for National Geographic News
Captive orangutans "play charades" to communicate with humans, a behavior that suggests the apes tailor their gestures to their audiences.
In a new study, researchers observed orangutans intentionally repeating or modifying hand gestures based on the success or failure of their first communication attempts.
"It was known that orangutans, like all great apes, are able to acquire new gestural signals," said study co-author Richard Byrne, an evolutionary psychologist at the University of St. Andrews in Scotland.
"But the charades analogy—implying that the animal is not only communicating as best it can but also picking up on the level of understanding of its audience and modifying subsequent gestures accordingly—is new information."
Understanding how apes, our closest genetic relatives, communicate could provide insight into the strategies that helped shape early forms of human language.
(Related: "Chimp 'Dinner Conversation' Proof of Ape Speech?" [October 20, 2005].)
The study appears this week in the journal Current Biology.
Byrne and his St. Andrews colleague Erica Cartmill presented six captive orangutans from two different zoos with either a tasty treat or a not-so-tempting food item.
The orangutans could only obtain the food with human help, so they needed to use gestures to communicate their wants to their helpers.
During the experiment, the orangutans directed all their communication attempts—such as pointing, waving, and blowing raspberries—toward the desirable food.
Sometimes the researchers would "understand" and give the animals the treat.
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