Dog owners who claim their pets know their feelings may be on to something: A new study shows that canines yawn more in response to their owners' yawns than they do to strangers' yawns.
That suggests dogs are "emotionally connected" to people, study leader Teresa Romero of the University of Tokyo said in a statement.
Scientists already knew that dogs sometimes yawn when they see people yawn, but it was unclear if that was considered a form of empathy or mild stress, as yawning can be caused by anxiety.
So Romero and her team set up an experiment in which 25 pet dogs watched both their owners and strangers yawn or pretend to yawn. (Read about why people yawn.)
The team ruled out stress when researchers saw no significant differences in the dogs' heartbeats during the experiments, according to the study, published August 7 in the journal PloS ONE.
Not only did the dogs in the study yawn more in response to their owners' yawns, they also yawned less when they saw fake yawns from their owners or from strangers, suggesting they were exhibiting true contagious yawning.
In a similar study published last year, scientists found that people yawn more in response to the yawns of people they care about most.
In the case of people, scientists suspect that contagious yawning is a form of empathizing with people experiencing a feeling, which—in the case of yawning—usually means stress, anxiety, boredom, or fatigue.
Elisabetta Palagi, of the Institute of Cognitive Sciences and Technologies in Rome, noted that the study is the first time that scientists have shown contagious yawning occurring between different species.
"This could be the result of a long process of domestication," said Palagi, who wasn't involved in the study. (Also see "Dogs' Brains Reorganized by Breeding.")
"Once more," she said, the study "demonstrates that dogs are capable of empathic abilities toward humans."