Three studies were conducted to investigate reasons for the difficulties that children under 5 years of age experience with class inclusion tasks. The studies tested the claim that such tasks have a structural complexity that is beyond the children's processing ability. In experiment 1, class inclusion tasks were compared with other classification…

The present study examines interrelations between young children's conceptions of similarity and difference prior to the operational coordination of these relations. A total of 24 preoperational children, 8 each at 3, 4, and 5 years of age, were tested with a classificatory task. Materials included four different geometrical shapes, with four…

The history of the study of human mental ability is an example of the dialectic in social science between those who interpret data within the framework of existing social inequities and those who look for perspectives that might eventually dissolve inequities. The dedication of Henry Herbert Goddard to a belief in the scientific proof of…