An idiot, according to this classification, can not reach a degree of mentality beyond that of a normal child of three years, an imbecile beyond seven and a moron beyond twelve. This has been determined by means of a series of tests.
Mental and Physical Tests
There have been several attempts during the past fifteen years to formulate a series of graded tests which will evaluate children's span of intelligence and measure mental defects by means of comparison with posited norms. Binet has been at work longest trying to formulate such tests and with some success and while the Vineland and Lincoln institutions are adopting the Binet and Simon tests for work with feeble-minded children, the University Elementary School, of the University of Chicago, and the Psychopathic Institute, of the Chicago Juvenile Court, are establishing norms for normal American children.
Fig. 10. Psychometer. The psychic galvanometer or psychometer, which is used to detect delicate physiological changes which accompany the emotional experiences of children. This apparatus is also used in psychological methods for detecting crime, although the nature of the phenomena giving rise to the galvanometric deflections is still an open question.
The Binet and Simon tests throw little light on the moral or physical nature of the child, and they do not allow for sense defects, which would naturally affect a child's standing, even though normal in other respects. The latest edition of these tests takes into account the age of the child, and eliminates almost entirely the factor of training by measuring what the child learns fortuitously. They thus form a "measuring scale for intelligence" and are of direct value and interest to all parents and teachers of normal as well as backward or defective children. The fifty-seven tests cover the period from three to twelve years, and if a child succeeds in the tests derived for his age, he is normal; if he can succeed only in the test devised for a child one year
