Yawning is catching in chimps

Chimpanzees yawn in response to seeing other chimps yawn, reveals a new study. The discovery bolsters the idea that chimps are able to understand their own and others' state of mind.

Catching a glimpse of a colleague yawning during an important meeting is enough to have most humans fighting to stifle a gape.

And the impression that yawning is "contagious" has stood up to scientific scrutiny. When adult humans are shown videos of yawns, around 42 to 55 per cent also begin yawning.

Why humans do it is still controversial, although one suggestion is that it may have evolved as a social cue to synchronise sleep amongst a group.

Now a research team led by James Anderson at the University of Stirling in the UK has shown that chimpanzees also perform "contagious yawning".

Open-mouth behaviours

The team played videos of chimps either yawning or exhibiting other open-mouth behaviours such as grinning to six adult chimps and three infants at the Primate Research Institute of Kyoto University in Japan.

Two of the adults increased their yawning frequency considerably in response to the yawning video, while there was no difference with the others. "These data are highly reminiscent of the contagious yawning effects reported for human," the authors write in Biology Letters. They argue that their figure of 33 per cent of adults showing contagious yawning compares well with humans since the chimps do not understand the purpose of the trial.

The study is "superb" says Gordon Gallup, an evolutionary psychologist at the State University of New York in Albany who has worked on yawning in humans. He believes that it adds to evidence supporting the notion that chimps are capable of understanding the minds of others.

Adult infant split

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	Related Stories   Young female chimps outlearn their brothers 14 April 2004   Monkey business reveals sense of fair play 17 September 2003   Orangutans swinging culture revealed 02 January 2003     For more related stories search the print edition Archive     Weblinks   Primate Research Institute, Kyoto University, Japan   Evolutionary Psychology, State University of New York, Albany   Biology Letters

In research on people, those subjects that perform contagious yawning also recognise images of their own faces and are better at inferring what other people are thinking from their faces. What is more, brain imaging studies have shown that people watching others yawning have more activity in parts of the brain associated with self-information processing.

"Our data suggest that contagious yawning is a by-product of the ability to conceive of yourself and to use your experience to make inferences about comparable experiences and mental states in others," Gallup told New Scientist.

The adult infant split is also informative. Human infants do not start to recognise themselves in mirrors until they are 2 years old and they also do not yawn contagiously.

Journal reference: Biology Letters (DOI 10/1098/rsbl.2004.0224)

James Randerson