contagious yawning

Scientists at Emory University have discovered that chimpanzees demonstrate more contagious yawning when watching videos of familiar chimpanzees yawning than unfamiliar chimpanzees, demonstrating an ingroup-outgroup bias for this empathetic response.


Studies have shown that humans empathize more with individuals who are perceived as belonging to their own group (ingroup) over those belonging to different social groups (outgroups). This bias is unconscious and occurs even in the absence of explicit, or conscious bias.  For example, recent studies of brain patterns have shown that humans demonstrate different empathic responses to pain based upon group status.

Humans mimic facial expressions such as smiles and frowns as a social tool. Scientists have found that people may reflexively mimic the facial expressions of those belonging to their ingroup more consistently than those belonging to an outgroup. Contagious yawning may be the result of this type of empathetic response. Contagious yawning has been demonstrated in five mammalian species including, humans, chimpanzees, stumptail macaques, gelada baboons, and domestic dogs.

Scientists at Emory University hypothesized that if empathy is the mechanism behind contagious yawning, then contagious yawning will show the same biases as other measures of empathy, including an ingroup-outgroup bias.

To test this hypothesis, researchers showed 23 chimpanzees videos of either familiar or unfamiliar chimpanzees yawning and at rest, and then monitored them for yawning behaviour. Chimpanzees are highly territorial and exclude individuals from neighbouring communities, which makes all strangers outgroups by default.

The results demonstrated that individuals yawned more frequently when they watched videos of their ingroup yawning than they did when they watched videos of their ingroup doing other non-related activities, clearly demonstrating empathic yawning. Notably, when the chimps were shown videos of the outgroup yawning, they did not yawn more frequently than when watching control videos. The results clearly indicated that the chimpanzees were more likely to yawn when they saw videos of familiar chimpanzees yawning than unfamiliar chimpanzees, demonstrating an ingroup-outgroup bias.  Furthermore, the scientists noticed that the chimpanzees actually spent more time watching the videos of unfamiliar chimpanzees yawning, indicating that increased attention paid to ingroups was not the mechanism for the bias.

Scientists use contagious yawning to study empathy functioning because of it’s relevance to human mental health and evolutionary biology. The implications of this study go beyond the study of empathy and explore issues of human social structures, particularly ingroup-outgroup bias. This is important because it allows us to test whether human ingroup-outgroup bias is rooted in an evolved mechanism for assessing social closeness, familiarity, and group status.  Because humans share an evolutionary ancestor with chimpanzees, this study gives us further insight into the evolutionary mechanism of empathy, including how bias impacts empathy.


Written By: Lisa Borsellino, B.Sc.

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