Abstract
As Kahneman and Tversky pointed out, gains and losses are relative: the amount of reward earned on the previous task affects perception of current task earnings. Too often psychological studies only compare high- and low-reward conditions without considering reward history. We examined participant responses to trial-by-trial reward variations within the priming of pop-out paradigm, where people detect targets faster following trials with the same-colored targets over trials with different-colored targets (Maljkovic & Nakayama, 1994; 2000). Participants were cued with expected reward magnitude starting 400 ms prior to trial onset. Independent of reward history, we confirmed that high-reward trials produced faster search times than low-reward trials. When reward history is considered, we observed that there was facilitation only when rewards increased from the previous trial. Interestingly, the facilitation occurred for targets that were colored differently from the previous trial, but not for targets that were colored the same, resulting in a net reduction in the priming of pop-out effect. Thus, in addition to absolute effects of reward, relative increases in reward from one trial to the next influence search performance. The effects of these relative variations in gains and losses over time merit further study.
This work is supported by NIH EY014193.