Schematic of the stimuli and protocol structure used in PSICAT. Stimuli are exemplified top left by a triangular Kanizsa subjective-contour-illusion target, displayed white-on-black; with the respective congruent red-line primer. Single trials of the protocol are shown in 2 × 2 conditions: congruent/incongruent × SCI/no-SCI. Congruent primer angles match the following target’s angles, incongruent do not match. Trials from each condition are distributed uniformly at random. Participant’s task is to classify whether targets are SCI or no-SCI; the primers are to be ignored. PSICAT consists of 550 trials in five blocks, and requires ~22 minutes to complete.