When making judgments, individuals often utilize heuristics to interpret information. This paper reports on a series of experiments designed to test the ways in which incentive mechanisms influence the use of a particular heuristic in decision making. These experiments demonstrate how information regarding the number of available practice problems influences the behaviors of individuals preparing for an exam (the proportion heuristic). More importantly, the extent to which this information influences behavior depends critically on the way in which performance incentives are structured. In particular, relative compensation schemes magnify the influence of this heuristic, while joint compensation schemes dampen its influence. These results are discussed with respect to the literature on effective compensation.