Most human relationships are characterized by reciprocal patterns of give-and-take that can be studied using a decision-making task called the Centipede game. The game involves 2 players alternating in choosing between cooperation and defection, with their choices affecting payoffs to themselves and the co-player. We compared trust and cooperation of Japanese and U.K. samples in the Centipede game. To increase the game’s applicability to real-life decision situations, we added 3 treatment conditions to manipulate payoff information. Our between-subjects design comprised the following 4 conditions: (a) full payoff information, (b) full payoff information framed as percentages, (c) partial payoff information with absolute (own payoff) information only, and (d) partial payoff information with relative information only. Comparing Japanese and U.K. students’ decisions, the Japanese cooperated significantly more frequently than the British. The manipulation of payoff information also affected decision making. In Japan, both treatment conditions with incomplete information yielded significantly higher cooperation levels than the control. In the U.K., only the condition with absolute payoff information produced significantly higher cooperativeness. Overall, these findings suggest that Japanese samples cooperate more frequently in repeated interactions than British samples and that this may be due to the assurance-based trust elicited by reciprocal relationships that has been identified as a typical feature of Japanese culture. In situations with incomplete information, expectations about the stake size may guide decision making, with lower expectations resulting in higher cooperation levels.