This book uses the paradigm of the child as a problem solver to examine various theories of cognitive development. * Provides balanced coverage of a broad range of contemporary theories. * Focuses on collaborative tasks which are carried out with other children or adults. * Asks whether social interaction is the key to improvement in problem solving skills, or whether it is the skills and abilities that the child brings to the task that are paramount. * Draws on a wide range of research, including the author's own research into dyadic problem solving.