The development of detour ability during infancy.

3 longitudinal studies were conducted to examine the generalization of detour ability across motor responses and barrier types and the relationship between the development of object permanence and detour ability. In Experiment 1, 12 8-month-olds were tested every 3 weeks for 4 months on 4 different detour problems and Stage 4 and 6 object permanence tasks. In the detour problems, infants had to reach or move around a transparent or opaque barrier to obtain an object. The results indicated that infants made reaching detours before corresponding locomotor ones and generally made detours around opaque barriers before transparent ones. Infants also solved the Stage 4 task before the detour problems but failed to solve the Stage 6 task before testing ended. The results of Experiments 2 and 3 suggested that the difference in reaching and locomotor detour performance was not an artifact of barrier length or the infant's position relative to the barrier. The overall results are discussed in relation to issues of developmental synchrony and Piaget's theory of infant spatial development.