Spontaneous classification in action by a human-enculturated and language-reared bonobo (Pan paniscus) and common...

The authors investigated the formal features of spontaneous manipulations used by 1 bonobo (Pan paniscus) and 2 common chimpanzees (Pan troglodytes) to classify objects in action. Chimpanzees' manipulations were evenly split between serial, one-at-a-time acts on 1 object and parallel, two-at-a-time acts on 2 or 3 objects. Chimpanzees systematically combined their manipulations into routines to generate class-consistent categories of objects. Their routines featured much reproduction of the same manipulations, planful acts that anticipated follow-up manipulations, and manipulations that were reciprocal to each other to accomplish an end. In all these respects, chimpanzees' manipulations were similar to those of 2-year-old human infants. In others they differed. Chimpanzees' routines were mainly based on a linear integration of manipulations. Classifying in action was only infrequently produced by hierarchically integrated routines.