The spread of yawning among primates is not just an indicator of sleepiness or boredom. For chimpanzees it is also a sign of social connection between individuals , according to new research conducted at the Yerkes Primate Research Center at Emory University (USA). According to scientists, chimpanzees yawn more if they see someone from the same family or social group open their mouths than if they see a stranger yawn .
In an article published in the journal Public Library of Science One ( PLoS ONE ), Matthew Campbell and his colleagues suggest that the more a yawn infects a group of primates, the more empathy exists between them. Everything points, they say, that "yawning is contagious for the same reason as smiling, frowning and other facial expressions." " The contagion of yawning can be used as a visible measure of empathy ", that is, of the ability to perceive and share the experiences and emotions of other individuals, Campbell concludes.
