**2. Sociology and collective behavior**

Sociology deals with the study of human groups and the formation of institutions (dos Santos França, 2010; Merton, 1968). Its origin came from Comte, Spencer and other 19*th* century researchers' need for a distinct perspective of the human behavior that derived from the individualistic studies that had been performed previously. For instance, Comte stood out that the human mind could only develop in a social environment. Thus, following this premise, Psychology was not enough to study the human' social behavior (Turner & Killian, 1957).

At first, Sociology was focused on culturally-oriented groups or social groups which behavior follows established rules. Because of such interpretation, some spontaneous and unorthodox social actions were perceived as abnormal and unstable or as exceptions that did not draw further attention. Sociology, as a science, attempted to "frame" reality into well-defined and established patterns. If a certain social action could not fit into any of such patterns, the action was considered a mistake or even a wrongdoing until society accepts the new behavior and embraces it. Such acceptance could take decades or never happen.

Taking a whole new approach, the field of Collective Behavior deals with human groups and collectivities that contradict or reinterpret society's norms and standards. These collectivities' behavior is not entirely detached from the socially accepted behavior discussed earlier. However, collective behavior deals with social groups that deny or reinterpret society norms and standards. Ralph Turner and Lewis Killian at (Turner & Killian, 1957) defined collective behavior as "*the set of social behaviors which the usual conventions stop driving the actions and the individuals transcend, exceed or collectively subvert the standards and the institutionalized structures*" (dos Santos França et al., 2009). This definition implies that the individuals engaged in a collective behavior are no longer bound to the rules and norms of society and they are free to act the way they intended even if such behavior is not socially accepted. At first, their actions are related to the institutionalized and established actions found in Society. But, as soon their need for socially unaccepted actions is reached, they start to bend and to overrule the norms that were built by society, creating their own.

This sort of human group might happen due to many reasons, including by hazardous events, whether they are natural or human-induced. Also, their structure and formation follow a pattern that was mapped by some researchers. Finally, such mapped patterns could be used to understand disasters by a distinct perspective: how people react in a hazardous event and how this could be simulated in order to decrease material and human losses. The simulation model presented in Section 3 deeply applies the information described in this section.

### **2.1 Crowd simulation: Theoretical elements**

The understanding of the panic in crowds' phenomenon relies on the study of the collective behavior phenomenon. Thus, a historical overview is presented in the following sections, along with modern studies about panic and disasters, especially how people behave under such conditions. The following subsections show a historical overview of some studies of the collective behavior field and the theories that will be employed in Section 3 to build the simulation model.
