Development of manipulations with objects in ape and human infants

Abstract

Object manipulations were studied in infants (8–11 months of age) of three primate species: human; common chimpanzee ( Pan troglodytes ); and bonobo or pygmy chimpanzee ( Pan paniscus ). Observations of free play were videotaped and the complexity of manipulations (based on Piagetian theory) and functional usage of modes (both hands and feet) was described. Results indicated that the chimpanzee mouthed (without grasping) more frequently than both the bonobo and human infants. For all infants, half of the object-oriented behaviors consisted of active manipulations of a single object. However, for the apes, most of these manipulations consisted of simple holding and/or moving the objects against a substrate. In contrast, the human infant more frequently extracted an object from the background and, furthermore, moved the object or explored its unique characteristics. Additionally, the human infant exhibited a richness and differentation in the use of modes that was not observed in ape infants. These results are discussed within an evolutionary perspective.