http://www.guardian.co.uk/science/2007/dec/12/animalbehaviour?gusrc=rss&feed

Ian Sample, science correspondent
December 12 200

Research showing that orang-utans find laughter contagious has shed light on the evolution of empathy and its importance for animals that live in groups.

Researchers led by Marina Davila Ross, a psychologist at Portsmouth University, took video footage of pairs of orang-utans aged two to 12 playing at four primate centres around the world.

They recorded 31 orang-utans in 432 bouts of play, during which the orang-utans grappled, swung punches and occasionally tickled each other. When they caught an ape displaying a gaping mouth, the equivalent of laughter, they checked the response of its playmate. Often, the second orang-utan adopted the same expression less than a second later, suggesting the mimicry was an involuntary display of empathy.

"It shows how important this form of emotional communication is," said Davila Ross, whose study appears in the journal Biology Letters. "Empathy helps one communicate with social partners ... It helps form social bonds and it's supportive in terms of cooperation