Boredom, tiredness, hunger and stress can all set off a yawn. People can even âcatchâ a bout of yawning when they see or hear another person in the throes of the involuntary gesture, a phenomenon known as social yawning.
Researchers speculate that this shared behavior is a form of empathy that strengthens the bonds of a group: One drowsy personâs yawn that triggers others to do the same could lead to a unanimous call for bedtime, for example. Humans arenât the only species to yawn sympathetically: Dogs yawn in response to human yawns, and chimpanzees and baboons yawn in concert with one another.
Children with autism apparently donât respond to social yawning, however, prompting some researchers to blame their well-chronicled struggle with empathy.
A new Japanese study suggests that, instead, children with the disorder miss facial cues, such as closed eyes, that make yawning contagious. The study was published 22 July in Autism Research and Treatment.
The researchers say children with autism miss those cues because they avoid looking at peopleâs faces. But that may not entirely explain it. For example, a small 2009 study found that typically developing children yawn even when theyâve only heard another person do so, but children with autism do not.