This project addresses how and why behavior in a resource dilemma differs when one only knows the choices of others versus only knows the state of the resource. Study 1 suggested that resource information is more valuable than social information, in that if the resource can be monitored, whether or not others’ choices can also be monitored has no impact on behavior. However, if the state of the resource is not known, the ability to know what others are doing is critical for cooperation. This seems to be because resource information encourages planning and long-term thinking, and social information encourages comparative thinking. Study 2 replicated the behavior pattern, revealed—surprisingly—that warnings that a resource is critically low undermine (rather than promote) cooperation, and that such responses depend on the availability of social and environmental information. Discussion focuses on how incomplete information about a resource might be addressed.