Response facilitation in the four great apes: is there a role for empathy?
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Contagious yawning is a form of response facilitation found in humans and other primates in which observing a model yawning enhances the chance that the observer will also yawn. Because contagious yawning seems to be more easily triggered when models are conspecifics or have a strong social bond with the observer, it has been proposed that contagious yawning is linked to empathy. A possible way to test this hypothesis is to analyze whether individuals’ responses differ when they observe models yawning or performing different involuntary (i.e., nose wiping, scratching) and voluntary (i.e., hand closing, wrist shaking) actions that are not linked to empathy. In this study, we tested the four great ape species with two different setups by exposing them to a human experimenter repeatedly performing these actions online, and video-recorded conspecifics repeatedly performing these actions on a screen. We examined which behaviors were subject to response facilitation, whether response facilitation was triggered by both human models and video-recorded conspecifics, and whether all species showed evidence of response facilitation. Our results showed that chimpanzees yawned significantly more when and shortly after watching videos of conspecifics (but not humans) yawning than in control conditions, and they did not do so as a response to increased levels of anxiety. For all other behaviors, no species produced more target actions when being exposed to either model than under control conditions. Moreover, the individuals that were more “reactive” when watching yawning videos were not more reactive when exposed to other actions. Since, at least in chimpanzees, (1) subjects only showed response facilitation when they were exposed to yawning and (2) only if models were conspecifics, it appears that contagious yawning is triggered by unique mechanisms and might be linked to empathy.
KeywordsContagious yawning Chimpanzees Great apes Empathy Response facilitation
This work was funded by a SEDSU project (contract number 012-984 NESTPathfinder), funded by the European Community’s Sixth Framework Programme (FP6/2002–2006). The manuscript was written while Federica Amici held a Humboldt Research Fellowship for Postdoctoral Researchers (Humboldt ID Number 1138999). We thank all the animal keepers at Leipzig Zoo for their endless support and cooperation, Bahar Tuncgenc and Alex Sanchez for coding data for interobserver reliability purposes, and two anonymous reviewers for their very useful comments on a previous version of the manuscript. This study complies with the ethical standards as laid down by the Primate Society of Japan, and was ethically approved by an internal committee at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
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