Humans are the only form of life on earth that uses written language. But plenty
of animals tell each other things using sounds or gestures. Scientists keep being
surprised by how well some animals can do this.
A team of scientists at St Andrews University in Scotland has just made a discovery
about how orangutans use gestures to get a message across. It’s very clever - almost
as if they are playing charades.
Along with bonobos, chimpanzees and gorillas, orangutans are the closest living relatives
to humans. Together they and we are known as “great apes”. Most of us don’t look
much like apes, but we do have a lot in common with them.
Captiveorangutans change the signals they are making, or repeat them, depending
on whether their audience 'got it' the first time, says Richard Byrne. This is just
what people do when they play charades.
The new research is published in 2 August issue of the journal Current Biology.
The orangutans were clearly working out if their audience understood them, says Professor
Byrne. This surprised the St Andrews University scientists.
In playing charades, we humans try to get our meaning across without words. We use
gestures. And we help our own team with hints about how well they are doing. This
is just what orangutans have now been found to do.
The experiment that showed this was set up by Erica Cartmill and Richard Byrne. Their
aim was to find out if orangutansintend to communicate with people through gestures.
This had already been found in chimpanzees.
The St Andrews experiment worked like this: The scientists presented captive orangutans
with two types of food. One was tasty to them; the other wasn't. Both could be reached
only with help from the humans.
There was another catch. The scientists sometimes pretended not to understand the
orangutans’ requests. So they would sometimes give them only half of the tasty treats.
Or they would hand over the yuckier food instead.
When the human didn't get it right the orangutans kept trying to make them understand.
They tried new gestures.
But when the humans seemed to partly understand, the apes narrowed down their range
of signals. They focused on gestures they had used already. They repeated them, just
as humans do in charades.
This showed that the orangutansintended a particular result, Cartmill says. They
realised when the humans didn’t get it and when they almost got it, she says.
In the first case they gave up on signals they'd used already. They tried new ones
to get the message across. In the second case "they tended to repeat the signals
that had already partially worked, keeping at it with vigour.
"The result is that understanding can be achieved more quickly.”