When is a stage not a stage? A critique of Piaget's theory of cognitive development and its application to science education

Summary Piaget's theory of cognitive development, in particular his ‘stage theory’, is having a significant influence on thinking about school science curricula. In the trend to more informal and child‐centred methods, his ideas have formed a base for many primary science programmes over the world.1 Until fairly recently, however, the impact of his thinking has not been felt in secondary science programmes. There are now signs that this is changing. The Piagetian model, particularly the stage theory, is being used in this country and elsewhere as both a scale on which to measure scientific development2 and an explanatory system to account for the difficulties secondary school pupils encounter in understanding scientific ideas.3, 4, 5 With this growing awareness of Piaget's work and its implications among secondary science teachers and curriculum developers perhaps it is timely to take a step back and review the status of the work critically. Since it is addressing itself to the relevance of Piagetian theory to learning science at the secondary school level, the focus of this paper is specifically on studies which relate to the development from concrete to formal level thinking. The first part outlines Piaget's general epistemological position and specification of the formal level of thought. This is followed by a discussion of three areas of problem with the Piagetian analysis: problems inherent in the specification of the logical model of formal thought; assumptions underlying Piaget's research methodology; and some problems with empirical findings. The second part of the paper comments on consequent problems in attempts to apply the Piagetian ideas to secondary science education. The paper ends by assessing the aspects of Piagetian work which may contribute to science education in the future.