypical cases one would expect to find in any distribution. Ee-evaluation of the latest I.Q. on the basis of fourteen years as the chronological constant changes this number to 47 (17 girls and 30 boys), or about 30 per cent. In the light of the evidence presented, it can be seen that the use of fourteen as the age at which intellectual development ceases destroys the validity of the I.Q. as a diagnostic or prognostic agent, and renders worthless a scale which has proven itself reliable in the great majority of cases in which it has been employed.