Exchange Networks

An exchange network is a special case of a social network in which the nodes of the network are social actors (e.g., persons or groups) and the lines connecting the nodes are possible interactions between particular actors that may occur during the process of social exchange. Exchange networks may be complete, in which case they allow interactions between all pairs of actors, or incomplete, in which case they prohibit interactions between some pairs of actors. Hence, an exchange network is a structure of social constraints on the process of social exchange that unfolds [Page 265]among a group of actors. Research on social exchange networks has focused on the question of how variation in the structure of an exchange network affects the outcomes of the social exchange process that occurs among the actors in the network. This research has been pursued mainly with experiments, in which small groups of subjects have participated in a social exchange process that has been specified by the experimenter and that unfolds in a network structure that also has been specified by the experimenter.

The domain of possible exchange processes and structures that might be studied is large, because there are many forms of social exchange and varieties of structural constraint. In the experiments on exchange networks that have been conducted to date, much research has focused on one type of exchange network, referred to as a “negatively connected” exchange network, which is relatively simple to construct in laboratory settings. In rough outline, the experimental design for a negatively connected exchange network involves a small group of subjects who are assigned to particular positions in an exchange network; the exchange network constrains the pattern of interpersonal communication among the subjects (i.e., who can communicate with whom in the network), and the subjects are instructed to attempt to reach an agreement on the division of a pool of resources with one of the persons with whom they may directly communicate (i.e., an agreement on the fraction of the resources each actor will receive). There is a resource pool, usually of the same size, associated with each pair of persons who are in direct communication. The subjects are instructed that each subject may make at most one agreement with the other subjects, and they are promised a monetary reward according to the amount of resources they personally acquire from this agreement. Presumably, the subjects are motivated to reach agreements and maximize their payoffs. Depending on the structure of the exchange network, one or more agreements may be formed among the subjects, but no subject can be involved in more than one agreement. Indeed, some subjects may not be able to form an agreement, and if they do not, they receive no monetary payoff. An experimental trial with a particular group of subjects ends when no more agreements can be achieved in the group. Each group of subjects typically participates in numerous experimental trials, usually under the same structural conditions (same network, same position assignments, same rules of exchange), so that anything that happened on previous experimental trials may affect subjects' behavior on subsequent trials. Thus, the subjects may modify their behavior over the experimental trials in an effort to increase the amount of resources they acquire; for instance, subjects who were excluded from agreements on a trial might modify their behavior (offer a greater proportion of their available resource pools to other persons) on the next trial in order to increase the possibility of reaching an agreement with one of the persons with whom they are in communication.

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