Why Our Brain gets Fool of Optical Illusion

A human from the Palaeolithic period carved a stone image of a mammoth or a bison 15,000 years ago in a corner of modern-day France; the fact is that the artwork symbolizes either animal depending on how it is read. Because of its resemblance to the rabbit-duck illusion, a drawing published in 1892 that is frequently recognized as one of the pioneering examples of the contemporary study of these visual illusions, its discoverer, Duncan Caldwell, has proposed that this is the oldest known case of an optical illusion. Optical illusions are now valuable tools for unraveling the secrets of perception and cognition, despite their odd character.
Optical illusions range from the most basic and well-known, such as those by Müller-Lyer, Ponzo, Ebbinghaus, and Delboeuf, which cause lines or figures of the same size to appear different when viewed directly versus their reflection in a mirror, to the amazing geometries of Japanese mathematician and artist Kokichi Sugihara, which show us radically different shapes when the objects are viewed directly versus their reflection in a mirror. Psychologist Richard Gregory separated optical illusions into physical, physiological, and cognitive categories, which were further split into fictions, ambiguities, paradoxes, and distortions by Psychologist Richard Gregory. Different mechanisms and levels of brain processing are involved in these varied impacts.
We find it difficult to believe that two squares are the same shade of grey when they are placed against different backgrounds, as in Adelson's checker-shadow illusion.

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This effect was initially discovered in the nineteenth century, and scientists have been trying to figure out whether the key to it is in our vision or our interpretation of reality, or whether it is physiological or psychological.

THE EFFECT OF SIMULTANEOUS CONTRAST

The Massachusetts Institute of Technology claims to have discovered the answer in a study. The researchers devised a modified form of a simultaneous brightness contrast in which one background appeared to be lighter while the other appeared to be darker. If we were to rely on our perceptions of brightness, the contrasted figure would appear to be darker than the second, but in fact the opposite is true. "This discovery runs opposed to the concept that high-level understanding of lighting circumstances contributes to brightness estimation," says the study's director, computational neuroscientist Pawan Sinha.
The illusion of simultaneous contrast is not dependent on binocular vision integration, and it also occurs in children with congenital blindness who have recently recovered their sight through surgery, indicating that it is not reliant on visual learning. Overall, according to Sinha, this type of optical illusion is a "low-level phenomenon" that may be located in the retina itself and does not require complex cognitive processing, contrary to what scientist Hermann von Helmholtz proposed in the 19th century. "This is something that the visual system is built to achieve from the start," he says.

BEES AND FLIES ALSO PERCEIVE THEM

The fact that other animals, including monkeys and other mammals, as well as fish, reptiles, and birds, are sensitive to some optical illusions is another hint that some of these illusions may not require a complex human brain. It's even more startling to hear that it happens in insects, which have eyes and brains that are vastly different from ours. Bees are prone to the Ebbinghaus illusion, which causes two identical figures to appear to be of various sizes based on the surrounding items, according to a study done by vision scientist Adrian Dyer of RMIT University in Australia in 2017.
Fruit flies can perceive illusions of movement, in which a static geometric pattern appears to move, according to a Yale University study led by neurophysicist Damon Clark. The impact is found in two specific neurons in the fly, and the researchers' findings suggest that the insect's brain and ours "may use similar mechanisms." Finding such connections in species so far apart in evolution shows that both have evolved comparable mechanisms, as Dyer tells OpenMind: "I believe convergent evolution is a likely explanation for why flies and humans appear to have comparable experiences with illusory motion perception." "It's probably a good bet that this is convergent evolution," Clark agrees with OpenMind.
However, if "when we experience illusions, it's because our brains form the wrong assumptions about visual patterns," as Clark says, why would such diverse animals acquire identical processes that cause them to make such errors? The plausible solution, according to the neurophysicist, is that optical illusions are side effects of valuable processes; humans' and flies' visual systems have evolved to compute light and dark contours differently in order to improve movement appreciation. "Basically, flies and humans live incomparable visual situations, and our findings suggest that their eyes may have evolved to detect motion in similar ways while dealing with light and dark in the environment."

CHILDREN ARE LESS SUSCEPTIBLE

Despite this, there is still a lot to learn about our illusory sense of perception. Elena Nava, a psychologist at the University of Milano-Bicocca in Italy, tells OpenMind about a study that demonstrated the Ebbinghaus illusion is less deceiving for youngsters "because they are more accurate at judging size when the context is misleading." Nava and Ana Tajadura-Jiménez, a computer scientists at the University Carlos III of Madrid, research body illusions that are more complex than simple visual illusions. For example, the auditory Pinocchio illusion makes us believe that a finger grows longer when we pull on it while listening to a sound that rises in pitch. Children, once again, are less vulnerable, according to the two scientists.
These body illusions, according to Tajadura-Jiménez, "involve both bottom-up multisensory integration mechanisms and other top-down processes, such as the presumption of body shape." "Illusions require the ability to integrate different inputs (whether sensory or merely visual), and youngsters are not very adept at it," Nava says. Body illusions have been observed in monkeys, according to Tajadura-Jiménez. This erratic perception of our bodies, according to the scientist, can be an evolutionary advantage: "It can be useful to adapt to new body configurations, for example, if a drastic change occurs to our body, but it can also be useful when we hold a tool and use it to operate in the environment and to guide efficiently our interactions."
   

 
 

What are 3 types of optical illusion?

Every visual illusion can be classified into one of three categories: physiological, cognitive, or literal. Let's take a look at these three groups and see which illusions fit within each of them.

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