In the field of psychology, social psychology is the scientific study of how the thoughts, feelings, and behaviors of individuals are influenced by the actual, imagined, and implied presence of others. In this definition, scientific refers to the empirical investigation using the scientific method, while the terms thoughts, feelings, and behaviors refer to the psychological variables that can be measured in humans. Moreover, the notion that the presence of others may be imagined or implied suggests that humans are malleable to social influences even when alone, such as when watching videos, quietly appreciating art, or even sitting on the toilet. In such situations, people can be influenced to follow internalized cultural norms. Social psychologists typically explain human behavior as a result of the relation between mental state and social situation, studying the factors/conditions under which certain behavior, actions, and feelings occur. Social psychology, thus, is concerned with the way these feelings, thoughts, beliefs, intentions, and goals, are cognitively constructed and how these mental representations, in turn, influence our interactions with others. Traditionally, the emergence of this discipline bridged the gap between psychology and sociology. During the years immediately following World War II, there was frequent collaboration 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 more macro features (e.g., social structure)—as the prefix of socio- denotes a societal influence—whereas psychologists may be more concerned with more micro features. Nevertheless, sociological approaches to psychology remain an important counterpart to psychological research in this area. In addition to the split between psychology and sociology, there has been a somewhat less pronounced difference in emphasis between American and European social psychologists, as, the former traditionally have focused more on the individual, whereas the latter have generally paid more attention to group-level phenomena.