Concerned with how a person"s behavior, thoughts, and feelings are influenced by the actual, imagined, or implied presence of others. Performance is affected by presence of other people: meta- analysis of 200 studies and 20 000 subjects, simple tasks are enhanced by presence of others, complex tasks are impaired by presence of others. People do not work as hard in groups as they do alone. Possible explanations: indirect link between effort and outcome: diffusion of responsibility, kitty genovese. People have a natural tendency to evaluate their opinions and abilities. If non- social information is unavailable (gpa), we evaluate abilities by comparing to other people. People prefer to compare themselves to others that are close to them. Conformity- changing ones behavior to match others: asch"s classic study, 6/7 people say wrong answer and other does too, causes of conformity, normative social influence- desire to gain approval/avoid rejection. Informational social influence- group may provide valuable information.