Yawning is contagious and this is proven by research that show people are likely to yawn if they see somebody else yawning. Findings of a new study, however, reveal that it isn't just in humans that yawning is infectious.

Primates such as chimpanzees are known to exhibit the contagious effect of yawning, but researchers from The University of Tokyo in Japan have found evidence that wolves also spread yawns among themselves.

For the new study published in the journal PLOS ONE on Aug. 27, Teresa Romero, from the Department of Cognitive and Behavioral Sciences of The University of Tokyo in Japan, and colleagues observed a pack of wolves at the Tama Zoological Park, a 129-acre zoo known for its naturalistic enclosures.

For more than five months, the researchers spend hours making observations and taking notes whenever a wolf yawned. They also recorded the response of the wolves that have seen the yawn as well as noted how many times the wolves yawned when they do not see their packmates yawning.

The researchers found that just like humans, wolves were more likely to yawn after they see another wolf yawning than at other times. The wolves were observed to yawn after seeing a wolf do so 50 percent of the time while wolves only yawned 12 percent of the time when they did not see another wolf yawning.

Earlier studies have shown that yawning tends to be more contagious among family members and loved ones, which suggests that people who spend more time together and share a special bond are more likely to be infected of each other's yawn. In the new study involving wolves, the researchers also observed a similar pattern. Romero and colleagues found that yawning tends to be more contagious in wolves who share close social bonds.

"The current study demonstrates that yawning in wolves is contagious and that, according to the empathy-based hypothesis, the strength of the social bond between the model and the subject correlated with the susceptibility to yawn contagiously," the researchers wrote.

Although yawning is a common phenomenon, the science behind what triggers the yawn remains unclear. Some scientists believe that yawning is a means to cool the brain while others theorize that it boosts alertness which could help explain why some individuals are likely to yawn when they are under stress. Most experts, however, agree that the reason why yawns are infectious is that humans are emphatic.