If subliminal reward cues input into the strategic processes involved in resource recruitment, the effects of rewards on pupil dilation should occur when the task is demanding (here, recall of five digits), but not when the task is undemanding (recall of three digits), as undemanding tasks can be completed routinely and do not require many resources. It is important to note that this interactive effect of reward and demand on recruitment of resources is expected to occur regardless of whether the reward is processed consciously or nonconsciously.Their results:
Pupil-dilation data indicated that valuable (compared with nonvaluable) rewards led to recruitment of more resources, but only when obtaining the reward required considerable mental effort. This pattern was identical for supraliminal and subliminal reward cues. This indicates that awareness of a reward is not a necessary condition for strategic resource recruitment to take place. These findings are in line with recent research suggesting that the unconscious has flexible and adaptive capabilities (Hassin, Uleman, & Bargh, 2005; Wilson, 2002). More generally, whereas analyses of costs (required effort) and benefits (value of rewards) are usually thought to require consciousness, our findings suggest that such strategic processes can occur outside of awareness—and these processes show in the eyes.