de Waal’s interpretation of Chimp Yeroen’s theatrical play

Example 2
Yeroen hurts his hand during a fight with Nikkie. Although it is not a deep wound, we originally think that it is troubling hishim quite a bit, because he is limping. The next day a student, Dirk Fokkema, reports that in his opinion Yeroen limps only when Nikkie is in the vicinity. I konw Dirk as a keen observer, but this time I find it hard to believe him. We go to watch, and it turns out that he is indeed right: Yeroen walks past the sitting Nikkie from a point in fornt of him to a point behind him and the whole time Yeroen is in Nikkie's field of vision he honbbles pitifully, / but once he passed Nikkie his behavior changes and he walks normally again. For nealy a week Yeroen's movement is affected in this way whenever he knows Nikkie can see him.

INTERPRETATION. Yeroen was playacting. He wanted to make Nikkie believe that he had been badly hurt in their fight. The fact that Yeroen acted in an exaggerately pitful way only when he was in Nikkie's field of vision suggests that he know that his signals would only have an effect if they were seen; Yeroen kept an eye on Nikkie to see whether he was being watched. He may have learned from incidents in the past in / which he had been seriously wounded that his rival was less hard on him during periods when he was (of necessity) limping. (de Waal 2007:34-36)
source_comments in Japanese