A longstanding and fundamental debate in developmental science is whether knowledge is acquired through domain-specific or domain-general mechanisms. To date, there exists no tool to determine whether experimental data support one theoretical approach or the other. In this article, we argue that the U- and N-shaped curves found in a number 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…