The general conception is that chimps are smart, orangutans are dumber. But orangutans come with big surprises in many cases. It was proved that they have the same ability as chimps to learn the sign language. A new research shows that captive orangutans "play charades" to communicate with humans, pointing that the apes adjust the way they communicate to their audience. The orangutans intentionally repeated or changed hand gestures based on the success or failure of their previous 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 communication skills in apes, our closest relatives, could shed a light on how the early forms of human language emerged.

The research team presented six orangutans from two zoos with either a tasty treat or a rather repulsive food item. The apes relied on humans to get the food, so they had to employ gestures to signal their wishes to their human helpers. The orangutans pointed all their communication gestures-like pointing, waving and blowing raspberries-toward the tasty food.
Sometimes the helpers would "understand" and pass the desired food to the animals. In other cases they purposefully misunderstood the apes' requests and gave them just a part of the preferred food or the undesirable alternative.

When the treat was over, all but one of the orangutans stopped signaling entirely. Several of the apparently satisfied apes retreated into their cages. But the "misunderstood" apes kept on signaling to the experimenter, repeating gestures already employed. When they got completely misread, not receiving any of the desirable food, they avoided repeating already failed signals.

"The response showed that the orangutan had intended a particular result, anticipated getting it, and kept trying until it got the result," said co-author Erica Cartmill.

Such communication skills can be general amongst orangutans.

"There's no reason to assume that these six would have abilities that would be completely absent or completely unknown in other orangutans," said Robert Shumaker, director of orangutan research at the Great Ape Trust research center, not involved in this research.

"If you document these capacities in even a small number of individuals, I think that's very, very meaningful," he added.
The question is if this type of gesturing is found also among wild orangutans or if it's simply a behavior employed with humans.

"[It's] hard to detect [in the wild] without setting up a 'dumb audience' situation, as we did in the experiment. But we imagine it is very implausible that this whole subtle process developed in zoos and only for people. Let's be positive: This must be a basic part of orangutan communication." said Byrne.