Figure 1.

Behavioral task.

Subjects completed a two-alternative forced choice task that required two judgments per trial: a perceptual response followed by an estimate of relative confidence in their decision. The perceptual response indicated whether the first or second temporal interval contained the higher contrast (pop-out) Gabor patch (highlighted here with a dashed circle which was not present in the actual display), which could appear at any one of 6 locations around a central fixation point. Pop-out Gabor contrast was continually adjusted using a staircase procedure to maintain ~71% performance. Confidence ratings were made using a 1-6 scale, with participants encouraged to use the whole scale from 1 = low relative confidence to 6 = high relative confidence.