Abstract This article summarizes a number of recent findings and ideas concerning how children choose among existing strategies and how they discover new ones. Across a wide range of domains, individual children use diverse strategies. In all of these domains, they choose adaptively among the alternative approaches. Consistent individual differences are present within the strategy choices of both middle and lower class populations, and these predict performance on standardized achievement tests. The ideas about strategy choices have been formalized within running computer simulations that produce performance much like children's both in terms of performance at any one time and in terms of changes over time. The article concludes with a description of recent work on how children discover new strategies and with a discussion of the relation of the present perspective on cognitive development to that embodied in traditional Piagetian and neo-Piagetian theories.