Another tricky optical effect

Another tricky optical effect

Have you ever heard of the McCall effect? This is a strange feature of our brain - looking at alternating lines of different colors, we begin to see some kind of completely different shade.

To start the effect, you need to look at the center of two color “exciting images” for a few minutes, constantly shifting your eyes between them. Best of all it works with red and green lines. Then, when looking at the vertical black and white lines, you can find that they have acquired a red, green or pinkish tint.

Tilting the head 90 degrees can enhance or reduce this effect. In fact, if you rotate the images and look at them again, you will notice that the hue has changed. And the longer you look at the original images, the longer this effect will last - hours, days, or even months in other cases.

But is this really the case, and why is this happening at all?

The effect is named after its discoverer, Celeste McColla Howard.She was the first person to discover the so-called “extra aftereffect,” which is an illusion that affects our brain for a long period of time.

Over the years, a series of studies of this effect has been carried out. In 1975, two researchers tested five groups of people of sixteen people, and, surprisingly, in one group, the effect did not show up after five days of research. In the other four groups, it manifested itself by half to the record in 2040 hours - or almost three months.

You can check the McCall effect on yourself, below are the necessary images. Note: there is a chance that this will affect your vision for a while - although, for the most part, it only works when you look at vertical or horizontal lines. You decide.

So what causes it? There is no definite answer. There are three main hypotheses, the first is that something happens to the neurons in the visual cortex. The other is that the brain is trying to color the world around and come to a dead end, and the third hypothesis is that it is like a lifting effect, like a hangover from an excess of color.

There was one particularly interesting study done in 1995. In it, the researchers examined a patient with significant brain damage. According to scientists: "he could hardly distinguish colors."

After being shown black-red grids, despite the fact that he could hardly distinguish between them, the patient reported that the effect works when looking at the black-and-white grid. The researchers concluded that this effect appears outside the visual cortex, somewhere along the path from the eye to the brain.

This is confirmed by the thesis submitted by Julien Cyr at the University of Edinburgh. He wrote that "the processing mechanisms associated with EM (the McCall effect) are mainly located in the primary visual cortex, even if excitations in this area of ​​the visual system lead to a subsequent change in the activity of higher areas of the cerebral cortex."

Some studies have tried to figure out how widespread this effect is. In one of the experiments in 1969, it was discovered that any stripes painted in red and green had effects. It was also found that if you looked at the green grid, you would see a red tint on the vertical white lines, and a green tint on the horizontal ones. If you looked at the red grid, then vice versa.

What else is strange - it is the saturated red and green colors that work best. “Images with bright blue and bright yellow stripes, or pale red and pale greens, had little effect,” the study notes. As far as can be judged, there is no clear understanding of why exactly red and green colors are so good at creating the McCall effect.

Why grid? This may be due to the fact that “the neurons of the visual cortex respond best to a certain orientation and spatial frequency,” as written in one of the studies. It also offers an interesting theory based on the fact that the JPEG format uses a “checkered” structure, which consists of two grids superimposed on each other.

“Perhaps the effectiveness of this kind of visualization means that something similar is used in our brain?”, - write the researchers.

And this seems to be true. In the visual cortex, something happens and the brain is somehow deceived. The exact mechanics of what is happening is unknown, but it seems that this is a trick of the brain, not the eye.

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  • Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect


    Another tricky optical effect

    Another tricky optical effect