Persons representing the extremes of intelligence cannot be included in the same study unless they are approximately equated on mental age, in which case the relative performances of the extreme groups can provide useful information about the nature of intelligence. (Author/RD)

Reviews the major contributions of Alfred Binet. Explains why the fame of the Binet-Simon Intelligence Scale was so long lasting whereas that of his other contributions was so fleeting. Discusses implications of his contributions for current efforts to formulate unified theories of cognition and cognitive development. (Author/GLR)