Studies comparing the strengths and weaknesses of intellectually retarded and superior groups are reviewed, with particular attention given to studies in which these extreme groups were matched with each other on mental age. (Author)

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)

Retarded and borderline intelligence adolescents (MA 8-12 years) and nonretarded children (MA 6-12 years) were given logical problem solving tasks. Results showed a profound deficiency in low IQ individuals on certain tasks requiring foresight and logic; MA markedly overestimates the performance of these individuals relative to the performance of…