Cook, Karen

American social theorist and experimental social psychologist Karen S. Cook (b. 1946) has played a major role in advancing the theory and study of exchange and exchange networks and in developing and using rational choice theory more generally. Cook's substantive work can be grouped into these interconnected areas: exchange and power in exchange networks, distributive justice, generalized exchange, and, most recently, trust.

Educated at Stanford University, Cook first took a faculty position at the University of Washington, where she remained for two decades (she has been at Stanford University since 1998). There, she joined Richard Emerson in theoretical and experimental investigation of exchange networks. They focused on how network structure affects the dependence and thus power of network members, and on justice and commitment within networks.

This work led to the early and arguably most important finding in research on exchange in networks: that contrary to what had been thought previously, the most central actor in a network may not be the most powerful actor. Cook et al. (1983) predicted and then showed experimentally that in a five-actor line network (A-B-C-D-E, where each line indicates a possible exchange relation) in which each actor's partners are alternative sources of the same desired resource, most powerful will be the two actors adjacent to the end positions (B and D), not the most central actor (C), as previously thought. The theory follows from the power-dependence principle. End actors (A and E) are much weaker than their partners (B and D) because their partners have alternatives to the end actors as sources for the desired resource whereas the end actors have no alternatives to their partners. The central actor (C) is weaker than its partners (B and D) because in order to obtain anything, it must outbid the end actors (A or E), which again are weak and so inclined to be generous. The same power-dependence logic can be and has been applied to exchange networks of various sizes and configurations.

Following Emerson's death in 1982, Cook continued work on exchange in networks with others, in particular their former student Toshio Yamagishi. They looked first at positively connected networks, in which partners of a given network member are complementary, not competing. They reasoned and then showed that in such networks, the central member is the most powerful.

Cook's next step was away from processes in which actors are seeking only to maximize profit. From her earliest work on social exchange, Cook had been interested in justice and equity concerns, which can arise easily in exchange situations and temper the drive to maximize immediate profit. It was logical therefore to look at generalized exchange, an umbrella name for exchange processes that are not directed at maximizing short-term gain. Here, she was in the vanguard of a general move in the social sciences toward a more nuanced view of actors in exchange processes.

Specifically, generalized exchange refers to exchange processes in which an actor gives and is given to in return but what the actor receives is not contingent on what the actor gives. For example, in work published in 1993, Yamagishi and Cook investigated situations in which giving is in a chain, such that A gives to B, B gives to C, and so forth, until some actor gives to A. In addition, they have looked at situations in which group members can provide individually a good that benefits all group members, and at situations in which group members collectively provide a good for one group member at a time. This work contributes to the burgeoning theoretical and experimental literature on social dilemmas: situations in which individual actors are better off if they do not cooperate but if there is not enough cooperation by individual actors, then everyone in the group is worse off. In their research, Yamagishi and Cook showed how the structure of the exchange situation can affect cooperation and the collective outcome.

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