Fig. 6.

Stimuli used in experiment 2. In experiment 2 the observer chose between masked and unmasked stimuli that differed in eccentricity. The underlying psychophysical task used Landolt's C stimuli is that the gap in the circle could be facing either up or down. Because stimuli were displayed at a random eccentricity, they were preceded by a cue that indicated the location the stimulus would appear in. The stimulus was flashed briefly immediately after the cue. In the masked condition, the stimulus was followed directly by a noise mask. In the unmasked condition, a blank interval (called the interstimulus interval, ISI), was inserted between the stimulus and the mask.