Infants ranging in age from six months to eight months were shown repeated instances of real object movement-disappearance-reappearance. Results suggest that the key changes in early cognitive development rest primarily upon the infant's gradual adaptation of old responses through encounters with new events--rather than upon the acquisition of…

Reviews "Levels of Cognitive Development," which presents a theory of cognitive development integrating discrimination- learning research with understanding of higher cognitive processes. Argues that strengths include its presentation of systematic research and providing continuity between past and present models. Weaknesses include…