ABSTRACT
As we have seen, my chimpanzees learn to balance long objects on their heads and faces when they are very young. The chimpanzees do this for fun but it is another simple technique for fi nding out if the stick is truly straight. Straight sticks balance differently from bent sticks. These techniques are part of an entire and systematic repertoire of tests chimpanzees perform upon a novel object, including tasting it, sniffi ng it and looking at it from different angles. This, in fact, is the general sequence in which chimpanzees conduct their sampling (often interspersed with bashing it or bashing something else with it), though the order and type of tests to which a novel object is subjected varies, depending on the age and experience of the chimpanzee and the type of object being investigated. (Of interest is that I do not see young Rah using such clear techniques for obtaining foreshortened views, even at the end of my 3 years with the chimpanzees, suggesting its use has a developmental and learning dimension.) Experienced chimpanzees recover two, key views of a straight stick of great value when navigating through an arboreal environment. These two aspects of a long object are very different from each other. Looking at a stick laterally, or ‘side-on’ to its length, reveals its saliently long axis which looks like a straight line, whilst looking at the stick from its end (‘end-on’) offers the very different image of a little spot or circle. Other forms of object offer up very different optical shapes. When Rah manipulates her lump of clay, for example, the shape it presents to the eye remains roughly the same, whichever way she looks at it, as a form extended roughly equally in all dimensions as John Willats (1997, 2005) would say, or, in a word, a ‘lump’. Rah’s lump of clay, can be tasted, sniffed and looked at but it is harder to wave around and, unlike a stick, cannot be pointed.
