Vol.8 The wonder of optical illusion

Optical illusions, also known as “visual illusions,” occur when objects are perceived to be different from what they actually are. There are various types of optical illusions, including those in which the size, angle, or color of an object appears to change; a stationary object appears to move; an object that is not there appears to be seen; and a flat object appears to be three-dimensional.

The act of seeing is the cooperative work of our eyes and brain. Although visual illusions are perceived by the eyes, most are believed to be caused by the brain. The scientific study of optical illusions began in the 19th century, but they were known to people much earlier. In the Parthenon in Athens, some columns are said to have been shaped to correct the illusion and make them appear more beautiful.

In this article, we will introduce two famous optical illusions.

Müller-Lyer illusion

Let us look at the horizontal lines of A and B. Comparing and contrasting the lengths of the two figures, does the horizontal line of B look longer than the horizontal line of A? The horizontal line of B appears to be longer than that of A. However, if we measure these lengths, we find that they are of the same length. This is a phenomenon called the “Müller-Lyer illusion,” which was announced more than 120 years ago.

Hermann grid illusion

Black squares are arranged on a white background, creating the appearance of gray circles between them. What is the difference between pictures A and B? In Picture B, there is a light gray circle between the corners of the adjacent squares, whereas in Picture A, there is no gray circle. However, do you still see them in A? This illusion is known as the “Hermann grid.

If you look at books and websites on visual illusions, you will see many impressive illusions. Why not experience the mysterious world of illusions yourself?
As optical illusions are psychological phenomena that vary from person to person, some people do not perceive them. Please do not worry if you do not experience an illusion.

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