Supplementary material from "Contagious yawning is not a signal of empathy: no evidence of familiarity, gender or prosociality biases in dogs"

Contagious yawning has been suggested to be a potential signal of empathy in non-human animals. However, few studies have been able to robustly test this claim. Here, we ran a Bayesian multi-level reanalysis of six studies of contagious yawning in dogs. This provided robust support for claims that contagious yawning is present in dogs, but found no evidence that dogs display either a familiarity or gender bias in contagious yawning, two predictions made by the contagious yawning–empathy hypothesis. Furthermore, in an experiment testing the prosociality bias, a novel prediction of the contagious yawning–empathy hypothesis, dogs did not yawn more in response to a prosocial demonstrator than to an antisocial demonstrator. As such, these strands of evidence suggest that contagious yawning, although present in dogs, is not mediated by empathetic mechanisms. This calls into question claims that contagious yawning is a signal of empathy in mammals.