Reward reveals dissociable aspects of sustained attention.

Although reward is known to have a powerful influence on performance, its effects on the ability to continuously sustain performance over time are poorly understood. The current study examines multiple measures of sustained attention (accuracy and variability) and their decrements over time, while introducing reward in the form of a monetary incentive or the promise of early completion. Compared with unrewarded participants, rewarded participants demonstrated greater overall accuracy and lower reaction time variability. However, rewarded and unrewarded participants displayed nearly identical decrements in performance over time, suggesting that these aspects of sustained attention are far less malleable by enhanced effort. This study helps to resolve conflicting models of sustained attention as it reveals that some aspects of performance are due to motivational lapses whereas others are due to the depletion of cognitive resources that cannot be easily overcome.