This release is available in German.
Many animals produce alarm calls to predators, and do this more often when kin or mates are present than other audience members. So far, however, there has been no evidence that they take the other group members' knowledge state into account. Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and the University of St. Andrews, Great Britain, set up a study with wild chimpanzees in Uganda and found that chimpanzees were more likely to alarm call to a snake in the presence of unaware than in the presence of aware group members, suggesting that they recognize knowledge and ignorance in others. Furthermore, to share new information with others by means of communication represents a crucial stage in the evolution of language. This study thus suggests that this stage was already present when our common ancestor split off from chimps 6 million years ago.
The ability to recognize another individuals' knowledge and beliefs may be unique to humankind. Tests of a "theory of mind" in animals have been mainly conducted in captivity and have yielded conflicting results: Some non-human primates can read others' intentions and know what others see, but they may not understand that, in others, perception can lead to knowledge. When there are negative results, however, the question remains whether chimpanzees really cannot do the task or whether they simply do not understand it. "The advantage of addressing these questions in wild chimpanzees is that they are simply doing what they always do in an ecologically relevant setting", says Catherine Crockford, a researcher at the University of St. Andrews.
Catherine Crockford, Roman Wittig and colleagues set up a study with wild chimpanzees in Budongo Forest, Uganda. They presented them with models of dangerous venomous snakes, two
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