It is common practice for psychology researchers to recruit their sample of participants from the undergraduate student population. Participants are typically compensated with partial course credit or a monetary payment. The current study reveals that the motivation to participate in a study (cash versus course credit) can relate to performance on a behavioral task of rewarded memory. In Experiment 1, undergraduate participants were recruited and compensated for their time with either partial course credit or cash. Potential performance-based cash rewards were earned during a rewarded memory task, where correct recognition of half the stimuli was worth a high reward and the other half a low reward. Memory for high reward items was better than low reward items, but only for the cash group. The credit group did not modulate their performance based on the value of the stimuli. In Experiment 2, undergraduates were compensated with partial course credit for their time and given the opportunity to earn a bonus credit for performance on a memory test. The findings were in line with the results from the credit group of Experiment 1, suggesting that the modulation of performance in the cash group of Experiment 1 cannot be accounted for by congruency between motivation to participate and reward for task performance. Of methodological importance, the findings indicate that recruiting and compensating participants with cash versus course credit may influence the results on a rewarded memory task. This factor should be taken into consideration in studies of reward motivation.