Figure 1. Visual stimulation task presented during EEG recording and designed to elicit an SSVEP.

a) Participants viewed an alternating blue-yellow checkerboard pattern with positive and negative reversals across five different brightness intensities modulated with monotonically increasing lux. b) Checkerboards alternated at 25Hz and were presented for 20 seconds before an unpleasantness rating for each brightness intensity. Block order was randomized across participants. c) Participants’ unpleasantness ratings were measured using the Gracely Box Scale with textual descriptors.