What are optical illusions?
Optical illusions, are also known as visual illusions, involves deception. Images arranged in unexpected ways, colors that trick the eye, or the impact of light sources can all produce an array of misleading visual effects.
It may have occurred to you that not everyone experiences visual illusions in the same way, if you’ve ever had trouble seeing the hidden image in a stereogram. It is possible that some people will not see an illusion’s effect.
The workings of the brain can be revealed by optical illusions, which can be both fun and amusing. It is thought that the mammoth was carved out of stone in a corner of present-day France about 15,000 years ago by a human from the Paleolithic period. The piece may represent either animal, depending on the interpretation.
A drawing by Duncan Caldwell published in 1892 that has been cited as an early example of the modern study of these optical illusions suggests that this might be the oldest known optical illusion because of its similarity with the rabbit-duck illusion, regarded as a pioneering example. Nowadays, optical illusions are more than just a curiosity. They help understand the complexities of perception and cognition.
Müller-Lyer, Ponzo, Ebbinghaus, and Delboeuf are some of the simplest optical illusions, which cause us to perceive lines or figures that are the same size as each other to appear different. Kokichi Sugihara, a Japanese mathematician and artist, creates amazing geometrical structures that change drastically when viewed directly, compared to when reflected in mirrors.
According to Richard Gregory, optical illusions break down into physical, physiological, and cognitive categories, which are further subdivided into fictions, ambiguities, paradoxes, and distortions. It is important to note that each of these effects involves distinct mechanisms and requires different levels of neural processing.
The most surprising illusions also exploit the same effect, simultaneous contrast. When we see two squares against contrasting backgrounds, our perception of their color is affected, as in Adelson’s checker-shadow illusion. Scientists have been researching this phenomenon since the 19th century, trying to figure out whether it is a physical or psychological effect that arises as a result of our vision or perception of reality.
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Contrasts occurring simultaneously
Harvard University argues that it has found the answer in a study. An altered version of a simultaneous brightness contrast was prepared by the researchers in which a seemingly lighter background in reality may be darker. If we look at the brightness of both figures, we would expect the second figure to be darker than the contrasting one, but we would be wrong.
According to the study’s director, Pawan Sinha, “this result contradicts the estimate of brightness based on high-level analysis of lighting conditions. Furthermore, the scientists have demonstrated that simultaneous contrast does not rely on binocular vision integration, and that it also occurs in children whose sight has just been restored after surgery for congenital blindness, so it is not a visual learning phenomenon.
Sinha concludes that optical illusions like these are low-level phenomena, occurring within the retina itself, and do not require complicated cognitive processing as Hermann von Helmholtz predicted in the 19th century. He asserts, “the visual system is more than capable of performing this task from birth onward.”
The effect of simultaneous contrast is explained by an inhibition of receptors in the retina that aid us in exaggerating differences in luminance to better perceive our environment, according to vision scientist Michael Bach, professor emeritus at the University of Freiburg and author of an extensive web catalog of optical illusions.
The same effect of contrast can be seen in an illusion created by Japanese psychologist Akiyoshi Kitaoka in 2015, in which the strawberries on a cake appear red, even though their color is grey, when viewed against a blue background. Also, I would place a large portion of the strawberries on the retina. Assuming it’s a white balance effect, Bach explains that it influences the whole retina and not just local areas.
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Fly and bees perceive them too
It has been demonstrated that monkeys, fish, reptiles, and birds are all sensitive to certain optical illusions, suggesting they don’t require a complex human brain to perceive them. Moreover, it occurs in insects that have so different eyes and brains than humans.
The Ebbinghaus illusion occurs when two equal figures are viewed as being of different sizes depending on the surrounding objects, and was discovered in 2017 by vision scientist Adrian Dyer at RMIT University in Australia.
Scientists at Yale University have discovered that fruit flies are also able to perceive movement when they see geometric patterns that move. Their experiments suggest that flies’ brains employ similar mechanisms to ours by locating the effect in two specific neurons.
Having such similarities between species so far apart in their evolution suggests that both species have evolved similar mechanisms, Dyer tells: “Convergent evolution may have contributed to the illusory motion perception observed in flies and humans”. The possibility of convergence is also a good bet for Clark, he tells. “There may be a set of mechanisms in the brain that can enable such similar functions in humans and in flies.”
Dyer does not rule out, however, that the two taxa share common ancestry: “There may be processes in the brain that enable such a function.” Clark suggests that “our brains make incorrect inferences about visual patterns when we see illusions,” but why would species with such disparate characteristics develop similar mechanisms that make them make such errors?
The common solution, according to the neurophysicist, lies in the fact that optical illusions are a consequence of vital processes; for example, flies’ visual systems have evolved to compute light and dark contours differently in order to improve their ability to perceive motion. We found that fly eyes and human eyes deal with light and dark in environments in similar ways when detecting motion.”
“Flies and humans inhabit similar visual environments, which suggests they may have evolved similar methods for dealing with light and dark. Clark states that “most of the time, these types of inferences are beneficial for our natural vision to make.” An illusion is a pattern that leads to mistaken perception.
The concept of visual illusions may be attributed to brains using statistical regularities in the world to draw inferences about the world around them, and this may be the same phenomenon that all of these common illusions are instances of: brains making inferences based on the typical arrangement of the visual world.”
Children are less vulnerable
The illusionary sense of perception remains a largely unexplored phenomenon. A psychologist at Milan’s Bicocca University, Elena Nava, talked about her study which suggested that kids get a better sense of size when context is misinforming, so the Ebbinghaus illusion is less of a deception for them.
From the University Carlos III of Madrid, Nava and Ana Tajadura-Jiménez study body illusions, which are more complex than just visual illusions. Pinocchio’s auditory illusion, for instance, makes people think if they pull on a finger while listening to a high pitch sound, the finger gets longer. Once again, children seem less susceptible to the magic.
Specifically, Tajadura-Jiménez explains, these body illusions are caused by both multisensory integration mechanisms at the bottom-up level and top-down processes, such as thinking about body structure. Children do not do very well at integrating different cues (sensory or visual) and that is a complex process that develops with age, according to Nava.
Tajadura-Jiménez points out that monkeys have shown body illusions as well. It is also possible for this fickleness in our perception of our bodies to serve as an evolutionary advantage, according to the scientist: “It can be helpful when we are adapted to new body configurations, for example, if our bodies undergo a drastic change, as well as when we hold a tool and use it in an environment, guiding our interactions efficiently.”
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Illusions of psychiatric significance
It is not uncommon for children to perceive threatening faces or monsters in shadows or see goblins in trees as a result of feelings of anxiety or fear projected onto external objects. A soldier seized by fear may mistake an inanimate object or a comrade for an enemy. During Don Quixote’s time, windmills were viewed as enemies. There have been cases where psychiatric patients have viewed people as machines, teddy bears, and devils.
What happens when one experiences déjà vu is a fusion of past and present so that they believe they are reliving a past experience and therefore know how it will turn out. An experience of familiarity is called a “hallucination”; some theorists suggest that it is a result of reactivating old memory traces triggered by stimuli reminiscent of the past — for example when one finds a pressed rose in a long-forgotten dance program, that old memory may flood back.
Often in everyday life, illusional misperception is caused by strong emotions, powerful associations, and strong expectations. Those who hear “wire” may think someone is calling them a “liar”; those who are overly conscious of their weight may hear “fate” as “weight”. Similarly, people can be mistakenly identified. Tom may appear to be Gary, either because John wants to avoid Tom or he is seeking Gary.