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.