Emotional contagion and prosocial behaviour in fish: An evolutionary and mechanistic approach.

In this review, we consider the definitions and experimental approaches to emotional contagion and prosocial behaviour in mammals and explore their evolutionary conceptualisation for studying their occurrence in the evolutionarily divergent vertebrate group of ray-finned fish. We present evidence for a diverse set of fish phenotypes that meet definitional criteria for prosocial behaviour and emotional contagion and discuss conserved mechanisms that may account for some preserved social capacities in fish. Finally, we provide some considerations on how to address the question of interdependency between emotional contagion and prosocial response, highlighting the importance of recognition processes, decision-making systems, and ecological context for providing evolutionary explanations. • Emotional contagion can explain ancestral forms of prosocial behaviour in fish. • The testable basis is state transfer triggering appropriate benefit from others' acts. • Recognition processes are a paramount component to elucidating this link. • Comparative approaches can reveal evolutionary substrates for higher-order functions. [ABSTRACT FROM AUTHOR]