Figure 1.

Stimulus and task for detection experiments: a, blank sectors; b, sectors with Gabor detection targets; c, subjects alternated their attention between left and right sectors. Blocks began with a 2 s delay to deploy attention upon the cued sector, and then subjects performed four 2.5 s trials. During each trial, there was a 50% probability that two threshold–contrast Gabors would be presented briefly at a random time and location within each sector. At the end of each trial, subjects pressed a button to indicate their yes/no detection judgment.