This project develops and experimentally and econometrically tests a theory of human behavior and learning in games. Under their previous NSF grant the investigators found evidence that human players can be characterized as having one of five models of other players. The proposed research will explore the robustness of these findings, and compare the current theory with alternatives. The investigators also found evidence for `rule learning` in a guessing game, and propose exploring the applicability of such a model to typical normal-form games. Consequently, this project contributes to a descriptive and prescriptive theory of games.