October 20, 2020

Why optical illusions ‘trick’ your brain – La Provincia


One hundred years has taken to resolve a mystery about two gray dots that are identical, but they seem very different depending on where they are placed relative to the background. In other words: if a shape is surrounded by something dark, we perceive it as brighter than if it were in lighter shadows. It is known as “simultaneous brightness contrast” for which an answer seems to have been found.

Also six years ago, in 2014, another optical illusion puzzle was deciphered that Galileo Galilei detected four centuries ago.

In the first case, a study of Massachusetts Institute of Technology (MIT) suggests that this kind of ‘visual puzzle’ is based on estimating the brightness that takes place before the information reaches the visual cortex of the brain. In this sense, they suggest that it is possibly within the retina.

In the second, the astronomer observed that, when looking at some planets, at first glance they appear to be larger than they really are. Almost four hundred years later, a team from the State University of New York discovered that behind this visual effect is found to a different neural response to light and dark colors.

So why do these visual illusions ‘trick’ our brain? A recent study in which a group of 27 volunteers underwent visual tests to test whether our interpretation of what we see is due to shadows or actual levels of light emitted, notes that “the side that was actually brighter was perceived as darker and vice versa.”

That a point on a dark background appears brighter than another on a light background is explained by the luminance, defined as the angular, rectangular and superficial density of the luminous flux that impinges, crosses or emerges from a surface following a certain direction.

Well, it turns out that luminance contributes to our brightness estimates, suggesting, according to the study, that high-level thought processes are not required to perform this kind of ‘visual judgment’ in which a point seems brighter to us. that other.

Also, the researchers discovered that all of these brightness estimates we make are a kind of innate mechanism. That is, they occur before the information from both eyes merges into the brain.

This perception, therefore, is not learned over time nor is it influenced by the past experiences of each person, but the visual system it is prepared like this from birth.

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