Chimpanzees can “catch” yawns from humans as they grow older, a new study suggests.
Scientists studied the chimpanzees’ susceptibility to the yawning contagion -- already reported in humans, dogs and other non-primate species -- by yawning or imitating the action in front of 33 orphaned chimpanzees of varying ages. Even though the chimps were unfamiliar with the humans they interacted with, the juvenile primates imitated the human gesture while the infants did not, the Los Angeles Times reports.
The findings, published in the journal PLOS ONE, revealed that the chimps’ ability to empathize influences their susceptibility to “catch” yawns.
“I think we’re talking more about affective empathy,” Elainie Alenkaer Madsen, an evolutionary psychologist at Sweden's Lund University, told the Los Angeles Times. “It’s the kind of empathy where, instead of thinking your way into how someone else might be experiencing the world or feeling, you just feel it. Like when someone cuts their finger you feel sick in your stomach.”
Previous studies have shown that yawning isn’t always associated with being tired. In adult humans, chimpanzees, bonobos, baboons and dogs, contagious yawning may be used as a measure of empathy.
Much like humans, chimpanzees were found to catch yawns by the age of five, the study concluded. The study also proved that emotional closeness didn’t affect whether the chimps yawned or not.
"A reason for this may be that chimpanzees typically engage in competitive, even hostile, relationships with unfamiliar members of their own species, but rarely do so with humans, who they mostly experience as cooperative," Madsen said in a statement describing an explanation towards the phenomenon.
"Alternatively, it is possible that younger chimpanzees switch from a ‘generalized empathy’ to all individuals – irrespective of species – to a more ‘targeted empathy’ as they mature into adults and possibly have stronger reasons to differentiate friends from foes.”
Chimpanzees are not the only animals that catch yawns. In August, a Japanese study showed that when dogs witness a stranger or their owner yawn, they were more susceptible to imitate their owner’s actions.
“Our study suggests that contagious yawning in dogs is emotionally connected in a way similar to [the way it is in] humans,” study leader Teresa Romero of the University of Tokyo, said in a statement.
Researchers from the latest chimpanzee study expected similar results in their findings. “We really expected the adoptive mother of the chimps would be able to provoke more contagious yawning, with the younger chimps in particular,” Madsen explained. “But there was no such thing, which is puzzling.”
Madsen said researchers are still looking for answers on the reasons behind contagious yawning. “We do not have the full explanation yet, as it is a complex phenomenon that is being explored,” Madsen said.