A note on the development of deferred imitation in enculturated juvenile chimpanzees (Pan troglodytes)

In recent years, imitation has played a central role in conceptions of children s memory, representational, and social cognitive abilities; in nonhuman primate cognitive competencies; and the evolution of human culture. In this paper, we combine data from three studies that assessed deferred imitation in three juvenile, enculturated (human-reared) chimpanzees (Pan troglodytes), administered over a 4-year period, to assess the development of deferred imitation. The basic task used in each study involved a baseline, followed by a demonstration in which a model displayed some actions on objects to participants. After a 10-min delay, the participants were given the objects and evidence of imitation was noted. The number of trials on which chimpanzees displayed deferred imitation increased with age, both between and within participants. Developmental differences were most apparent on the more complex tasks that required coordination of actions on materials (e.g., putting a nail in form board and striking it with a hammer) than on simpler tasks (e.g., striking two cymbals together). Patterns of performance were similar when the complete set of actions This paper was written while the first author was supported by a Research Award from the Alexander von Humboldt Foundation, Germany, and while working at the University of W€ urzburg, Germany. We express our appreciation to the Humboldt Foundation and to Wolfgang Schneider for their support of this work. Portions of this research were presented at the Conference on Human Development, Charlotte, NC, April, 2002. * Corresponding author. Fax: 1-561-297-2160. E-mail address: [email protected] (D.F. Bjorklund). 0273-2297/$ see front matter 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0273-2297(03)00021-2 390 D.F. Bjorklund, J.M. Bering / Developmental Review 23 (2003) 389–412 (targets) were duplicated by the ape and when the ape duplicated only portions of the demonstrated behavior (approximation to the target). The results were interpreted as reflecting age-related changes in chimpanzees abilities to engage in complex social learning after a delay, and arguably in the symbolic representational system supporting such abilities. 2003 Elsevier Science (USA). All rights reserved.