Commentary on : ‘ ‘ Piaget ’ s stages : the unfinished symphony of cognitive development ’ ’ by D . H . Feldman

Dr. Feldman’s paper constitutes a worthy continuation of the select pedigree of thorough neo-Piagetian theory constructions. It presents a general theory of stagewise cognitive development, in the spirit of Piaget’s naturalized epistemology. Theory construction at the general level at which Piaget operated has, for good reasons, an essential place in cognitive developmental psychology. In particular theories of stagewise cognitive development have wide-ranging theoretical, methodological and practical implications. Any theory of stagewise development involves the specification of stages, periods of relatively stable performance of the developing system. Each stage is characterized as a re-identifiable qualitative whole, having a unique identity that can be named (by means of attaching labels). In this sense a stage is akin to a latent class in psychometrics (cf. van der Maas, 1998). In addition the theory should specify the sequence or sequences of allowed stage transitions. The duration of a stage transition is always negligible relative to the duration of stages (sudden transition). Hence stagewise development as described up to this level consists of a sequence or sequences of punctuated latent class transitions. In this sense stagewise development is akin to the hidden Markov process model in psychometrics (cf. Visser, Raijmakers, & Molenaar, 2000).