Fig. 1.

(a) Top panel: example of the four neutral faces that were associated with different reward values (90% win, 60% win, 60% loss, 90% loss) during the conditioning phase. The first face corresponds to the High Reward condition, and the fourth face to the Low Reward condition. Bottom panel: example of two trials of the conditioning phase in which the participants had to predict whether the face down card would be of lower or higher value than the face up card. Following their key response, feedback was displayed. (b) Top panel: examples of the target clips (High Reward and Low Reward conditioned faces) and two of the oddball clips presented during the test phase. Bottom panel: example of two trials of the test phase. A fixation cross appeared during 1000 ms before the presentation of the 4000 ms clips of happy facial expressions made by the target or oddball faces. Participants had to make a keypress response every time an oddball clip was presented.