Social psychology is the scientific study of how thoughts, feelings, and behaviors are influenced by the real or imagined presence of other people or by social norms. Social psychologists typically explain human behavior as a result of the relationship between mental states and social situations, studying the social conditions under which thoughts, feelings, and behaviors occur, and how these variables influence social interactions. History Although issues in social psychology have been discussed in philosophy for much of human history, the scientific discipline of social psychology formally began in the late 19th to early 20th century. 19th century In the 19th century, social psychology began to emerge from the larger field of psychology. At the time, many psychologists were concerned with developing concrete explanations for the different aspects of human nature. They attempted to discover concrete cause-and-effect relationships that explained social interactions. In order to do so, they applied the scientific method to human behavior. The first published study in the field was Norman Triplett's 1898 experiment on the phenomenon of social facilitation. These psychological experiments later went on to form the foundation of much of 20th century social psychological findings. Early 20th century During World War II, social psychologists were mostly concerned with studies of persuasion and propaganda for the U.S. military (see also psychological warfare). Following the war, researchers became interested in a variety of social problems, including issues of gender and racial prejudice. During the years immediately following World War II, there were frequent collaborations between psychologists and sociologists. The two disciplines, however, have become increasingly specialized and isolated from each other in recent years, with sociologists generally focusing on high-level, large-scale examinations of society, and psychologists generally focusing on more small-scale studies of individual human behaviors. Late 20th century and modernity In the 1960s, there was growing interest in topics such as cognitive dissonance, bystander intervention, and aggression. In the 1970s, a number of conceptual challenges to social psychology emerged over issues such as ethical concerns about laboratory experimentation, whether attitudes could accurately predict behavior, and to what extent science could be done in a cultural context. It was also in this period where situationism—the theory that human behavior changes based on situational factors—emerged and challenged the relevance of self and personality in psychology. By the 1980s and 1990s, social psychology had developed a number of solutions to these issues with regard to theory and methodology. At