_Age 15:_ 1. Repeats seven digits. 2. Finds three rhymes for a given word. 3. Repeats a sentence of twenty-six syllables. 4. Interprets pictures. 5. Interprets given facts. _Adult:_ 1. Solves the paper-cutting test. 2. Rearranges a triangle in imagination. 3. Gives differences between pairs of abstract terms. 4. Gives three differences between a president and a king. 5. Gives the main thought of a selection which he has heard read. It should be emphasized that merely to name the tests in this way gives little idea of their nature and meaning, and tells nothing about Binet's method of conducting the 54 experiments. In order to use the tests intelligently it is necessary to acquaint one's self thoroughly with the purpose of each test, its correct procedure, and the psychological interpretation of different types of response.[10] [10] See Part II of this volume, and References 1 and 29, for discussion and interpretation of the individual tests. In fairness to Binet, it should also be borne in mind that the scale of tests was only a rough approximation to the ideal which the author had set himself to realize. Had his life been spared a few years longer, he would doubtless have carried the method much nearer perfection. HOW THE SCALE IS USED. By means of the Binet tests we can judge the intelligence of a given individual by comparison with standards of intellectual performance for normal children of different ages. In order to make the comparison it is only necessary to begin the examination of the subject at a point in the scale where all the tests are passed successfully, and to continue up the scale until no more successes are possible. Then we compare our subject's performances with the standard for normal children of the same age, and note the amount of acceleration or retardation. Let us suppose the subject being tested is 9 years of age. If he goes as far in the tests as normal 9-year-old children ordinarily go, we can say that the child has a "mental age" of 9 years, which in this case is normal (our child being 9 years of age). If he goes only as far as normal 8-year-old children ordinarily go, we say that his "mental age" is 8 years. In like manner, a mentally defective child of 9 years may have a "mental age" of only 4 years, or a young genius of 9 years may have a mental age of 12 or 13 years. SPECIAL CHARACTERISTICS OF THE BINET-SIMON METHOD. Psychologists had experimented with intelligence tests for at least twenty years before the Binet scale made its appearance. The question naturally suggests itself why Binet should have been successful in a field where previous efforts had been for the most part futile. The answer to this question is found in three essential differences between Binet's method and those formerly employed.