The findings were published online June 4 in the journal Current Biology.
"This is a very nice study which shows that when we sometimes compare the primate playface with laughing, we're actually correct," said Frans B.M. de Waal, a professor of primate behavior at Emory University, in Atlanta. "Some critics have argued that such terminology is anthropomorphic or that human laughing is a unique display in the animal world. But, in fact, there is a homology not just based on the facial expression, which we have suspected since Darwin, but also in the details of the breathing patterns and sounds of the display."
The study did not examine what -- if any -- connections exist between ape laughter and the development of humor, or precisely why the sounds evolved from short bursts into the voiced laughter of humans. In a surprising finding, however, gorillas and bonobos were able to make laughter sounds while exhaling longer than expected. This ability was thought to be unique to humans and to have played an important role in the evolution of speech, the researchers said.
Scientists not involved with the research said they were intrigued by the study and predicted it would contribute to the evolving view of primates, especially those in captivity.
"This kind of behavior does not surprise me," said Diana Reiss, professor of cognitive psychology at Hunter College in New York City, and an expert in animal communication. "We're finding many continuities between humans and the great apes. You see these behaviors and you see something you can relate to."
The late comedian John Belushi, star of Saturday Night Live and the movie Animal House, probably would have agreed.
To learn more about primate behavior, visit the Yerkes National Primate Res
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