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http://www.newscientist.com/news/news.jsp?id=ns99996182

Yawning is catching in chimps 
 
00:01 21 July 04 
  
NewScientist.com news service 
  
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

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