Conducted a naturalistic study on Halloween to assess the effects of 3 deindividuation variables (anonymity vs nonanonymity, alone vs group, and groups with or without a child who was made responsible for the group’s actions) on stealing by children. Concealed raters unobtrusively observed approximately 1,300 trick-or-treating children who were assigned to various conditions and given an opportunity to steal candy and money. Significantly more stealing was observed under conditions of anonymity and in the presence of a group. There was also an Anonymity-Group interaction. Altered responsibility affected the transgression rate only when both the leader and members were anonymous. The highest rates of stealing occurred among anonymous children in groups with altered responsibility.
Diener, E., Fraser, S. C., Beaman, A. L., & Kelem, R. T. (1976). Effects of deindividuation variables on stealing among Halloween trick-or-treaters. Journal of Personality and Social Psychology, 33(2), 178-183.
http://dx.doi.org/10.1037/0022-3514.33.2.178