Figure 1.

Task structure. Each trial began with an auditory preparatory (Prep.) cue indicating which of two peripheral locations subjects should covertly attend. After a variable SOA, Gabor patches appeared briefly at both locations, coincident with an auditory cue indicating the target stimulus. Subjects reported the orientation of the Gabor at the target location with a button press. In some task blocks, targets were very low contrast and performance was limited by visibility. In other blocks, targets were high contrast and performance was limited by the small difference in orientation between target types.