[14] In trying to explain this success, one must, no doubt, take into account the comparatively advanced age of the children, the probable leniency of the examiners, and, above all, the fact that the ill-balanced subject is a moral rather than a mental defective.
APPENDIX
[N.B.—Throughout the Appendix Roman numerals refer to ages—e.g., IV. 2 = second test for children of four years.]
Part of the interest of this work on defective children consists in the fact that in it we find the origin of those ideas and investigations which culminated in the formation of the Binet-Simon Scale of Intelligence, now so widely known throughout Europe and America.
The ideal that Binet set before himself was the formation of a scale which should measure intelligence in something the same way as the foot-rule measures height. The first difficulty was the unit. If we regard intelligence as the power to cope with a situation, we see that this power in a general way increases with the experience of the child, or, we may say, with his age. A child of nine should have more intelligence than one of eight, a child of eight than a child of seven, and so on. We may suppose, then, that there is a normal intelligence for each age just as there is a normal height for each age, although in the first case, as in the second, many children fall below and many rise above the standard. It is clearly by no means so easy to establish a norm for intelligence as for height, nevertheless, the method should be the same; that is, we should begin by finding out what the intelligence of children of different ages actually is, and from these results we should derive averages which might be used as norms.
In the course of his work with defectives, Binet, as we have seen, had gathered a number of questions which he had found useful as tests of intelligence. He now, in conjunction with Dr. Simon, proceeded to extend the number of these tests and to assign each to its appropriate age. The method he adopted was this: He tried each test on a great number of normal children of the same age. If a large majority answered satisfactorily, he set the test down as suitable for that age; if a majority failed, he moved it to a more advanced age, and tested it again on older children. When we consider his scale then, we must remember that the arrangement is no arbitrary one, but has been derived from actual experiment.
In 1908, after having been tried on over two hundred Parisian school children, the tests were published in the form of a scale, giving a measure of intelligence graded from three to thirteen years of age. By this scale it was held a child's mental age, which, of course, was often not the same as his chronological age, could be determined.
In 1911 there was published a revised scale in which, owing to the results of further experiment and criticism, a considerable number of alterations in the grading of the tests was made. This revised form of the scale is given below. For convenience in use the exact words to be said to the child are placed first, the particular directions for each test being given afterwards. General directions regarding the tests and the method of marking will be found at the end of the scale.