a??Reversals of fortunea?? in visual search: Fast modulatory effects of financial reward upon visual search performance

摘要

Rewards have long been known to modulate overt behavior. Less is known of their effect upon attentional and perceptual processes. Here we investigated whether the (changeable) monetary reward-level associated with two different a??pop-outa?? targets might affect color-singleton visual search and the phenomena of a??priming of pop-outa??, i.e. repetition priming for one target type versus the other. Our observers searched for a target diamond-shape with a singleton color among distractor diamond-shapes of another color (e.g. green among red, or vice-versa), then judged whether the target had a notch at top or bottom. Correct judgments led to monetary reward, with symbolic feedback indicating this immediately, while actual financial rewards accumulated for receipt at study end. One particular target color led to higher (10:1) reward for 75% of its correct judgments, while the other singleton target color (counterbalanced over participants) received the higher reward on only 25% of trials. These reward schedules led not only to faster performance overall for the more rewarding target color, but also increased trial-to-trial priming of pop-out for targets of that color. The actual level of reward received on the preceding trial affected this, as did (orthogonally) the likely level of reward. When reward schedules were reversed within blocks, without explicit instruction, a corresponding reversal of the effect upon search performance emerged significantly within around six trials, asymptoting at around fifteen trials, without observers' explicit knowledge of the contingency. These results establish that not only pop-out search but even priming of pop-out can be influenced by target reward levels, with search performance and priming effects dynamically tracking changes in reward contingencies.