Is psychology suffering from an epidemic of “contagion”? Moving from metaphors to theoretically derived concepts and methods in the study of social influences

The term “contagion” has become increasingly popular as an omnibus catch-all to depict all kinds of mutual influences between people of equal status (or “peers”). We argue that some of these influences may qualify as “contagion,” but others denote alternative processes better described, for example, as exchange, transactions, or diffusion. To transform the term contagion from a loose metaphor to a precise and empirically useful concept, we propose that the paradigmatic case of contagious diseases can be used to identify multiple criteria that a social process must meet in order to qualify as contagion. Based on these essential elements, we describe the developmental signature of contagion, contrast contagion pathways with other temporal pathways of influence, and highlight empirical strategies needed to detect contagion. Finally, we conclude that interpretations about the nature of social influences and their labels should follow from (and not precede) empirical identification of the specific mechanisms that orchestrate transmission.