Professor John Drury, University of Sussex

Beyond contagion: How behaviour spreads – from yawning to riots

This talk is about one of the most powerful and persuasive metaphors in social science and everyday explanation: contagion. ‘Contagion’ usually translates as influence or spread of behaviour that occurs through mere touch, like a disease. The concept was first used in a social science context in the late nineteenth century when the crowd was seen as a threat to civilization and ‘gentlemen scholars’ sought intellectual weapons against that threat. Since then, numerous simple behaviours (such as smiling, scratching, and laughing) and complex phenomena (such as riots) have been described as cases of contagion. A key problem for all these accounts is the evidence of social group boundaries to influence – mere touch is not sufficient. Based on this evidence I suggest alternative ways of thinking about unintended influence in groups and crowds, based on the concept of shared social identity. I present examples from two lines of current research: first, experimental studies of the spread of simple behaviours (yawning) from individual to individual; second, a multi-method analysis of the spread of rioting across English cities in August 2011. In both cases, the concepts of shared identity and self-relevance help make sense of the patterns of behaviour. My take-home message is that the contagion concept conceals more than it reveals and that we need another terminology for talking about behavioural spread.

Keywords: contagion, social identity, social psychology, crowd behaviour