This study was designed to investigate the role of social influence on the transmission of behaviour. The study was carried out online and compared the degree to which the transmission of yawning behaviour between an actor, presented in a video, and participants was influenced by social identity; in this case, gender. There were significant main effects of ingroup/outgroup on shared identity and social identification, but not the dependent variables. Shared identity significantly predicted urge to yawn but not self-report or observed yawns. There was a significant serial moderated-mediation (Condition – [ID] – Shared Identity – Urge to Yawn – Observed Yawns). The model was also significant if observed yawns swapped for self-reported number of yawns, total duration of yawning, or time to first yawn. 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 used to explain everything from 'basic' responses such as smiling and yawning (where the mere act of witnessing someone yawn or smile can invoke the same response in another) to complex phenomena like the behaviour of financial markets and, of course, rioting. What is more, laboratory experiments on the 'contagion' of simple responses (such as yawning) serve to underpin the plausibility of 'contagion' accounts as applied to complex phenomena (such as rioting). Despite this widespread acceptance, the 'contagion' account has major problems in explaining the spread of behaviours. In particular, there are boundaries to such spread. If men smile at a sexist joke, will feminists also smile in response to the men's smiles? If people riot in one town, why is it that they also riot in some towns but not others? For example, in 2011, disturbances spread from London to Birmingham, Manchester and Liverpool but they did not spread to Sheffield, Leeds or Glasgow. 'Contagion' explanations cannot answer such questions because they assume that transmission is automatic. They do not take account of the social relations between the transmitter and receiver. We propose a new account of behavioural transmission based on the social identity approach in social psychology. This suggests that influence processes are limited by group boundaries and group content: we are more influenced by ingroup members than by outgroup members, and we are more influenced by that which is consonant with rather than contradictory to group norms. The social identity approach is therefore ideally suited to explaining the social limits to influence, both for 'basic' phenomena and rioting. In order to advance both theoretical understanding and practical interventions, our research will develop a social identity analysis of transmission processes at multiple levels. Accordingly, the aims and objectives of this research project are as follows: First, we will conduct a series of experimental studies on 'basic' behaviours (yawning, itching) to examine whether the effects of being exposed to a behaviour depend on observers and actors being fellow ingroup members. We will also examine 'complex' behaviours (aggression and rioting) to see if (1) observers are more influenced when the actors are ingroup members; (2) observers are more influenced by the responses of other observers when these are also ingroup members; (3) willingness to copy others depends upon whether their behaviour is consonant with observer group norms. Second, we will examine the spread of urban disorder during the 2011 English riots. We have been granted special access to the full data-set from the Guardian/LSE 'Reading the Riots' study (270 interviews with participants carried out immediately following the events). This, along with other secondary sources (such as detailed crime figures), will allow us to examine the extent to which the spread of these riots was linked to a sense of shared identity with those who had rioted previously (that is, those who rioted 'saw themselves' in those who rioted before them, and those who lacked such a sense were less likely to riot). Third, we will use our findings to generate a wider debate about the nature of psychological transmission and the practicalities of addressing them. Activities will include workshops which will bring together researchers, practitioners (e.g., the police) and policy-makers in local and national government to address how we can mitigate against the spread of riots and violence.

Participants (N = 272) were recruited though Prolific, an online platform that connects researchers to participants around the world, and invited to take part in a study on how people experience and express emotions. This experiment was a 2x2 design in which male and female participants began by answering questions in part 1 of a 2-part questionnaire, hosted on Qualtrics, which was designed to make the participant’s gender salient. They then watched a 2 min 7 s video of either a male or female actor yawning during which they were filmed using their computer’s webcam. These video recordings were captured and held by a Canadian company, Nimbb. They were then redirected to complete the second part of the questionnaire which included questions about the degree to which they identified with the actor in the video, the behaviour and emotions of the actor, their tendency to experience emotional contagion measured using the Emotional Contagion Scale (Doherty, 1997) and self-reported urges to yawn. The participant videos were coded by a research assistant blind to the purpose of the study and condition, and a second naïve research assistant coded 10% of the videos.