Fig. 1.

Experimental design. a Spatial arrangement: 3 white luminous dots (angular size 0.2°) were presented on a black computer screen 57 cm from the subject, one at the center of the screen and the others at an eccentricity of ±10° horizontally or vertically. b, c Temporal arrangement. Each trial started by lighting one central dot during approximately 1,500–2,000 ms. For the gap task, between the fixation offset and the target onset, there was a gap of 200 ms (b); for the overlap task, the fixation stayed on 200 ms after the target onset (c). The target, one of the eccentric dots, appeared for 1,500 ms.