Reward produces learning of a consciously inaccessible feature

Reward has significant impacts on behavior and perception. Most past work in associative reward learning has used distinct visual cues to associate with different reward values. Thus, it remains unknown to what extent the learned associations depend on the consciousness. Here we resolved this issue by using an inter-ocular suppression paradigm with the monetary rewarding and non-rewarding cues identical to each other except for the eye-of-origin. Thus, the reward coding system cannot rely on the consciousness to select the reward-associated cue. Surprisingly, the targets in the rewarded eye broke into awareness faster than those in the non-rewarded eye. We further revealed that producing this effect required both attention and inter-ocular suppression. These findings suggest that the humans reward coding system can produce two different types of reward-based learning. One is independent of the consciousness yet fairly consuming attentional resource. The other one results from volitional selections guided by top-down attention.