Kurt Lewin, the 20th century German-American psychologist, is recognized as the founder of social psychology - the study of how the personality, attitudes, motivations, and behavior of the individual influences and is influenced by the group.
Lewin studied group dynamics and organizational development and challenged the prevailing "nature vs nurture" debate on behavior. Departing from conventional psychological theory, he developed a mathematical equation of behavior which claimed that an individual's immediate situation - not necessarily past influences - was a strong determinant of behavior.