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2 March 2011, 10:11 | Updated: 9 March 2011, 16:24
Chimpanzees mimic the laughter of their playmates even if they don’t find the situation funny, according to scientists at University of Portsmouth.
Research by Dr Marina Davila-Ross, has shown that the apes do not just ape the expressions of their social partners.
The psychologist said the chimpanzees appeared to use laughter to strengthen social bonds, just like humans.
She said this showed that great apes had a more complex social use of expressions than previously thought.
Dr Davila-Ross said: “Humans clearly use laughter as an important response in a wide range of social situations, but it is particularly interesting that chimpanzees seem to also use laughter to respond in such distinct ways.
“Great apes' ability to manage the sounds they make seems to be much more limited than humans and other animals, and even parrots.
“Nonetheless, their laughter might be partly managed and partly automatic.
“They do not just mimic the expressions of their playmates; they respond with their expressions in more complex ways than we were aware of before.
“We found their responsive laughter shows a similarity to the conversational laughter of humans.
“Both are shorter than spontaneous laughter and both seem designed to promote social interaction.
“These sorts of responses may lead to important advantages in co-operation and social communication - qualities that help explain why laughter and smiles have become integral tools of emotional intelligence in humans.”
The research, published in the journal Emotion, showed that responsive laughter in apes was shorter than compulsive laughter and prolonged play which has a vital role in the physical, emotional, social and cognitive development of both chimpanzees and humans.
The study also showed that compulsive laughter was evident at a younger age than responsive laughter.
Dr Davila-Ross's study examined laughter in 59 chimpanzees living in four groups in the chimpanzee sanctuary Chimfunshi Wildlife Orphanage in Zambia.
Two of the groups had been established for more than 14 years, and two groups had been living together for less than five years and all contained a mixture of ages and sexes.
Nearly 500 play bouts were video recorded and in all cases, playing sessions lasted significantly longer when one playmate joined in the laughter of another.
Dr Davila-Ross said that the laughter exhibited was not ‘fake laughter’, which was exclusive to humans, but simply the chimpanzee joining in with a playmate's laughter.
She added that the apes had to be part of the fun to start laughing and would not just laugh by hearing other apes laughing nearby.
Dr Davila-Ross said that laughter might have played an important part in human evolution.
She said: “Selection pressures might have favoured individuals who use their laughter in socially distinctive ways.
“The phenomenon of a laugh triggered by the laughter of others seems to be deeply rooted in primate evolution.
“In humans such laugh responses appear early in development. Apes and monkeys also copy the expressions of other apes, such as yawning and play faces.”
She added: “Five million years ago the ancestors of apes and humans must have produced laughter as rather honest social responses.
“Since then, the ability to control laughter must have drastically increased, along with its adaptive advantages, which explains why laughter has become a highly sophisticated, ubiquitous tool of co-operation and social communication in humans.”