You're more likely to catch a yawn from a relative than a stranger

Reading this blog post is likely to make you yawn. Not, hopefully, because it's boring, but rather because yawning is so contagious that even reading about it has been shown to provoke the behaviour. A popular theory for how yawns spread is that they automatically engage the empathy systems in our brains. Consistent with this, past research found that children with autism, some of whom have difficulty empathising, are immune to the contagious effects of yawns.

Now Ivan Norscia and Elisabetta Palagi have developed this line of enquiry, showing that we're more likely to catch a yawn from relatives than acquaintances, and more likely to catch them from acquaintances than strangers - presumably because we have more empathy for people with whom we're emotionally intimate.

The study was entirely observational. The researchers hung out in offices, restaurants, and waiting rooms and observed discreetly the yawning behaviour of the people about them. If one person yawned, the researchers waited to see if anyone else present yawned within the next three minutes. Data from one researcher was lost because they also caught the yawns and fell asleep (not really, I made that up). Sometimes the researchers knew the relationships of the people they were watching, other times they eavesdropped Bond-style on conversations to discern the social ties.

Of all the factors the researchers looked at, including things like the situational context and whether the yawner and their company were of the same nationality, it was only emotional closeness that was relevant. The closer, relationship-wise, a person was to the initial yawner, the more likely they were to yawn themselves. Emotional closeness was also associated with the number of times a yawn-catcher yawned, and the promptness with which they did so after being exposed to the precipitating yawn. Consonant with past research, it didn't matter if that precipitating yawn was seen or heard (one earlier study found that yawns are contagious even when they're "seen" non-consciously by people with damage to the visual part of their brains).

"The importance of social bond in shaping yawn contagion demonstrates that empathy plays a leading role in the modulation of this phenomenon," the researchers said. "Not only is contagion greater between familiar individuals, but it also follows an empathic gradient, increasing from strangers to kin-related individuals."

It's a hard life

Contagious yawning is also seen in monkeys and great apes. Indeed, this new study replicates similar findings with chimps, where the yawn contagion is greater between group members, and findings with baboons, for whom yawns are more often caught from intimate yawners (where intimacy is discerned from rates of mutual grooming). "When considered together," the researchers concluded, "these results suggest that the relationship between yawn contagion and empathy may have developed earlier than the last common ancestor between monkeys, humans and non-human apes."
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Norscia, I., and Palagi, E. (2011). Yawn Contagion and Empathy in Homo sapiens PLoS ONE, 6 (12) DOI: 10.1371/journal.pone.0028472

Post written by Christian Jarrett for the BPS Research Digest.