American sociologist George Homans presented, in the article "Social Behavior as Exchange" (1958) and the book Social Behavior (1961), the theoretical approach he called the social exchange theory. New theoretical approach is guided by deductive logic. The social exchange theory derives from the critique that Homans developed toward the then-most dominant theoretical direction in America - functionalism. The theory of social exchange is based on several basic principles: the emphasis is on explaining the nature of relationships, rather than simply categorizing them; derivation of lower-ranking hypotheses must be obtained by deductive logic from abstract axioms of a higher level of generality; and the use of the principles of behavioral psychology as a general axiom.

Advocating the view that psychological, and not social principles, are the ones that should represent the axioms that should serve as the basis for crating hypotheses about the nature of social interaction and social institutions, led Homans to methodological individualism. He argued that it is impossible to understand social facts by using other social facts, but only through individual behavior. Social phenomena are always the result of the aggregation of individual behaviors. Since social phenomena arise and are maintained through individual behavior, the highest order principles in sociology must be those relating to individual behavior.

Homans' theory of social exchange views social behavior as "an exchange of activity, tangible or intangible, and more or less rewarding or costly, between at least two persons" (Homans, 1961, 13). The process of exchange is not reserved only for the economy but takes place in all aspects of social life because all interactions between individuals include seeking a reward and avoiding negative consequences. Rewards can be social or psychological, such as: recognition, support, status, satisfaction, etc. It is this desire for personal gain that drives the motivation for social exchange, not collective or symbolic forces. Homans mostly focuses on exchange interactions between two people or within small groups and does not deal with general forms of exchange, at a wider level of society.

Based on the exchange at the micro level, Homans explains more complicated phenomena such as: power, justice, and conformism. He wants to establish empirical hypotheses based on a small number of general principles, that are based on behavioral psychology. He introduces the categories he used in the book Social Group - Activities, Interactions, Sentiments, and Norms - into a new theoretical framework and combines them with the concepts of behavioral psychology. People in social exchange interactions tend to benefit and avoid harm, but they also have certain expectations about the consequences of exchange, so if their expectations are met, they feel satisfaction, and if they are not, they feel dissatisfaction and anger. Homans, on the other hand, recognizes that sometimes people do not make decisions, and often do not make long-term rational calculations, which would maximize their success in interactions.

Homans introduces six propositions (hypotheses) that could be used as axioms in sociological theory: 1) Success Proposition - people tend to perform those activities that have more often brought them greater rewards in the past; 2) Stimulus Proposition - people will more often repeat those actions that were rewarded in the past in the presence of a stimulus that in the past was associated with the reward; 3) Value Proposition - people will more often perform those activities that bring more valuable rewards; 4) Deprivation-Satiation Proposition - the more often a reward is received in recent past, the more its value decreases; 5) Aggression-Approval Proposition - rewards that are greater than expected and punishments that are less than expected, produce satisfaction and encourage the activities from which they arose; 6) Rationality Proposition - the choice between alternative activities is decided by the relative value of the consequences of the action, multiplied by the chance that the consequence (reward) will be realized. Homans further uses these assumptions to explain the most important group processes: power, authority, cooperation, competition, status, justice, leadership, conformism, and the processes that take place in institutions. More complex forms of social organization (macrostructure) are also built through these basic exchange processes.

                                           Peter Blau

American sociologist Peter Blau contributed to Social exchange theory, especially in the book Exchange and Power in Social Life (1964). Blau's approach to social exchange theory is based on the study of interpersonal interaction in small groups. He believes that there are four basic processes of exchange: attraction, competition, differentiation, and integration, each of which takes place, both between individuals and between collectives. These processes of exchange, when they take place in personal interaction, are guided by the rewards that individuals receive from that interaction. Rewards can be tangible or intangible (emotional). The social structure grows out of the established relations of exchange within the group. The individual search for awards leads to differentiation, but also cohesion in the group. Individuals who have a greater ability to give rewards to others grow into group leaders. Because it is impossible to achieve direct exchange, at the level of global society, between all individuals, at the macro level common values ​​and norms are supported by the indirect social exchange. Values ​​and norms, adopted as a consensus, govern the processes of social integration and differentiation at the level of complex social structures.

                           Richard Emerson and Karen Cook

American sociologist Richard Emerson used his study of power relations in society to further develop social exchange theory. Emerson sought to challenge the dominant view of power in the social sciences, the view that power is possessed by individuals and institutions that control the most important resources. He believed that power lies in the very relationship between individuals and institutions, therefore, that power is a relational phenomenon. The power of one person over another person is commensurate with the level to which the other person depends on the resources that the first person possesses. To define such a view of power, Emerson introduces the notion of "power-dependence relations." Such power relations are always manifested within the network of human relations. Using the concept of power-dependence relations, and within the theoretical framework of the social exchange theory, Emerson studied the issues of coalition building, social cohesion, commitment, trust, and solidarity. 

Emerson and Karen Cook researched how network structure affects the dependence, power, and commitment of network members. In Cooperation Without Trust (2005), Cook discusses how trust between actors affects the "power-dependence relations" (Emerson) that exist between them. She believes that the relations of social exchange (in marriage, at work, or in friendly relations) contain mutual dependence, which can be defined as a relationship of "encapsulated interest". The notion of encapsulated interests refers to the trust that one actor (individual or collective) places in another actor because he (or she or they) believes that the other actor accepts the interests of the first actor and unites those interests with his own interests. Cook believes that if there is unequal power in a relationship, it is difficult to develop trust because the relative power of the actors will affect the way they experience the relationship. This theoretical approach to the relationship of power and trust can be applied to individuals, as well as to relations between organizations or between states.

References:

Blau, Peter. Exchange and Power in Social Life (1964);                                                                                        Cook, Karen S., and Richard M. Emerson. “Power, Equity and Commitment in Exchange Networks”, in American
Sociological Review (1978); 
Cook, Karen S., Richard M. Emerson, Mary R. Gillmore, and Toshio Yamagishi. “The Distribution of Power in
Exchange Networks: Theory and Experimental Results”, in American Journal of Sociology (1983);
Cook, Karen S., and Toshio Yamagishi. “Power in Exchange Networks: A Power-Dependence Formulation”, in  Social Networks (1992);

Cook, Karen S. „Advances in the Microfoundations of Sociology: Recent Developments and New Challenges for Social Psychology”, u Contemporary Sociology (2000);

     -     Social Capital: Theory and Research (2001);

     -     Trust in Society (2001);

     -     Trust and Distrust in Organizations: Emerging Perspectives (2004);

     -     Cooperation Without Trust (2005);

„Exchange Theory: Part I: A Psychological Basis for Social Exchange”, and „Exchange Theory: Part II: Exchange Relations and Networks”, in Sociological Theories in Progress Joseph Berger (ed.) (1972);

Homan, George. „Social Behavior as Exchange”, in American Journal of Sociology (1958);

     -     Social Behavior: Its Elementary Forms (1961).