Social psychology is the scientific study of how people's thoughts, feelings and behaviors are influenced by others. Attitudes are learned evaluations of people, objects or ideas that influence thoughts and actions. Attitudes have cognitive, affective and behavioral components and are formed through social learning, comparison, experiences and potentially genetics. Attitudes can change through persuasion using communicators, messages, audiences and channels of communication. Various scales have been developed to measure attitudes, including Likert scales, Thurstone scales and Bogardus social distance scales. Group dynamics, conformity, cohesiveness and leadership are also areas of study in social psychology.