Effects of IQ and mental age on hypothesis behavior in normal and retarded children

Mental-age-matched normal and retarded subjects at mental-age (MA) levels 5.5, 7.5, and 9.5 years received blank-trial discrimination problems designed to expose hypothesis behavior. There was evidence that subjects at all MA levels used hypotheses. Use of feedback indicating that a response was wrong increased significantly with MA, while use of feedback indicating that a response was right increased significantly with IQ. On simple problems involving two stimulus dimensions, retarded and normal groups used about equal numbers of hypotheses, but on four-dimensional problems the retarded used fewer hypotheses than normals. This IQ Level X Problem Complexity interaction may explain contradictions among previous findings regarding IQ effects on learning. A major issue in developmental psychology concerns the respective roles of rate of learning and level of cognitive development in determining intellectual performance. This issue has been especially central in research with familially retarded children. Views of cultural-familial retardation tend to cluster around two contrasting poles which Zigler (1969) has labeled developmental and difference theories. Difference theories ascribe specific intellectual deficiencies to the familially retarded (e.g., deficient attention and retention processes, cf. Zeaman, 1973; Zeaman & House, 1967), while Zigler's developmental view is that the cognitive competence of familially retarded persons should be essentially similar to that of mental-age-matched normals.