Figure 1. Target perceptual features, session sequence, and perception matching paradigms.

(A) The target image and afterimage perceptual features were: (1) sharpness, (2) contrast, and (3) duration. (B) Participants completed four task phases in the following order: (1) image and (2) afterimage sharpness perception matching and (3) image and (4) afterimage contrast and duration perception matching. (C) The stimuli and controllable images presented in the perception matching tasks. The afterimage perception is depicted as a dashed outline because no image was physically presented – the afterimage is an illusory conscious perception. Depending on the task phase, the controllable image allowed participants to manually adjust its sharpness or contrast. The controllable image is depicted with a hand icon (not present during the task) to indicate that participants manually adjusted these images with key presses. (D) The main trial phases of the image perception matching task (Supplementary Movies 2 and 4). Each trial began with a fixation interval (6–8 seconds [s]). When the image stimulus appeared (4 s) on either the left or right side of the central fixation, participants were instructed to immediately adjust the controllable image using key presses to match with the image stimuli according to the target perceptual feature (i.e., sharpness and contrast/duration; see Image Sharpness and Contrast and Duration Perception Matching Paradigm Methods sections). A subsequent fixation interval (10–12 s) followed the Image & Report stage prior to initiating the next trial. (E) The main trial events of the afterimage perception matching task (Supplementary Movies 3 and 5). Each trial began with a jittered fixation interval (6–8 s). Next, the inducer stimulus was shown (4 s) on either the left or right side of the central fixation and, subsequently, an afterimage might appear. If an afterimage was perceived, participants were instructed to immediately adjust the controllable image to match with the target perceptual feature of their afterimage (i.e., sharpness and contrast/duration; see Afterimage Sharpness and Contrast and Duration Perception Matching Paradigm Methods sections). The Afterimage & Report stage completed when the participant no longer perceived their afterimage, and the remaining duration of time (10–12 s) was a fixation interval prior to initiating the next trial.