The Measurement of Intelligence. Lewis M. Terman

guidance of children, telling us which will succeed in business, which in art, which in medicine, etc. It is not a new kind of phrenology. At the same time, as we have already pointed out, it is capable of bounding roughly the vocational territory in which an individual’s intelligence will probably permit success, nothing else preventing.[14]

      In the third place, it must not be supposed that the scale can be used as a complete pedagogical guide. Although intelligence tests furnish data of the greatest significance for pedagogical procedure, they do not suggest the appropriate educational methods in detail. These will have to be worked out in a practical way for the various grades of intelligence, and at great cost of labor and patience.

      Finally, in arriving at an estimate of a subject’s grade of intelligence and his susceptibility to training, it would be a mistake to ignore the data obtainable from other sources. No competent psychologist, however ardent a supporter of the Binet method he might be, would recommend such a policy. Those who accept the method as all-sufficient are as much in error as those who consider it as no more important than any one of a dozen other approaches. Standardized tests have already become and will remain by far the most reliable single method for grading intelligence, but the results they furnish will always need to be interpreted in the light of supplementary information regarding the subject’s personal history, including medical record, accidents, play habits, industrial efficiency, social and moral traits, school success, home environment, etc. Without question, however, the improved Binet tests will contribute more than all other data combined to the end of enabling us to forecast a child’s possibilities of future improvement, and this is the information which will aid most in the proper direction of his education.

      FOOTNOTES:

       Table of Contents

      [10] See Part II of this volume, and References 1 and 29, for discussion and interpretation of the individual tests.

[11] See Binet and Simon: “L’intelligence des imbeciles,” in L’Année Psychologique (1909), pp. 1–147. The last division of this article is devoted to a discussion of the essential nature of the higher thought processes, and is a wonderful example of that keen psychological analysis in which Binet was so gifted.

[12] See especially pages 162 and 238.

[13] See p. 55.

[14] See p. 17.

CHAPTER IV

       NATURE OF THE STANFORD REVISION AND EXTENSION

       Table of Contents

      Although the Binet scale quickly demonstrated its value as an instrument for the classification of mentally-retarded and otherwise exceptional children, it had, nevertheless, several imperfections which greatly limited its usefulness. There was a dearth of tests at the higher mental levels, the procedure was so inadequately defined that needless disagreement came about in the interpretation of data, and so many of the tests were misplaced as to make the results of an examination more or less misleading, particularly in the case of very young subjects and those near the adult level. It was for the purpose of correcting these and certain other faults that the Stanford investigation was planned.[15]

Sources of data.

       Table of Contents

      Our revision is the result of several years of work, and involved the examination of approximately 2300 subjects, including 1700 normal children, 200 defective and superior children, and more than 400 adults.

      Tests of 400 of the 1700 normal children had been made by Childs and Terman in 1910–11, and of 300 children by Trost, Waddle, and Terman in 1911–12. For various reasons, however, the results of these tests did not furnish satisfactory data for a thoroughgoing revision of the scale. Accordingly a new investigation was undertaken, somewhat more extensive than the others, and more carefully planned. Its main features may be described as follows:—

      1. The first step was to assemble as nearly as possible all the results which had been secured for each test of the scale by all the workers of all countries. The result was a large sheet of tabulated data for each individual test, including percentages passing the test at various ages, conditions under which the results were secured, method of procedure, etc. After a comparative study of these data, and in the light of results we had ourselves secured, a provisional arrangement of the tests was prepared for try-out.

      2. In addition to the tests of the original Binet scale, 40 additional tests were included for try-out. This, it was expected, would make possible the elimination of some of the least satisfactory tests, and at the same time permit the addition of enough new ones to give at least six tests, instead of five, for each age group.

      3. A plan was then devised for securing subjects who should be as nearly as possible representative of the several ages. The method was to select a school in a community of average social status, a school attended by all or practically all the children in the district where it was located. In order to get clear pictures of age differences the tests were confined to children who were within two months of a birthday. To avoid accidental selection, all the children within two months of a birthday were tested, in whatever grade enrolled. Tests of foreign-born children, however, were eliminated in the treatment of results. There remained tests of approximately 1000 children, of whom 905 were between 5 and 14 years of age.

      4. The children’s responses were, for the most part, recorded verbatim. This made it possible to re-score the records according to any desired standard, and thus to fit a test more perfectly to the age level assigned it.

      5. Much attention was given to securing uniformity of procedure. A half-year was devoted to training the examiners and another half-year to the supervision of the testing. In the further interests of uniformity all the records were scored by one person (the writer).

Method of arriving at a revision.

       Table of Contents

      The revision of the scale below the 14-year level was based almost entirely on the tests of the above-mentioned 1,000 unselected children. The guiding principle was to secure an arrangement of the tests and a standard of scoring which would cause the median mental age of the unselected children of each age group to coincide with the median chronological age. That is, a correct scale must cause the average child of 5 years to test exactly at 5, the average child at 6 to test exactly at 6, etc. Or, to express the same fact in terms of intelligence quotient,[16] a correct scale must give a median intelligence quotient of unity, or 100 per cent, for unselected children