Chimpanzees' Constructional Praxis (Pan paniscus, Pan troglodytes).

This study investigated chimpanzees' spontaneous spatial constructions with objects, and especially their ability to repeat inter-object spatial relations, which is basic to understanding spatial relations at a higher level than perception or recognition. Subjects were six chimpanzees, in fact four chimpanzees and two bonobos, aged 6 to 21 years, all raised in a human environment from an early age. Only minor species differences, but considerable individual differences were found. The effect of different object samples was assessed through the comparison with a previous study. A common overall chimpanzee pattern was also found. Chimpanzees repeated different types of inter-object spatial relations such as insertion (I), or vertical (V), or next-to (H) relations. However chimpanzees repeated I or V relations with more advanced procedures than when repeating H relations. Moreover, chimpanzees never repeated combined HV relations. Compared to children, chimpanzees showed a specific difficulty in repeating H relations. Repeating H relations is crucial to represent and understand multiple reciprocal spatial relations between detached elements and to coordinate independent positions in space. Therefore, the chimpanzees' difficulty indicates a fundamental difference with humans in constructive space. The findings are discussed in relation to issues of spatial cognition and tool use.