One chimpanzee can convey to others, who have no other source of information, the presence, direction, quality, and relative quantity or preference value of distant hidden objects that he himself has not seen for several minutes. Exchange of information about objects and events probably requires no human training, or specialized ethological displays, or language.
One member of a social unit of 8 wild-born captive chimpanzees learned to gain access to elevated points such as windows and trees by using a pole as a bridge between two points. ‘Ladder making’ behavior soon spread across the rest of the group. In some cases 2 or more animals collaborated in setting up poles. This paper describes the developmental history and the social background of this behavior, and indicates its implications for theories of nonhuman tool-using.
Although no comparable behaviors have as yet been reported in wild chimpanzees, most captive chimpanzees easily learn to stand a loose branch or other elongated object vertically, and use it for vaulting or climbing. The present animals went beyond this: they also learned to brace the top of the branch against a vertical structure (wall, tree, etc.), and thus create a ‘ladder’ which would remain standing indefinitely and which could be used simultanously by several animals. An earlier paper described the origin and first varieties of ladder using; the present paper describes a new variety, namely escape over the 5.5 m high fence. No deliberate training was involved at any stage of our research.
A 30-minute film is shown, to illustrate some of the major effects of rearing upon the patterns of response of young chimpanzees.These films were made when the Ss were about 2 years old and were released for the first time into a strange bare room. All of the 27 Ss (and others, who do not appear in the film)responded to this situation with strong "emotional" reactions. But note the very different types of responses in different Ss, looking particularly for differences in posture, locomotion, manipulation of the environment, vocalization, and selfdirected acts such as thumbsucking, rocking, and swaying.The first 16 Ss in the movie were all raised from the day of birth until they were 21 months old in the "restricted" conditions of a small enclosed cage (Pix,
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