Abstract
Perceptual learning shows that our perceptual ability can improve, and numerous previous studies have focused on increasing sensitivity to trained stimuli. However, another way of improving perceptual ability is to see stimuli more accurately, especially when one misperceives a given stimulus through optical illusion. The current study investigated whether the illusion can be reduced through perceptual learning, employing the tilt illusion in which the orientation of the center grating is misperceived because of the surrounding grating’s orientation. The study consisted of seven sessions: a pretest, five sessions of training, and a posttest. In pretest and posttest trials, participants were given a training stimulus, consisting of a center grating with (tilt-illusion condition) or without the surrounding grating (center-grating-only condition). The orientation of the center grating was one out of 357°, 0°, 3°, 87°, 90°, and 93°, and the orientation of the surrounding grating was 72° or 162°. Participants were asked to rotate the center grating by pressing arrow keys on a keyboard until they perceived it vertically or horizontally, and the amount of illusion was defined as the difference between the actual and the perceived orientation. Each training session comprised 450 trials. Participants were randomly assigned to the control training group, which were given only a center grating as a training stimulus, or the illusion training group, which were given both a center and a surrounding grating. During training sessions, response feedback was provided. Consequently, a smaller amount of tilt illusion was found after training sessions. In particular, the learning effect was larger in the illusion training group than in the control training group. These results suggest that learning occurs in such a way as to suppress the effects of surrounding stimuli.
Acknowledgement: 2017S1A5A8021943(National Research Foundation of Korea)