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)

Surveys 30 studies involving 104 separate tests of the "similar structure hypothesis" which holds that, when nonorganically impaired retarded and nonretarded persons are similar in developmental level, they are also similar in the processes and concepts by which they reason. (Researchers distinguished between studies that excluded…