HOW THE SCALE WAS DERIVED. The tests were arranged in order of difficulty, as found by trying them upon some 200 normal children of different ages from 3 to 15 years. It was found, for illustration, that a certain test was passed by only a very small proportion of the younger children, say the 5-year-olds, and that the number passing this test increased rapidly in the succeeding years until by the age of 7 or 8 years, let us say, practically all the children were successful. If, in our supposed case, the test was passed by about two thirds to three fourths of the normal children aged 7 years, it was considered by Binet a test of 7-year intelligence. In like manner, a test passed by 65 to 75 per cent of the normal 9-year-olds was considered a test of 9-year intelligence, and so on. By trying out many different tests in this way it was possible to secure five tests to represent each age from 3 to 10 years (excepting age 4, which has only four tests), five for age 12, five for 15, and five for adults, making 54 tests in all. LIST OF TESTS. The following is the list of tests as arranged by Binet in 1911, shortly before his untimely death:-- _Age 3:_ 1. Points to nose, eyes, and mouth. 2. Repeats two digits. 3. Enumerates objects in a picture. 4. Gives family name. 5. Repeats a sentence of six syllables. _Age 4:_ 1. Gives his sex. 2. Names key, knife, and penny. 3. Repeats three digits. 4. Compares two lines. _Age 5:_ 1. Compares two weights. 2. Copies a square. 3. Repeats a sentence of ten syllables. 4. Counts four pennies. 5. Unites the halves of a divided rectangle. _Age 6:_ 1. Distinguishes between morning and afternoon. 2. Defines familiar words in terms of use. 3. Copies a diamond. 4. Counts thirteen pennies. 5. Distinguishes pictures of ugly and pretty faces. _Age 7:_ 1. Shows right hand and left ear. 2. Describes a picture. 3. Executes three commissions, given simultaneously. 4. Counts the value of six sous, three of which are double. 5. Names four cardinal colors. _Age 8:_ 1. Compares two objects from memory. 2. Counts from 20 to 0. 3. Notes omissions from pictures. 4. Gives day and date. 5. Repeats five digits. _Age 9:_ 1. Gives change from twenty sous. 2. Defines familiar words in terms superior to use. 3. Recognizes all the pieces of money. 4. Names the months of the year, in order. 5. Answers easy "comprehension questions." _Age 10:_ 1. Arranges five blocks in order of weight. 2. Copies drawings from memory. 3. Criticizes absurd statements. 4. Answers difficult "comprehension questions." 5. Uses three given words in not more than two sentences. _Age 12:_ 1. Resists suggestion. 2. Composes one sentence containing three given words. 3. Names sixty words in three minutes. 4. Defines certain abstract words. 5. Discovers the sense of a disarranged sentence.