Study title

Research into ‘contagion’ has been applied to a range of different behaviours. However, the failure to explain the apparent group-boundaries present in ‘passive’ social influence invites an explanation for behaviours incorporating social identification. In an online study aimed at investigating the role of social influence in the spread of contagious behaviour: scratching. Participants were presented with a video of a man identified as Scottish scratching or not scratching. The participants’ level of social identification with the scratching target was manipulated so that they viewed the actors as belonging to either an ingroup (British) or outgroup (English). Scratching by participants was both observed using a webcam and measured with a self-reported itchiness questionnaire. There was a significant main effect of video (scratch/neutral) on self-reported itchiness but no significant main effects or interaction of identity (IG/OG/undefined) or video (scratch/neutral) for shared identity, self-relevance, number of scratches, scratch duration or time to first scratch. For the scratching conditions, shared identification significantly predicted self-report itchiness (controlling for Emotional ‘Contagion’ trait and Gender). All indirect models were non-significant. In the scratching video condition there was moderated mediation such that strength of identification moderated the effect of Condition (IG/OG) on shared identification, which in turn mediated the effect of condition on self-reported itchiness.How and why do behaviours spread from person to person? In particular, how does aggression and violent behaviour spread? When, as in 2011, riots began in London, why did they then occur in Birmingham, Manchester, and Liverpool? One of the most common ways of addressing such issues is through the notion of 'contagion'. The core idea is that, particularly in crowds, mere exposure to the behaviour of others leads observers to behave in the same way. 'Contagion' is now...