In public good situations, expectations concerning other persons' moves are important and subtle cues can affect these expectations. In Experiment 1, participants in a public good game who moved simultaneously made high contributions and expected their opponents to make high contributions. However, participants who moved pseudo-sequentially (one after the other, but without knowledge of the other's decision) expected their opponents to make medium-sized contributions, but made almost no contribution themselves. In Experiment 2, we manipulated expectations experimentally. Participants who moved simultaneously reciprocated what they expected their partners to do. Participants who moved pseudo-sequentially defected, regardless of what they expected from their opponents. Furthermore, we found that simultaneous movers were more likely than pseudo-sequential movers to conceptualize themselves and the other player as a group. This sense of groupness seemed to account partly for their inclination to reciprocate anticipated behavior.