New Master Thesis Assignments

The effects of bystanders on perpetrators


A key theory in criminology which describes criminal behavior, namely Routine Activity Theory (RAT; Cohen & Felson, 1979) holds bystanders, or “guardians” as one of the three main proponents. The theory holds that for crime to take place, three elements need to converge: For crime to occur it is necessary that there is (1) a motivated offender, (2) a suitable target, (3) the absence of a capable guardian. This guardian can be anyone who is nearby and capable of stopping the crime. The informal guardian or passerby is the foremost important actor to prevent the crime from happening or escalating, because formal guardians are often much fewer in number.

At least in theory, the mere presence of a guardian can already prevent a crime from taking place. If the presence of others prevents a motivated offender, this is called preventive guardianship. However, sometimes even though there is a guardian, crimes still take place. In that case the “repressive guardian” or active bystander can be the first to respond and stop the situation from escalating. However, social psychological research on the bystander effect --an effect that explains how people often fail to intervene during crimes or accidents especially when other bystanders are around-- and criminological research into repressive guardianship shows that people often fail to do so (Fischer et al., 2011)

In previous research the focus was mostly on why guardians or bystanders do not intervene. In the current research, the focus lies on the perpetrator. It is of yet not clear when and if perpetrators actually care about the presence of guardians or bystanders, and if it deters them from performing their transgressions. Moreover, how perpetrators interpret non-intervention by guardians and bystanders is central to this study. Does it make them more likely to repeat the transgression, and does it perhaps make them feel that the transgression is more acceptable when there were many bystanders who did not intervene?


First you will independently review social psychological literature on the bystander effect, some key articles about routine activity and offending. After this we will together design a (quasi)-experiment. One could think about a quasi-experiment in which we ask participants to play a game in which they need to perform a transgression, at a location where guardians are present, or not. Otherwise a computer task in the laboratory in which they need to cheat or commit fraud either in front of others, or alone. Or a vignette study in which they have to imagine performing a transgression.


  • Fischer, P., Krueger, J. I., Greitemeyer, T., Vogrincic, C., Kastenmüller, A., Frey, D., ... & Kainbacher, M. (2011). The bystander-effect: a meta-analytic review on bystander intervention in dangerous and non-dangerous emergencies. Psychological bulletin, 137(4), 517.
  • Latané, B., & Nida, S. (1981). Ten years of research on group size and helping. Psychological Bulletin, 89(2), 308.
  • Cohen, L. E., & Felson, M. (1979). Social change and crime rate trends: A routine activity approach. American sociological review, 588-608.


Interested in this assignment? Please contact coördinator Sven Zebel (