Psychological perspectives are critical for understanding the concept of security because they explain and predict processes that may promote violent conflict or peaceful relations between nations and other groups (Bar-Tal 2007; Carroll, Wichman, and Arkin 2006; Huddy, Feldman, and Weber 2007; Leidner, Tropp, and Lickel, 2013). Psychological approaches examine these processes on multiple levels, such as relations between ethnic or religious groups within a nation as well as relations between nations.

The factors that motivate people's behavior and decision making, whether in relations with other groups or in support of national policies, are far more complex than a rational calculation of costs and benefits. Psychology has specified a range of biases that influence human behavior and decision making, in particular with regard to the groups with which people identify and in which they categorize others (Tajfel et al. 1971; Tajfel and Turner 1986; Turner et al. 1987).

Psychological contributions to the study of security focus on structural and subjective factors that predict people's perceptions and feelings of insecurity, the consequences those feelings of insecurity have on their attitudes and behavior (Bar-Tal and Jacobson 1998; Huddy et al. 2007), as well as the factors that may be necessary to enhance their sense of security. An underlying premise is that insecurity – whether actual or perceived – is an undesirable psychological state. Correspondingly, the need for security motivates people to diminish this state, prompting attitudes, emotions, and behaviors that can promote or hinder positive relations between groups (Huddy et al. 2007; Skitka et al. 2006). For the purposes of this chapter, we use the term “groups” to refer to large collections of individuals who categorize themselves, or whom others categorize, on the basis of ethnicity, race, nationality, political orientation, religion, or other categories that society recognizes as constituting meaningful groups (see Roccas and Elster 2012). The psychological need for security may lead people to identify more strongly with certain groups (e.g., Hogg 2010) or to antagonize or avoid members of other groups, as contrasted to building positive relationships across group boundaries (e.g., Leidner et al. 2013; Pettigrew 1998).

The current chapter focuses on theory and research from social and political psychology, and in particular the processes that pertain to relations between groups.