Stimulus sequences preceding un-cued gaze shifts (one shift set).

<p>Stimuli were 1.8×2.8 cm (3.4×5.3 deg visual angle). Faces were not covered in the experiment. Two stimulus sequences were displayed simultaneously on a black background, separated horizontally by 4.2 cm (8.0 deg visual angle). Each sequence consisted of repeated presentations of five different stimuli in a random order. A homogeneous gray rectangle was displayed between successive stimuli for the same duration as the stimuli. The stimuli in the fixated sequence changed at 8 Hz, and the stimuli in the non-fixated sequence changed at 12 Hz (the rates for the left and right stimulus sequences switched when gaze shifted so the fixated sequence always changed at 8 Hz). Participants were instructed to look at the stimulus sequence on the starting side (left or right, counterbalanced across participants). At a time of their own choosing, they were to shift their gaze to look at the other, previously non-fixated, stimulus sequence. At each shift, the previously fixated stimulus sequence was replaced. They continued in this manner, alternating sides, for three sets of two shifts (one shift set is shown), after which there was a brief rest period during which recognition of the stimuli was tested. Each participant completed five blocks of three shift sets. Details for the stimuli and procedure are in the text.