We measure the game behavior and analytic reasoning skills of expert strategic reasoners: professional GO players. We argue for a distinction between what we call “strategic” and “analytic” reasoning skills and present separate measures to elicit strategic and analytic abilities. The paper investigates the behavior of our subject pool in many different types of one-shot games, including the Traveler’s Dilemma, Centipede, Kreps, and Matching Pennies games. We observe that increased strategic skill predicts a greater probability of Nash behavior, while greater analytic skill predicts more cooperative play, even when such behavior is inconsistent with individual rationality.