Experimental paradigm for the ‘explicit’ task. The explicit task included training and 1 block, consisting of 70 trials. Two sample trials (A and B) are displayed. At trial onset, two side-by-side images appeared (this default screen remained for the 5000 msec duration unless subjects executed a response). Continuous button pressing enlarged the corresponding image, as shown in both examples (A: right picture; B: left picture, both indicated by red box), for the 5000 msec trial duration; no response (for 500 msec) after initial response returned the side-by-side display. Each trial onset was preceded by a 1500 msec fixation cross to separate trials (not depicted in figure).