Abstract
Humans favor others seen as similar to themselves (ingroup) over people seen as different (outgroup), even without explicitly stated bias. Ingroup-outgroup bias extends to involuntary responses, such as empathy for pain. However, empathy biases have not been tested in our close primate relatives. Contagious yawning has been theoretically and empirically linked to empathy. If empathy underlies contagious yawning, we predict that subjects should show an ingroup-outgroup bias by yawning more in response to watching ingroup members yawn than outgroup. Twenty-three chimpanzees (Pan troglodytes) from two separate groups watched videos of familiar and unfamiliar individuals yawning or at rest (control). The chimpanzees yawned more when watching the familiar yawns than the familiar control or the unfamiliar yawns, demonstrating an ingroup-outgroup bias in contagious yawning. These results provide further empirical support that contagious yawning is a measure of empathy, which may be useful for evolutionary biology and mental health.
Highlights
Humans (Homo sapiens) favor other humans seen as belonging to their own group over humans seen as belonging to different social groups, even in absence of explicitly stated bias [1,2]
During transcranial magnetic stimulation (TMS) human subjects watched videos of needles penetrating the hand of ingroup or outgroup members, defined by race [6]
The chimpanzees yawned more in response to the familiar yawns than the unfamiliar yawns, demonstrating ingroup-outgroup bias. This bias supports the hypothesis that empathy is the mechanism underlying contagious yawning
Summary
Humans (Homo sapiens) favor other humans seen as belonging to their own group (ingroup) over humans seen as belonging to different social groups (outgroup), even in absence of explicitly stated bias [1,2] These biases have been extended to differential brain activity during empathy for pain. Singer et al [3] interpreted these findings as humans sharing the affective or emotional aspect of pain with others, but not the physical sensation of pain Extending these findings to bias, two studies presented visuals of painful experiences to human ingroup and outgroup members (as defined by race) while using fMRI to examine brain activity [4,5]. The subjects responded with a greater empathic response toward the violet hand than the outgroup hand, yielding a pattern of ingroup . violet . outgroup
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
