In some circumstances, children of 5 produce identical classifications to 10 year olds when asked to sort a collection of objects. This has been interpreted as meaning that the process of constructing classifications is very similar at 5 and 10 years. But this conclusion rests on a comparison of the product of children's sortings, rather than on a study of their activity in producing sortings. The present paper argues that the process of classifying is in fact very different for 5 (...) and 10 year olds: whereas the older children treat the whole classification as a single unit composed of interrelated classes, the younger children proceed as though each class were independent of the others. At around 7 years, there is evidence for a transitional phase, in which children directly work on the relations between classes and so organize their initially “juxtaposed” procedures into more coherent systems. The tendency to work on the relations between elements in the process of classifying is not, however, simply an age‐related phenomenon: evidence for a similar effect can be observed in children throughout the age range of 5 to 10 years, during the course of short experimental sessions. Furthermore, the effect is not merely a response to errors or difficulties: the tendency to work on classifying relations can be seen in 5‐year‐old children in a task in which they are already successful. It seems that children spontaneously discover and use information about their procedures and the relations between them. This process is an end in itself. It occurs whether or not its results yield more successful performance. The approach taken in this paper is not confined to one area of behavior. This analysis of children's classifying fits closely with work in a very different domain, i.e. Karmiloff‐Smith's work on children's language and other representational systems. The analysis has implications for computer models of skill acquisition, as well as for psychological theories of development. (shrink)