Fig. 1.

Stimulus setup. (a) Four small dots are placed around one search item; the dots designate the target and serve to mask it. In 67% of the trials the dots remain on screen after the search items disappear from screen (TM trials). In the remaining trials, search items and the dots disappear simultaneously (NTM trials). The small arrow indicates that search items in the lower quadrant are displaced away from the horizontal meridian to avoid potentially ambiguous magnetic field configurations (see Experimental Procedures). (b) Summary of the target duration individually adjusted for each subject (staircase procedure).