Searching for the mechanisms of vision through the study of optical illusion: Vision as a device for observing brain activity itself

By Professor Hiroyuki Ito,
Faculty of Design and Research Center for Applied Perceptual Science

　This research project is my lifework as a member of the faculty. I study the characteristics of vision―chiefly, optical illusion―and how this relates to the mechanisms of vision in the brain, based on experimental psychology. I explain two examples here.

　Although many know about the complementary color afterimage, where we see the opposite of a color we have stared at, few are aware that shapes also change in the afterimage. Figure 1 is a phenomenon that I presented in the journal Psychological Science in 2012. We see polygons, such as hexagonal shapes, as afterimages after staring a circle in the peripheral optical visual field, whereas we see a circle as an afterimage after staring at a hexagon. This phenomenon indicates that in shape perception, curves and angled corners compete with each other for detection. Should you wish to confirm this phenomenon with your own eyes, please download the following PowerPoint file and try starting the slideshow.
(http://www.design.kyushu-u.ac.jp/~ito/shape-afterimage-E.pptx)

　An object that appears to be moving is not necessarily moving physically. Figure 2 is a phenomenon that I presented in the journal i-Perception in 2012; it is an optical illusion whereby a disk placed in the center of a radial pattern moves with the movement of the eyes, as shown in the left figure. If you slowly turn the object printed on the paper to the right and to the left―like steering a wheel with both hands―while staring at the center, it looks as though the disk is rotating in the opposite direction and trying to remain in the same position in space, as shown in the right figure. These phenomena are not fully explained, though it is thought that they are due to a malfunction in the detection of relative movement when the brightness of an object and its background are the same. If you also wish to confirm this phenomenon with your own eyes, please download the following PowerPoint file and try starting the slideshow.
(http://www.design.kyushu-u.ac.jp/~ito/pursuit-illusion-E.pptx)

　The leading character in the movie The Matrix learns that “the world that he lives is a virtual reality that was made by a computer” and wakes up to the real world. The world view of a vision researcher is similar to this. The world that we see is a “virtual reality” made in the brain, and what is sent from the eyes to the brain is not a picture of the outside world but a set of serial nerve impulses. Even “color” and “brightness” are “visualizations” of the information of nerve activities in the brain. The brain’s ability to render images of the world in real time is far superior to computers; thus, only optical illusions point out the contradictions of the “virtual reality” produced by the brain, and serve to awaken us to reality.
　The world that we see is an outcome of the activity of the brain, and optical illusion plainly reveals the character of this activity. Therefore, the study of optical illusion is linked to the study of the activity and mechanisms of the brain. Additionally, in terms of practical applications, it can be used in the prevention of accidents and in visual design by finding methods for avoiding optical illusions, or indeed by making use of the illusions. Optical illusions are also useful in entertainment media, and can be adopted in imagery for commercials, games, movies, and such. The optical illusions introduced here have been displayed at exhibitions such as the “Great Trick Art Exhibit” at Ehime Prefectural General Science Museum in 2015, and contribute to activities for science communication aimed at children.

Hiroyuki Ito（Faculty of Design）
email: ito (★)design.kyushu-u.ac.jp
URL: http://www.design.kyushu-u.ac.jp/~ito/

*Please replace the (★) in the e-mail address with @.