A new study has discovered that dogs find their owner's yawns more contagious than the yawns of their canine counterparts.
This could be an indication of empathy from the animal long seen to be man's best friend, according to a group of researchers from the University of Tokyo.
A Japanese team of researchers recruited 25 dogs and their owners for the study and found that they were more likely to mimic the yawns of their masters than strangers because they are emotionally connected to their owners.
Dogs watched their owner, or someone they did not know, yawn or mimic yawning mouth movements.
Two cameras were used to record dogs' responses during the testing sessions. Owners called their dogs by name and then yawned, or made a yawning movement, after making eye contact.
Four test sessions lasting five minutes were conducted for each experimental condition involving a real or fake yawn by an owner or one of the researchers.
At the same time, the dogs' heart rates were monitored using a device strapped to their chests.
Lead scientist Dr Teresa Romero, from the University of Tokyo, said: "Our study suggests that contagious yawning in dogs is emotionally connected in a way similar to humans.
"Although our study cannot determine the exact underlying mechanism operative in dogs, the subjects' physiological measures taken during the study allowed us to counter the alternative hypothesis of yawning as a distress response.
"The occurrence of yawn contagion was significantly higher during the yawning condition than during the control mouth movements.
"Furthermore, the dogs yawned more frequently when watching the familiar model than the unfamiliar one demonstrating that the contagiousness of yawning in dogs correlated with the level of emotional proximity."
Dogs were also far more sensitive to genuine yawns, and yawned significantly less often after seeing fake movements.
One possible explanation for yawning is that it is a tension-releasing reaction to mild stress. But the fact that the dogs responded more to their owners' genuine yawns, and maintained a constant heartbeat, made this unlikely, said the researchers.
Writing in the online Public Library of Science ONE, they said: "Our findings are consistent with the view that contagious yawning...may indicate that rudimentary forms of empathy could be present in domesticated dogs."
Contagious yawning is said to affect 45 per cent to 60 per cent of human adults, but the reason for this reaction remains unclear.
In non-human primates, the phenomenon has been observed in chimpanzees, bonobos, and gelada baboons. Like humans, they are more responsive to yawns from individuals they have close social bonds with.
Additional reporting by PAReuse content