Chimpanzees help each other upon request

Shinya Yamamoto, Tatyana Humle, Masayuki Tanaka
DOI: 10.1371/journal.pone.0007416
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Figures from the article

The apparatus and setup for experiment 1: view from outside the booths.
In this picture, the stick-use situation was set up in booth A, and the straw-use situation was set up in booth B. A straw was supplied to booth A, but could be effectively used only by the chimpanzee in booth B. A stick was supplied to booth B, but could be effectively used only by the chimpanzee in booth A. In the actual procedure, the tools (a straw and a stick) were supplied in the booths (not presented outside the booths as depicted here), and the partition of booth B was closed (not partially opened as depicted here).

Figure 2. Tool transfer upon recipient's request.
A chimpanzee (Mari) in the near-side booth picks up a stick and hands it over to her partner (Pendesa) in the far-side booth who requested the tool by poking her arm through the hole between the booths.

Article Information
Yamamoto S, Humle T, Tanaka M(2009)Chimpanzees help each other upon request PLoS ONE, 4 (10): e7416. https://dx.doi.org/10.1371/journal.pone.0007416
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