The branch of human psychology that deals with the behavior of groups and the influence of social factors on the individual.social psychologist n. Branch of psychology concerned with the personality, attitudes, motivations, and behaviour of the individual or group in the context of social interaction. The field emerged in the U.S. in the 1920s. Topics include the attribution of social status based on perceptual cues, the influence of social factors (such as peers) on a person's attitudes and beliefs, the functioning of small groups and large organizations, and the dynamics of face-to-face interactions