Figure 1.

Schematic illustration of the experimental design. Subjects were presented with two squared apertures located in the left and right visual field. In the left aperture all dots moved either coherently upward (during even runs) or downward (during odd runs) and thus were perceived as a transparent surface. On some trials, this surface moved with a higher velocity, and subjects responded to those as targets. Within the right aperture all dots remained stationary during the intertrial interval (ISI) and during target trials, while on probe trials they performed a short coherent displacement into one of the eight cardinal or ordinal directions. While these movements could deviate from the motion direction of the attended surface by 0°, 45°, 90°, 135°, or 180°, they were completely irrelevant to the task and had to be ignored by the subjects.