(IQ), index of intelligence determined through a subject's answers to arbitrarily chosen questions. The IQ is merely a standard score that places an individual in reference to the scores of others within his or her age group. Mental age represents the age level corresponding to the score reached on the test. Thus, if a child 10 years old gives a test score appropriate to that of the average 12year-old child, his or her mental age would be 12 and his or her IQ is 120. This method works reasonably well for younger children but has grave disadvantages when applied to older children or adults. In psychological literature, the following classification is found:
|Above 140||“Near” genius or genius|
|120–140||Very superior intelligence|
|50–70||Educable mentally retarded|
|20–30||Severely mentally retarded|
See also: Binet, Alfred.