Have you ever heard of the effect of McCall? This is a strange feature of our brain – looking at the lines of different colors that alternate, people begin to see some shade of a completely different color. In 1965, the illusion was discovered and investigated by psychologist Celeste McCall.
The psychologist discovered, when a long time to look at black and white images, a person begins to see colors. The most noticeable effect can be achieved by using squares of vertical and horizontal lines. A tilt of the head by 90 degrees can strengthen or weaken this result. In fact, if you rotate images and look at them again, you can see that the shade has changed. And the longer you look at the original images, the longer this effect will last.
For the experiments of Celeste in 1975, 5 groups of 16 people were selected. They looked at the colored squares for 15 minutes. In one of the groups, the perception of colors remained all the same distorted after five days. Three months later representatives of the other four groups saw black and white squares as colored, though less bright. To stop this effect you need to look at squares of the same colors, but rotated by 90 degrees.