Current Biology
Volume 22, Issue 2, 24 January 2012, Pages 142-146
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Wild Chimpanzees Inform Ignorant Group Members of Danger

https://doi.org/10.1016/j.cub.2011.11.053Get rights and content
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Summary

The ability to recognize other individuals' mental states—their knowledge and beliefs, for example—is a fundamental part of human cognition and may be unique to our species. Tests of a “theory of mind” in animals have yielded conflicting results [1, 2, 3]. Some nonhuman primates can read others' intentions and know what others see, but they may not understand that, in others, perception can lead to knowledge [1, 2, 3]. Using an alarm-call-based field experiment, we show that chimpanzees were more likely to alarm call in response to a snake in the presence of unaware group members than in the presence of aware group members, suggesting that they recognize knowledge and ignorance in others. We monitored the behavior of 33 individuals to a model viper placed on their projected travel path. Alarm calls were significantly more common if the caller was with group members who had either not seen the snake or had not been present when alarm calls were emitted. Other factors, such as own arousal, perceived risk, or risk to receivers, did not significantly explain the likelihood of calling, although they did affect the call rates. Our results suggest that chimpanzees monitor the information available to other chimpanzees and control vocal production to selectively inform them.

Highlights

► Chimpanzees understand others' perceptual states, but do they understand knowledge? ► In a field experiment, subjects alarm called more with unaware than with aware others ► Calling was poorly explained by likely confounds, such as arousal or perceived risk ► We conclude that chimpanzees take receivers' state of knowledge into account

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These authors contributed equally to this work