Overview: The initial decision maker in a "trust game" decides how much money to pass to the other person. All money passed is increased by a factor, M > 1, and the second mover then decides how much of this to return to the first mover and how much to keep. The Nash equilibrium for selfish preferences is to pass nothing, since a self-interested person would return nothing in the final stage. The game highlights issues of reciprocity and strategy, and the extent to which observed behavior is "rational" from a selfish, strategic perspective.

Money passed may be viewed as a risky investment that will pay off if the second mover reciprocates. Notions of trust and reciprocity should come up in class discussion. The seminal research paper in this area is Berg, Dickhaut, and McCabe (1995) "Trust, Reciprocity, and Social History," GEB.