Contagious yawning (i.e. yawning triggered by perceiving others' yawning) is a well-documented phenomenon, but the mechanism underlying it is still unclear. In this chapter, I review the current evidence about: (1) developmental studies with typically and atypically developing populations, and (2) comparative studies in non-human animals. Developmental studies have revealed that contagious yawning is disturbed in individuals with autism spectrum disorders, suggesting that contagious yawning may share a developmental basis with the capacity for theory of mind. Comparative studies have suggested that contagious yawning can be observed in non-primate species, such as domestic dogs. As dogs are known to have exceptional skills in communicating with humans, it has also been suggested that contagious yawning may be related to the capacity for social communication. These results from developmental and comparative studies are consistent with the claim that the mechanism underlying contagious yawning relates to the capacity for empathy.

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