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
attempt keep the time interval constant; and by thus ruling out the Goddard scores, the error arising from their re-evaluation
no
to
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 to the institution over a period of thirty-
representing admissions
odd 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. cases were grouped in respect to chronological age at admission, one group coitfaining those from six to sixteen, and the other,
These
those sixteen years and
over.
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 intervenIn each
ing)
was
case
recorded under the
appropriate heading
"Decrease" "No
THE PSYCHOLOGICAL CLINIC
104
change" "Increase." "Decrease" was taken to mean a loss of 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")
five
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 with time.
more
likely
to show
a
decrease than
an
increase
Within the component groups, however, there are several facts be noted. Considering those under sixteen as contrasted with to 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
ment in the distribution of decrease and increase in
disagree-
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 There are several as compared with 16 per cent of the older group. but the most for this explanations logical seems difference, possible 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
Decrease No
change
Increase
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
attempt keep the time interval constant; and by thus ruling out the Goddard scores, the error arising from their re-evaluation
no
to
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 to the institution over a period of thirty-
representing admissions
odd 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. cases were grouped in respect to chronological age at admission, one group coitfaining those from six to sixteen, and the other,
These
those sixteen years and
over.
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 intervenIn each
ing)
was
case
recorded under the
appropriate heading
"Decrease" "No
THE PSYCHOLOGICAL CLINIC
104
change" "Increase." "Decrease" was taken to mean a loss of 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")
five
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 with time.
more
likely
to show
a
decrease than
an
increase
Within the component groups, however, there are several facts be noted. Considering those under sixteen as contrasted with to 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
ment in the distribution of decrease and increase in
disagree-
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 There are several as compared with 16 per cent of the older group. but the most for this explanations logical seems difference, possible 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
Decrease No
change
Increase
