For bonobos, yawning is contagious, but only between friends.
Yawns spread more easily between family and close friends, and from high-status monkeys to those lower on the totem pole, according to a study published online in the journal PLoS ONE. This pattern of social yawning mimics one found in humans and suggests infectious yawning is a byproduct of empathy, which coordinates emotions in a group.
"It underlines that the mechanism of yawn contagion in the two species is the same," said study co-author Elisabetta Palagi, a primate researcher at the University of Pisa in Italy. "One of the possible functions of yawn contagion is to synchronize individuals of a social group. In humans, yawn contagion is extremely important but just between people who share strong bonds."