This study investigated the degree to which social identity influenced the transmission of behaviour, specifically yawning behaviour. This was an online experimental study that recruited participants (through Prolific) that had voted to Remain in the EU Referendum. Their identity as a Remain supporter was made salient before presenting them with a video of a group of actors yawning at intervals, or not yawning, and which indicated that the actors were either Remain supporters (ingroup) or Leave supporters (outgroup) or gave no indication of their identity. Participant's behaviour was recorded using their computer's webcam and later coded for various measures of yawning behaviour. The data has not yet been analysed although preliminary inspection shows that only 10 of 305 participants demonstrated yawning behaviour. This study used relatively naturalistic stimuli compared with previous studies on the contagious transmission of behaviour that used headless actors performing the target behaviour continuously and calls into question the conclusions drawn by studies using relatively unnatural stimuli.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.

Data collection method: UK participants were recruited though Prolific, an online platform that connects researchers to participants around the world, and invited to take part in a study concerning whether people differ in their processing of the emotions of others depending on whether those others do, or do not, share their political views. This experiment was a 3x2 design in which participants screened as ‘Remain’ voters in the EU Referendum began by answering questions in part 1 of a 2-part questionnaire, hosted on Qualtrics, which was designed to make the participant’s voting category membership salient. They then watched a 2 min video of a group of actors that were either scratching at intervals or sitting without scratching, with text added to video indicating that they were either ‘Remain’ supporters (ingroup), ‘Leave’ supporters (outgroup) or no text indicating their political orientation regarding Brexit. Thus, there were six conditions in all. Participants were randomly directed to each video condition by Qualtrics. Throughout the video, participants were recorded 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 actors in the video, the behaviour and emotions of the actors, the participant’s tendency to experience emotional contagion measured using the Emotional Contagion Scale (Doherty, 1997) and self-reported urges to yawn. The participant videos were coded for various yawning measures by a research assistant blind to the purpose of the study and condition, and a second naïve research assistant coded 10% of the videos to check for interobserver reliability. This experiment was preregistered prior to data collection. After exclusions due to failing the manipulation check or indication that the participant voted ‘Leave’ rather than ‘Remain’, N = 305.