In 2017, psychologist Koske Takahashi from Chuke University (Japan) developed an optical illusion that illustrates the concept of curvature blindness. And at the same time it serves to identify it in people - over the past time it turned out that this is a massive effect. Recently, a scientist tweaked the illusion based on new knowledge about how the brain works to make it as convincing as possible.
The essence of the illusion is that the geometric shape of all the lines in the figure is the same, but our brain sees one half of them as smooth waves, and the other half as broken curves. This is not a problem with the eyes; upon closer examination, it is clearly seen that the curvature and angles of the lines are the same. It is the brain that makes the mistake, and in those cases when the most accurate assessment is needed. A contrasting image, on a bright or dark background, we see without error, but on a gray background, the same "curvature blindness" is activated.
Takahashi, as he studied the phenomenon, came to the conclusion that this is a side effect of human adaptation to the conditions of civilization. In the wild, clear geometric shapes are extremely rare, but among artificial things, in the human world, they prevail. In the human brain, the mechanisms for recognizing angles and curves compete with each other, and the former began to dominate the latter. This helps, for example, to quickly find an instrument in the grass or to notice a structure, a sign, a floating object among the waves from afar.
To test the hypothesis, improvements were made to the original illusion - the lines from monophonic steel became variegated, now they alternate between dark and light areas. But in one case, the sides of the wave are painted in different colors, they join at the top and this difference looks like an angle with clear straight lines. On the contrary, in another case, the upper and lower parts of the wave are painted in different colors, this hides the bend, visually adds smoothness to it. The brain is deceived very easily, the person seems to be partially blind, and does not notice the obvious things.