Group think and Compliance

Group think is a type of thinking that occurs when people place more importance on maintaining group cohesiveness than on assessing the facts of the problem with which the group is concerned. This involves different types of group behaviors under this umbrella. For example, group polarization is the strengthening of shared beliefs. People who discuss shared views will come to believe in them more strongly-this can be positive or negative (ex. if the beliefs involve violence)
Groups tend to do things that individuals wouldn't usually do. Other types of group behavior include deindividualization or a lack of individual responsibility that comes from being in a crowd. This is sometimes referred to as Mob Mentality.

Compliance is the changing of ones behavior as a result of other people directing or asking for the change. There are ways to gain compliance like the “in the door technique.” This is the act of asking for a small commitment and, after gaining compliance, asking for a bigger commitment. People are more likely to say yes to something bigger if you say yes to something small first.