Stimulus–response learning and expected reward value enhance stimulus cognitive processing: An ERP study

Reward affects our attention to stimuli, prioritizing those that lead to high‐value outcomes. Recently, it has been suggested that such reward‐related cognitive prioritization might be associated with the process of learning new stimulus–response (S‐R) associations, because both are acquired through extended reward training, and once established, they are hard to overcome. We used event‐related potentials (ERP) to analyze the contribution of S‐R links to the formation of reward‐related cognitive prioritization during reinforcement learning. Reward‐related cognitive prioritization was measured by comparing the ERP signals for stimuli predicting high‐value and low‐value outcomes. In addition, we compared a strong S‐R link (same stimulus, same response), with a weak S‐R link condition (same stimulus, two different responses). The participants’ performance was more accurate and faster when the procedure allowed for establishing strong S‐R links and for high‐value outcomes. Furthermore, those stimuli associated with strong S‐R links showed a larger P3 amplitude at parietal sites. Value effects (larger ERP activity for those stimuli predicting a high‐value outcome) were obtained at parietal and occipital sites in the P3 time window. However, value effects did not benefit from strong S‐R links in either the P1 or the P3 components. These results suggest that strong S‐R learning is not necessary to develop reward‐related modulations of ERP activity. Attentional biases toward reward‐related stimuli show habit‐like properties. We tested the “attention habit” hypothesis using a new approach. Habits are sustained by stimulus–response (S‐R) associations. We compared reward‐related attentional bias in stimuli associated with a specific response (strong S‐R), with those associated with two alternative responses (weak S‐R). We found that reward and S‐R learning modulate our attention through independent processes. We conclude that S‐R learning is unnecessary to develop reward‐related modulations of attention.