Fig. 1.

Experimental design. On each trial, an initial cue indicated potential for reward followed by a variable delay period during which a white fixation cross was shown. Then a negative or neutral task-irrelevant picture (not shown here) was presented centrally and two bars were presented peripherally (not drawn to scale). The participant’s task was to indicate whether the bars are of same or different orientation while ignoring the central picture. Finally, each trial ended with a variable inter-trial interval. During the reward condition (left side), participants were rewarded if performance was both fast and accurate.