Computer Simulation of Crowd Dynamics and Destructive Crowd Behavior

The social processes that lead to destructive behavior in celebratory crowds can be studied through an agent-based computer simulation. Riots are an increasingly common outcome of sports celebrations, and pose the potential for harm to participants, bystanders, property, and the reputation of the groups with whom participants are associated. Rioting cannot necessarily be attributed to the negative emotions of individuals, such as anger, rage, frustration and despair. For instance, the celebratory behavior (e.g., chanting, cheering, singing) during UConn’s “Spring Weekend” and after the 2004 NCAA Championships resulted in several small fires and overturned cars. Further, not every individual in the area of a riot engages in violence, and those who do, do not do so continuously. Instead, small groups carry out the majority of violent acts in relatively short-lived episodes. Agent-based computer simulations are an ideal method for modeling complex group-level social phenomena, such as celebratory gatherings and riots, which emerge from the interaction of relatively “simple” individuals. By making simple assumptions about individuals’ decision-making and behaviors and allowing actors to affect one another, behavioral patterns emerge that cannot be predicted by the characteristics of individuals. The computer simulation developed here models celebratory riot behavior by repeatedly evaluating a single algorithm for each individual, the inputs of which are affected by the characteristics of nearby actors. Specifically, the simulation assumes that (a) actors possess 1 of 5 distinct social identities (group memberships), (b) actors will congregate with actors who possess the same identity, (c) the degree of social cohesion generated in the social context determines the stability of relationships within groups, and (d) actors’ level of aggression is affected by the aggression of other group members. Not only does this simulation provide a systematic investigation of the effects of the initial distribution of aggression, social identification, and cohesiveness on riot outcomes, but also an analytic tool others may use to investigate, visualize and predict how various individual characteristics affect emergent crowd behavior.

History of Maltreatment and Psychiatric Impairment in Children in Outpatient Psychiatric Treatment

There is increasing evidence that childhood victimization and attachment disruptions impact a child’s development. In this study, children and adolescents from an outpatient psychiatric clinic were assessed, measuring history of trauma, history of out-of-home placement, initial diagnoses, and CBCL internalizing and externalizing problem scores. Multiple regression analyses showed that both violent abuse trauma (physical/sexual abuse) and victim trauma (physical abuse/sexual abuse/witnessing domestic violence/witnessing community violence) are prevalent among patients with externalizing severity problems; concluding that diagnosis alone may not account for a history of victimization, but externalizing problem severity does. Overall, the study is consistent with past literature that it is important to acknowledge a child’s history of maltreatment and out-of-home placement when understanding their psychiatric development and diagnosis.