Prior theorizing of rationality in social dilemmas suggests that individuals pursuing different interaction goals may 'perceive' different associations between competence and behaviour in a social dilemma, arguing that competitive individuals associate competence with noncooperation (i.e. noncooperation = smart), whereas prosocial individuals associate competence with cooperation (i.e. cooperation = smart; goal-prescribes-rationality principle, Van Lange Kuhlman, 1994). The present research examines whether cooperative interaction can be affected by subtle activation (or priming) of competence, and whether the effects may differ for competitive versus prosocial participants. Consistent with hypotheses, two experiments revealed that priming competence yielded reduced levels of cooperation (and greater exploitation) among competitors, and yielded no effects (Experiment 1) or a tendency towards enhanced cooperation (Experiment 2) among prosocials. The discussion considers theoretical implications of relatively subtle influences on cooperative interaction in social dilemmas. Copyright © 2004 John Wiley & Sons, Ltd.