The Evolution of Cooperation* *
Robert Axelrod
Professor of Political Science and Public Policy, University of Michigan, Ann Arbor. Dr. Axelrod is a member of the American National Academy of Sciences and the American Academy of Arts and Sciences. His honors include a MacArthur Foundation Fellowship for the period 1987 through 1992.

Under what conditions will cooperation emerge in a world of egoists without central authority? This question has intrigued people for a long time. We all know that people are not angels, and that they tend to look after themselves and their own first. Yet we also know that cooperation does occur and that our civilization is based upon it. A good example of the fundamental problem of cooperation is the case where two industrial nations have erected trade barriers to each other’s exports. Because of the mutual advantages of free trade, both countries would be better off if these barriers were eliminated. But if either country were to eliminate its barriers unilaterally, it would find itself facing terms of trade that hurt its own economy. In fact, whatever one country does, the other country is better off retaining its own trade barriers. Therefore, the problem is that each country has an incentive to retain trade barriers, leading to a worse outcome than would have been possible had both countries cooperated with each other.
*

Adapted from Robert Axelrod, The Evolution of Cooperation. New York: Basic Books, 1984. Reprinted by permission.

1

2 / Process of Change

The Computer Tournament This basic problem occurs when the pursuit of self-interest by each leads to a poor outcome for all. To understand the vast array of specific situations like this, we need a way to represent what is common to them without becoming bogged down in the details unique to each. Fortunately, there is such representation available: the famous Prisoner’s Dilemma game, invented about 1950 by two Rand Corporation scientists. In this game there are