If watching other people yawn makes you yawn in response, don't chalk it up to empathy.
Contagious yawning is well documented and occurs in response to seeing, thinking or hearing about yawning. It's different than spontaneous yawning, which is linked with being tired or bored.
Some studies have suggested an association between yawning and empathy, but this new research found that contagious yawning may decrease with age and is not strongly associated with empathy, tiredness or energy levels.
The Duke University researchers came to their conclusions after recording the number of times that 328 healthy people yawned while watching a three-minute video of people yawning.
Some participants were more susceptible to contagious yawns than others, with the number of yawns per person ranging from zero to 15, according to the study published March 14 in the journal PLOS ONE.
Age was the only independent factor that significantly influenced contagious yawning. The older the person, the less likely they were to yawn while watching the video. However, age explained only 8 percent of the differences in the participants' responses to the video, the researchers said.
"The lack of association in our study between contagious yawning and empathy suggests that contagious yawning is not simply a product of one's capacity for empathy," study author Elizabeth Cirulli, an assistant professor of medicine at the Center for Human Genome Variation at Duke University School of Medicine, said in a university news release.
The researchers noted that contagious yawning is less common in people with autism or schizophrenia, and that learning more about the biology behind contagious yawning could help improve understanding about those disorders.