created a number of theories explaining aspects of population structure that increased chances of intergroup relations. Blau viewed social structure as being somewhat stable, but he did identify two phenomena that he believed contributed to structural change within a population: social mobility and conflict. Blau thought social mobility, which he described as "any movement within a population by an individual," was beneficial to intergroup relations within a population structure, and theorized various scenarios involving social relations and mobility. Blau also theorized explanations for structural causes of conflict, focusing on population distribution as a cause of conflict separate from individual or political issues. According to Blau, structural conflict is linked to the inequality of status of groups, size of group, social mobility between groups, and the probability of social contact between groups. Blau determined that prevention of conflict within a population structure can be achieved through "multi-group affiliations and intersection in complex societies". Social exchange theory Social exchange provides an explanation of the interactions and relationships Blau observed while researching. He believed that social exchange could reflect behavior oriented to socially mediated goals. Peter started from the premise that social interaction has value to people, and he explored the forms and sources of this value in order to understand collective outcomes, such as the distribution of power in a society. People engage in social interactions in which we would not think deep about, but Blau suggested it is for the same reason why people engage in economic transactions. They need something from other people, the exchange. That then leads to an increase in social exchange in which people attempt to stay out of debt because it gives them an advantage, as well as potential power. Although social exchange can be genuine, when the goal for the individual to stay out of debt or to get something in return, it is selfishness. "The tendency to help others is frequently motivated by the expectation that doing so will bring social rewards" Blau explained that social exchange between individuals either stem from inherent rewards (things such as love or admiration) or external rewards (money, etc.). Blau expressed the difference between social exchange and the purchasing of goods, stating that there is an emotional component within social exchange that is nonexistent in everyday transactions. Blau also studied the social exchange that occurs within relationships. He believed that most thriving friendships occur when both participants are