The fact that a dog is a man's best friend even applies when their sleepy, according to new research from Japan that shows canines are more likely to yawn along with their owners rather than with strangers.

Contagious yawning occurs in between 50 to 60 percent of adults, but surprisingly not babies, and the phenomenon has been linked to the activation of brain networks that control empathy and social skills.

Other animals participate in the social behavior too, such as chimpanzees, baboons, and macaques. Outside of primates, only parakeets (budgerigars) and dogs are known to subcumb to contagious yawning.

For this study, 25 dogs were observed while their owners or an unfamiliar person acted out yawning in front of them.

Dogs yawned nearly four times more with a familiar friend than with a stranger, suggesting cross-species empathy between canines and humans.

"Our study suggests that contagious yawning in dogs is emotionally connected in a way similar to humans," said Dr. Teresa Romero, a neuroscientist at the University of Tokyo. "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."

Source: Romero T, Konno A, Hasegawa T. Familiarity Bias and Physiological Responses in Contagious Yawning by Dogs Support Link to Empathy. PLoS One. 2013.