Developmental Versus Difference Theories of Mental Retardation and the Problem of Motivation *

The point is made that the essential controversy concerning mental retardation in which Zigler has been engaged is not one between motivational and cognitive viewpoints. The theoretical argument is rather between two cognitive approaches: a developmental position, on the one hand, and a difference position, on the other. Both of these positions are described, and the differential predictions stemming from them are noted. The relevance to the developmental-difference controversy of the MA measure, motivational factors, and the two-group approach to mental retardation is discussed.