Institutions are places where there are strict rules that give little choice to members of that institution. Examples include the armed forces, prisons, and mental institutions. Institutional aggression refers to aggressive behaviours adopted by members of an institution; for example prisoners may form gangs that commit violence against other inmates. Psychologists are interested in whether institutional aggression is caused by the personalities of the institution’s members (dispositional factors), or by the situation in which the members find themselves (situational factors).