For most people, witnessing a yawn — or even thinking about yawning — creates an irresistible urge to yawn, too. And contagious yawning, it turns out, is yet another feature we share in common with many species of primates.
To investigate hypotheses about the cause of the phenomenon, Italian researchers looked at a group of 12 captive bonobos, which are highly social animals that cultivate strong relationships. Recent research also found that bonobo brains are relatively well developed in an area that detects distress in themselves and in others.
Over three months of observation, the researchers recorded more than 1,100 yawns among the bonobo adults. After each yawn, observers recorded whether another animal yawned over the next three minutes. In total, the researchers recorded nearly 300 contagious yawns.
Like in humans, the researchers report today in the journal PLoS One, most contagious yawns occurred within a minute after the original yawn.
The closer two animals were to each other socially, the more likely they were to catch yawns from each other. And female bonobos produced more contagious yawns than males did. The results support the theory that contagious yawning is a form of empathy that is deeply rooted in our evolutionary history.
"Even though we are still far from a clear demonstration of a linkage between yawn contagion and empathy, the importance of social bonds in shaping bonobo yawn contagion seems to support the hypothesis that a basic form of empathy can play a role in the modulation of this phenomenon," the researchers wrote.
"The higher frequency of yawn contagion in presence of a female as a triggering subject supports the hypothesis that adult females not only represent the relational and decisional nucleus of the bonobo society, but also that they play a key role in affecting the emotional states of others."
Photo: Like humans, bonobos yawn contagiously, but yawns are only infectious between close friends or kin. Credit: Elisa Demuru