The communicative context of object manipulation in ape and human adult-infant pairs

The communicative style of adult primates in relation to object manipulation in infants was examined in a pilot study involving three species of primates: human; common chimpanzee (Pan troglodytes); and bonobo, or pygmy, chimpanzee (Pan paniscus). Three areas of interest in this study were: (1) whether the adults acted on objects in a manner that served to engage the infants' attention with objects; (2) the effect of the adults' object manipulations on the infants' behavior with objects; and (3) whether certain behaviors of the infants consistently preceded the communicative actions of the adults. Results indicated that the adult apes rarely acted on objects with the apparent intent of engaging the attention of the infants. In contrast, adult humans primarily manipulate objects with the intent of stimulating, sustaining or enhancing the actions on objects by infants. Infant apes respond differnetially; they do not attend to the manipulations of adult apes, but they do attend to, and even manipulate, objects when interacting with an adult human. These results are discussed within the perspective of evolution and early human mother-infant interactions.