 From the book "The Psychology of Interpersonal Relations" (1958), Fritz Heider tried to explore the nature of interpersonal relationship, and espoused the concept of what he called "common sense" or "naïve psychology".In his theory, he believed that people observe, analyze, and explain behaviors with explanations.Although people have different kinds of explanations for the events of human behaviors, Heider found it is very useful to group explanation into two categories; Internal (personal) and external (situational) attributions.