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. CHAPTER IV NATURE OF THE STANFORD REVISION AND EXTENSION 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] [15] The writer wishes to acknowledge his very great indebtedness to Miss Grace Lyman, Dr. George Ordahl, Dr. Louise Ellison Ordahl, Miss Neva Galbreath, Mr. Wilford Talbert, Dr. J. Harold Williams, Mr. Herbert E. Knollin, and Miss Irene Cuneo for their coöperation in making the tests on which the Stanford revision is chiefly based. Without their loyal assistance the investigation could not have been carried through. Grateful acknowledgment is also made to the many public school teachers and principals for their generous and invaluable coöperation in furnishing subjects for the tests, and in supplying, sometimes at considerable cost of labor, the supplementary information which was called for regarding the pupils tested. Their contribution was made in the interest of educational science, and without expectation of personal benefits of any kind. Their professional spirit cannot be too highly commended.