Fig 2. Stimulus presentation protocol for three example trials of the pairwise psychophysical task.

A pair of element texture patterns was presented for 400 ms for each trial. Observers had unlimited time to choose the more regular-appearing pattern using a numeric keypad, followed by the next trial. A fixation target was shown throughout the experiment. Note that this schematic depiction is for demonstration purposes, and the actual size and scale of stimuli are as described in ‘Design and Procedure’.