Since all the pupils in Grammar School B, who were not absent during the periods of examination, were examined, the distribution of these 675 pupils may be serviceable for obtaining a rough idea of the borderlines in terms of points at the different ages from 6-13 inclusive. These individuals “constituted the population of a city grammar school in a medium to poor region and including grades from the kindergarten to the eighth, inclusive.” On account of the small number of individuals at each age the errors are large and the limits should be used only with much caution as an indication of the general trend of the table.
All the scales, it should be noted, have been tried out on immature groups composed only of school children. These would not include those children who are so deficient as not to be sent to school. The borderlines determined with school children, therefore, tend to shut out a slightly larger percentage of all children than of school children. They would, therefore, tend to class slightly too many as deficient. Moreover, the groups tested were probably in communities which are somewhat above the average in ability so that we should be doubly cautious in using the borderlines for the immature.
(c) The change in interpreting the borderline for the immature.
The confusion over the amount of allowable retardation in evaluating the results of Binet tests is illustrated by the variations in practise. In 1908 Binet and Simon said: “On the contrary, a retardation of two years is rare enough; ... Let us admit that every time it occurs, the question may be raised as to whether the child is subnormal, and in what category he should be placed” (79, p. 269). In 1911 they had become much more conservative. With their new scale they stated: “We would add that a child should not be considered defective in intelligence no matter how little he knows unless his retardation of intelligence amounts to more than two years” ([78]). This cautious statement seems to have been converted by the various translators into a rule that every child retarded three years was to be regarded deficient. Drummond, for example, in his translation says: “Should a child's mental age show a retardation of three years as compared with his chronological age, and should there be no evident explanation of this, such as ill health, neglect of school attendance, etc., he is reckoned as deficient mentally” (77, p. 163). Wallin, however, in 1911 kept to the original conservative statement, “children retarded less than three years should probably not be rated as feeble-minded” (211, p. 16).
In his book on Mentally Defective Children, before the 1908 scale had appeared, Binet had adopted the Belgian practise of making a distinction between younger and older children as to the amounts of allowable school retardation before the question of mental deficiency should be raised. As a method of preliminary selection for examination he used a retardation in school position of two years when the child was under 9 years of age and three years when he had passed his ninth birthday (77, p. 42). This practise was carried over into the field of mental tests, and Huey then qualified these limits by the safer allowance of four and three years of tested retardation with the change still at nine years ([129]).
The German standard, formulated by Bobertag and accepted by Chotzen (89, p. 494), is to place the lower limit for the normal as less than three years retardation at ten years of age or less than two years retardation under that age. The change in the amount of retardation allowed came at the same position we advocated instead of at 9 as was earlier suggested.
The early practise in the United States was merely to regard three years retardation as the sign of feeble-mindedness. This custom was even followed in 1914 for all under 16 years of age by Mrs. Streeter in the investigation by the New Hampshire Children's Commission of Institutions in that state. She did not call any feeble-minded who tested over XII (40, p. 79). In both the 1908 and 1911 editions of the Binet scale issued by Goddard, he stated that if a child “is more than three years backward he is mentally defective,” giving no caution about a borderline for the mature. This is a practise which has been followed so far as the immature are concerned, by Goddard's students generally. Kuhlmann carefully avoids the statement of a borderline with both his 1908 and 1911 adaptations of the Binet scale, but he has since advocated using an intelligence quotient of less than .75 with his 1911 scale to indicate feeble-mindedness and leaving a doubtful area from .75 to .80 ([140]). Stern suggested a borderline of .80 with the intelligence quotient ([188]). Even a quotient of .75 would call a child feeble-minded by Kuhlmann's 1911 scale if he tested two years retarded at eight and three years retarded at twelve. Haines suggests using, with caution, a borderline with a modified Point Scale which should be at 75% of the average performance measured in points at each age for individuals over thirteen years, and four years retardation for 13 years and younger ([26]).
Pintner and Paterson collected in one table the test results with the Binet scale published by thirteen different investigators and covering 4,429 children tested (44, p. 49). They do not attempt to readjust these results so as to allow for the very great differences in the methods by which the different groups were chosen to be tested or the different uses of actual life-age and nearest life-age. Such a table is, as they recognize, too hazardous to use for determining the borderlines of deficiency. There might be an average difference of at least a year in the mental ages obtained by different investigators when no allowance is made for their different procedures. Nevertheless, it is interesting to note that a mental quotient of .75 is less conservative than the lowest 3% which is the borderline of feeble-mindedness that they suggest. The lowest 3% they find would include, for example, those who were 1.5 years or more retarded at age 5, 2.1 years retarded at 9 and 2.8 years at age 10.
The most important confirmation of the claim that a borderline for the immature should require at least 4 years retardation comes from the Galton biometric laboratory in London. Karl Pearson has furnished a careful statistical treatment of Jaederholm's results in testing all the 301 children in special classes in Stockholm compared with 261 normal children in the same schools. Pearson found that the modified 1911 Binet scale which Jaederholm used could be corrected so that the normal children at each age averaged very closely to their age norms from 7 to 14 years of age. Under these conditions of the scale he generalized on the basis of the children in the Stockholm special classes who were from 7 to 15 years of age, as follows:
“The reader may rest assured that until the mental age of a child is something like four years in arrear of its physical age it is not possible to dogmatically assert, on the basis of the most scientific test yet proposed as a measure of intelligence, that it is feeble-minded. Even then all we can say is that such a child would be unlikely to occur once in 261 normal children, or occurs under ½% in the normal child population.” (167, p. 18).