ABSTRACT
Jean Piaget was by far the most important single figure of all those who have ever studied cognitive development. This chapter outlines some of the achievements and some of the pitfalls of the Piagetian theory of intelligence. It points out 'insights' and 'illusions' which are respectively valuable and dangerous to psychologists' study of cognitive development. The chapter presents some brief comments on some work that sought to investigate questions about the concurrence or sequencing of operations which Piaget's structural description suggests belong together. The operations in question belong to the concrete operations stage, which is generally the best studied. There is not, however, much relevant work, and there are good practical reasons for this. In the first place, different versions of the description of the development of concrete operations imply different degrees of concurrence of operations. In the second, making an accurate judgement of concurrence or sequence requires perfect diagnostic tests.
