HIERARCHICAL COMPLEXITY OF COMBINATORIAL MANIPULATION IN CAPUCHIN MONKEYS (CEBUS-APELLA)

The purpose of this study was to examine the hierarchical complexity o f combinatorial manipulation in capuchin monkeys (Cebus apella). Two e xperiments were conducted. In Experiment 1 capuchins were presented wi th an apparatus designed to accommodate the use of probing tools. In E xperiment 2 the same capuchins were presented with sets of nesting con tainers. Five of the ten subjects used probing tools and seven subject s placed objects in the containers. The capuchins' behavior reflected three hierarchically organized combinatorial patterns displayed by chi mpanzees and human infants. Although the capuchins sometimes displayed the two more complex patterns (''pot'' and ''subassembly''), their co mbinatorial behavior was dominated by the simplest pattern (''pairing' '). In this regard capuchins may not attain the same grammar of manipu lative action that has been reported for chimpanzees and young human c hildren. (C) 1994 Wiley-Liss, Inc.