Early evidence for emotional play contagion in juvenile ravens.

Perceiving, evaluating and reacting towards conspecifics' emotional states are important challenges of social group living. Emotional contagion describes an alignment of emotional states between individuals and is widely believed to be based on behavioral synchronization, i.e., behavioral contagion. As basic empathy-like processes, the occurrence of both forms of contagion seems to underlie early ontogenetic trajectories in humans and non-human species. In the present study, we assessed play as a context for studying the development of emotional contagion and its interlink with behavioral contagion in ten juvenile common ravens. Ravens are exceptional players that engage in all three forms of play: object, locomotion and social play. To assess potential ontogenetic patterns of both behavioral and emotional contagion, we tested juvenile ravens at two different periods of early development, at three- and six-month post-hatching. We elicited object play in one or several ravens (demonstrators) in a standardized experimental environment, using a playground setup. At both test ages, we found evidence for emotional contagion as observer ravens showed an increase of locomotion and social play after we provided the demonstrator(s) with the playground setup, but no significant changes in the amount of object play. Hence, observers did not copy motor patterns from demonstrator(s) but engaged in other forms of play. Our findings speak for a transfer of a general mood state in the context of play in ravens as young as 3 months and against behavioral mimicry as a precondition for emotional contagion.