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Bystander Project

About This Project

The aim of this project is to dramatically improve the quality of immersive social virtual environments (IVEs). By ‘quality’ we refer to the response of participants to virtual social situations, in particular the extent to which they respond realistically to what they perceive. By ‘response’ we mean at every measurable level, ranging from non-conscious physiological processes (such as changes in electrodermal activity or heart rate variability) through to overt behavioural, emotional and cognitive responses / including what they report in interviews about their subjective state of mind. By social IVEs we specifically refer to applications where one or more human participants interact with virtual humanoid characters (avatars) in a socially defined context. Specifically, our objectives are to improve the visual appearance of interactive characters and their interactive behaviour especially so that their behaviour responds appropriately to the behaviour of the participants. Third, social IVEs will be constructed that are well-studied in the social psychology literature, and which are of great societal importance, referred to as bystander behaviour in violent emergencies such as in street violence. Finally, these virtual social situations will be used in a series of experimental studies in order to test whether indeed these objectives do improve the quality of response of participants within these social IVEs.


One of our goals is to exploit our research in socially useful applications, and thereby also contribute to the growing body of research that uses VEs as a laboratory for social psychological research. In particular we consider the research program of Levine and colleagues at Lancaster on bystander behaviour in violent emergencies. This research program revisits the classic ‘bystander effect’ in social psychology. The bystander effect suggests that the more witnesses there are to an emergency, the less likely an individual bystander is to intervene. This phenomenon was identified as a consequence of the apparent inaction of 38 witnesses to the brutal rape and murder of Kitty Genovese in New York in 1964. The bystander effect is one of the most robust and reproduced effects in social psychology. However, it lacks practical utility, since for ethical and practical reasons it is not possible to study it scientifically under controlled conditions. In this project we aim to study the bystander effect in the context of virtual environments, where other work has shown that people do tend to respond realistically to virtual social situations.


Full Title: “Visual and Behavioural Fidelity of Virtual Humans with Applications to Bystander Intervention in Violent Emergencies” 

Press: Reuters coverage 2013,   BBC News 2010

Project Duration: 14/06/2008 to 30/06/2012
Project Findings

Under what conditions will a bystander intervene to try to stop a violent attack by one person on another? It is generally believed that the greater the size of the crowd of bystanders, the less the chance that any of them will intervene. A complementary model is that social identity is critical as an explanatory variable. For example, when the bystander shares common social identity with the victim the probability of intervention is enhanced, other things being equal. However, it is generally not possible to study such hypotheses experimentally for practical and ethical reasons. We showed that an experiment that depicts a violent incident at life-size in immersive virtual reality lends support to the social identity explanation. Male supporters of Arsenal Football Club in England were recruited for a two-factor between-groups experiment: the victim was either an Arsenal supporter or not (in-group/out-group), and looked towards the participant for help or not during the confrontation. The response variables were the numbers of verbal and physical interventions by the participant during the violent argument.


The number of physical interventions had a significantly greater mean in the in-group condition compared to the out-group. The more that participants perceived that the Victim was looking to them for help the greater the number of interventions in the in-group but not in the out-group. Verbal interventions made during their experience, and analysis of post-experiment interview data suggest that in-group members were more prone to confrontational intervention compared to the out-group who were more prone to make statements to try to diffuse the situation. In later experiments several factors where manipulated to vary the experimental results, including the size and social identity of a group of bystanders and improvements to the visual fidelity of the characters and the virtual environment.


The experimental platform which was developed serves as an enabling technology, providing researchers with a robust and ethical environment by which complex social and behavioural phenomena can be evaluated. We hope in the future to explore the influence of the bystander behaviour on the participant in order to discern which actions are more likely to diffuse a conflict situation similar to the one simulated above. This work would tackle several research challenges in the area of Computer Animation, such as the synthesis of believable responses of virtual characters and the seamless interaction of performing actors interacting with a real participant within a virtual environment.

Involved In This Project

Researchers Involved

Gavin Lewis -

Principle Funders

EPSRC (EP/F032420/1; EP/F030215/1; EP/F030355/1)

Institutions Involved

ICREA Spain / UCL - Prof. Mel Slater (PI)
Exeter Univerity - Prof. Mark Levine (PI)

Non-Academic Stakeholders

Ministry of Defence
Metropolitan Police
Jill Dando Institute

Slater M, Rovira A, Southern R, Swapp D, Zhang JJ, et al. (2013) Bystander Responses to a Violent Incident in an Immersive Virtual Environment. PLoS ONE 8(1): e52766. doi:10.1371/journal.pone.0052766

Richard Southern, Jian J. Zhang, Motion-Sensitive Anchor Identification of Least-Squares Meshes from Examples. IEEE Transactions on Visualization and Computer Graphics, vol. 17, no. 6, pp. 850-856, June 2011, doi:10.1109/TVCG.2010.95

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