Chimpanzees, like people, can "catch" yawns from others. But not all yawns are created equal, it seems; chimps are more likely to catch yawns from a chimp they know than from a stranger, a new study found. (You can see a video of it here.) This supports the idea that it's empathy---rather than just everybody needing a nap---that makes yawns contagious. How the Heck:
What's the News:
Two groups of chimps at the Yerkes National Primate Research Center near Atlanta, each with about a dozen adult members, were part of the study. The two groups lived in different large enclosures, and hadn't seen---much less gotten to know---each other. Chimpanzees are extremely territorial, and a whole lot friendlier to individuals in their own group than to strangers.
The researchers took videos of spontaneous yawns from chimps in each group, as well as videos of the chimps just hanging out in the enclosure. They then played each chimp two videos on an iPod Touch: a yawn video, which included clips of chimps from both groups yawning, and a control video, of chimps doing other things.
The chimpanzees yawned more when they saw their group members yawning than when they saw them going about their usual business, the study found, and they yawned more in response to their groupmates' yawning than to the yawns of chimps in the other group.
What's the Context:
Previous research with humans has linked the ability to feel empathy to catching a contagious yawn; The Thoughtful Animal blog provides a good explanation of this phenomenon.
Both very young children, who are still developing an understanding of others' state of mind, and children with autism, who are less attuned to what other people are feeling, seem to be immune to contagious yawns.
Reference: Matthew W. Campbell, & Frans B. M. de Waal. "Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy." PLoS ONE, 6 (4), 2011. DOI :10.1371/journal.pone.0018283
Image: Flickr / nilsrinaldi