Why yawning is contagious in bonobos: As with humans, yawning Is more contagious when individuals are closely related

The researchers found that yawning in bonobos is more contagious when individuals are strongly bonded to one another as kin or close friends. They also found that yawn contagion was higher when individuals were more relaxed, but occurred in every context when the first yawner was a senior member of the group.

Previous research has found similar results in humans, showing that a person is more likely to yawn when family or close friends do, rather than in response to a stranger's yawning. Though this social component of yawn contagion is well-known, its origins and significance are still being studied.

Yawn contagion may be a way for social groups to unconsciously communicate and coordinate activities, but unlike other forms of unconscious communication, has a unique emotional component, since it appears to occur more frequently between closely bonded individuals. The authors say, "Though we are still far from a clear demonstration of a link between yawn contagion and empathy, the importance of social bonds in shaping this phenomenon in bonobos suggests that a basic form of empathy may play a role in modulating yawning behavior."