Social identity refers to the part of an individual's self-concept that is derived from their membership in various social groups, such as their nationality, ethnicity, gender, religion, or occupation.

Social Identity Theory, proposed by Henri Tajfel and John Turner, explains how individuals' self-concept is influenced by their membership in social groups. It suggests that individuals derive a sense of identity and self-worth from their group memberships and strive to maintain a positive social identity.

Social categorization is the process by which individuals mentally group themselves and others into social categories based on shared characteristics, such as race, gender, nationality, or occupation. This process helps individuals simplify and organize their social world.

Social identity influences individuals' behavior in various ways, including motivating them to conform to group norms, leading them to favor members of their own group over members of other groups, and increasing their self-esteem and sense of belonging.

In-group favoritism is the tendency for individuals to favor members of their own group over members of other groups. This bias can manifest in various forms, such as giving preferential treatment to in-group members, evaluating them more positively, and cooperating with them more readily.

Social identity maintenance refers to the process by which individuals strive to maintain a positive social identity by conforming to group norms and expectations. This can involve adopting the group's values, beliefs, and behaviors, as well as avoiding behaviors that might threaten the group's reputation.

Groupthink is a phenomenon that occurs when group members suppress their individual opinions and conform to the majority view, even if they disagree with it. This can lead to poor decision-making and a lack of critical thinking within the group.

Social Comparison Theory, proposed by Leon Festinger, explains how individuals compare themselves to others in order to evaluate their own abilities and worth. This theory suggests that individuals are motivated to maintain a positive self-concept and will engage in social comparison to assess their standing relative to others.

Lateral social comparison is the tendency to compare oneself to others who are similar to oneself in terms of social status, abilities, or other relevant characteristics.

Cognitive dissonance is the phenomenon that occurs when individuals strive to reduce the inconsistency between their beliefs and behaviors. This can involve changing their beliefs, changing their behaviors, or finding ways to rationalize the inconsistency.

Attribution theory, proposed by Harold Kelley, explains how individuals attribute causes to their own behavior and the behavior of others. This theory suggests that individuals use various types of information, such as the consistency, distinctiveness, and consensus of behavior, to make attributions about the causes of behavior.

Self-serving bias is the tendency for individuals to attribute their successes to internal factors, such as their own abilities and efforts, and their failures to external factors, such as bad luck or difficult circumstances.

Actor-observer bias is the tendency for individuals to attribute the behavior of others to internal factors, such as their personality or intentions, while attributing their own behavior to external factors, such as the situation or circumstances.

Confirmation bias is the phenomenon that occurs when individuals seek out information that confirms their existing beliefs and ignore information that contradicts them. This bias can lead to distorted perceptions of reality and make it difficult for individuals to change their minds.

Self-perception theory, proposed by Daryl Bem, explains how individuals form beliefs about themselves based on their own behavior. This theory suggests that individuals observe their own behavior and infer their attitudes and beliefs from their actions.