Better late than never? The effect of feedback delay on ERP indices of reward processing.

The feedback negativity (FN), an early neural response that differentiates rewards from losses, appears to be generated in part by reward circuits in the brain. A prominent model of the FN suggests that it reflects learning processes by which environmental feedback shapes behavior. Although there is evidence that human behavior is more strongly influenced by rewards that quickly follow actions, in nonlaboratory settings, optimal behaviors are not always followed by immediate rewards. However, it is not clear how the introduction of a delay between response selection and feedback impacts the FN. Thus, the present study used a simple forced choice gambling task to elicit the FN, in which feedback about rewards and losses was presented after either 1 or 6 s. Results suggest that, at short delays (1 s), participants clearly differentiated losses from rewards, as evidenced in the magnitude of the FN. At long delays (6 s), on the other hand, the difference between losses and rewards was negligible. Results are discussed in terms of eligibility traces and the reinforcement learning model of the FN.