Optical illusions


Optical illusions, or as they are also called optical illusions, occur in healthy people relatively often throughout their lives, since they are a completely normal condition, depending on the specific conditions or structure of the human eye.

The reasons for some of the illusions have been established, but most of them have no scientific explanation, to this day. The known types of optical illusions include phenomena caused by the structural features of the organ of vision - these are irradiation, optical illusions, the Mariotte illusion accompanying astigmatism (the so-called blind spot), etc.

Today, doctors and psychologists have managed to create an unusual classification that divides all types of optical illusion according to different characteristics. So, there are illusions of perception of the size of an object or figure, the ratio of the size of a figure depending on the background, deceptions of colors and contrasts. And also, erroneous perceptions of depth and movement, the effects of perceptual readiness and aftereffects, illusions of the pareidolic direction, seeming imaginary and impossible (areal, beyond reality, not real) figures.

An optical illusion is an erroneous visual perception of reality, an object or a visible phenomenon as a result of the structural features of the visual apparatus, as well as under the influence of specific natural conditions (refraction of rays in heavy rain, distortion of the outlines of objects or figures at dusk). Moreover, such a disease as color blindness has nothing to do with optical illusions.

The entire system of the visual apparatus is responsible for visual perception, including the eyes, nerve cells and endings, thanks to which the visual signal enters the brain, and directly that part of the brain, which is responsible for the visual perception of phenomena or objects.

An amazing phenomenon is the illusion of perception of celestial bodies in an increased volume, known since the time of Ptolemy, at the moment they are near the horizon. Many scientists have found worthy and convincing explanations for this phenomenon, however, time passed, and new, equally "reliable" theories appeared.

This only suggests that in the field of optical illusions there are many more opportunities for study. Scientists and doctors have divided (conditionally) the reasons for any types of optical illusions into three types:

- the first reason is that the visual system perceives light reflected from objects in such a way that the human consciousness receives erroneous (imaginary) information.

- the second reason is the erroneous, incorrect transmission of visual signals through the nerves, as a result, the brain also receives incorrect information, which leads to an imaginary, distorted perception.

- the third reason is based on brain disorders (brain malfunctions), which gives an incorrect reaction.

In some cases, an illusion can arise for several reasons at once.

There are several types of the appearance of optical illusions - optical deceptions, which, for reasons not entirely studied, were created by nature (the most famous example is mirages in the deserts), created artificially by humans, using visual effects (in particular, playing with light perceptions).

An example is the well-known optical focus - hovering in the air (levitation). No less interesting are the illusions recreated by man according to well-known natural deceptions - these are mixed optical illusions - visual illusion pictures.

If artificially created optical deceptions have a strict explanation (play with light, mechanical constructions), then natural illusory deception almost never has a scientifically substantiated solution.

There are many examples of natural illusions, most of them related to irradiation. So, for example, if we look at squares of white and black at a great distance, then white drawings are perceived by a person as larger, despite the fact that in reality the geometric figures in the pictures are the same. Moreover, researchers have long noticed that as the distance to the picture increases, the illusion intensifies - this is irradiation.

This type of illusion is due to a specific effect that arises due to the peculiarities of the structure of the eye - any point of a light tone is "imprinted" on the retina in the form of a circle (spherical aberration), and the perimeter of this circle is bordered by a light ribbon, due to which the surface increases, with images of black color everything happens the other way around. All experiments aimed at detecting irradiation have confirmed its presence in all people.

The illusion of a "blind spot" is provoked by the structural feature of the visual apparatus, or rather, the existence of a small zone on the retina of the eye, in which there is no sensitivity to light. If the ray reflected from any point of the object hits this particular zone, then the consciousness is not able to perceive it, therefore some parts of the objects seem invisible and the picture is completely distorted. Several examples perfectly illustrate the presence of this optical illusion.

Examining the cross on the right side of the picture with our left eye, we will not see a black circle at some distance, although we will distinguish both circles. The circle coincided with the blind spot, so a person simply does not see it, although he perfectly distinguishes between two circles.

If we consider this image with the left eye closed at a distance of 20-25 centimeters, then a large circle becomes invisible, but smaller circles on the sides are very clearly visible. And when looking at the cross located below, the circle is only partially invisible. This example is called optical illusion (Mariotte illusion).

There are also examples confirming the origin of optical illusions in astigmatism. If you carefully look at the inscription made in black letters with one eye, then one of the letters will be perceived as blacker, if you rotate the inscription at different angles, then different letters will appear deeper black.

Astigmatism is expressed in different bulges (in a different direction) of the cornea; this feature is present in almost every person (congenital astigmatism, recognized as a congenital disease, is present in only 10% of people).

There are many examples of this phenomenon, if you look at the picture with one eye at close range for a long time, focusing on the upper white square, then the lower white stripe will soon disappear from the field of view (doctors explain this by retinal fatigue).

Another misperception of objects occurs with special types of lighting, these deceptions are called color illusions. One of the most unique effects is the experiment with lighting - if two lights placed in a special way (distance 20 cm) illuminate a vertically placed object, its shadow will appear on a white screen.

After that, filters of different bright colors (for example, blue and red) are put on both lamps - these colors will also be reflected on the screen. But ... if you remove one color filter, then the color in the perception of a person will remain on the screen. An unusually vivid and unexpected example of optical illusion, when color is imprinted in the brain, it is simply a deceptive perception of vision.

There are many theories in which attempts have been made to explain this phenomenon, but we have to admit that none of them gives a complete picture of optical deception.

Color disturbance is also considered a type of optical illusion, but its consequences may not be as harmless as one might expect. The road services are well aware that according to statistics, most of the accidents were registered at intersections at dusk.

This is due to the fact that under reduced illumination, vision is rearranged from cone vision to rod vision, in other words, from color perception to light (more sensitive). The peak time of accidents is precisely the moment of transition, when the cone receptors of the eye are turned off, and the rod analyzers are not included in perception.

Artificial creation of optical illusions enables specialists to identify certain patterns of visual perception, therefore psychologists pay very much attention to experiments, tests invented by them serve as a "litmus test" for elucidating the hidden mechanisms of vision. To do this, experts come up with all sorts of test experiments, during which the eye must solve complex problems in unusual conditions.

The role of optical illusions has always been high, in ancient times they were used by shamans, the paintings of the world famous Leonardo da Vinci are full of hidden optical illusions (he also owns several treatises on the topic of illusions). The Leaning Tower of Pisa "falls" visually only by 10% for reasons related to construction, 90% of which is an optical illusion.

Research related to geometric optical illusions was first carried out scientifically in 1854 by Oppel. They were dealt with by Wundt, Zolner, Poggendorf, Kundt, Helmholtz. Their work tried to clarify as fully as possible the nature of the optical and psychological perception of numerous illusions.

An interesting illusion is represented by circles drawn on paper, which, under special conditions, begin to rotate in a person's mind, it would be more correct to say that a person perceives them as rotating. The closer you look at the image, the faster the circles rotate. At the moment when the distance is so great that the entire picture is "placed" in the field of view, the circles stop altogether.

Coffee beans placed in a special way also cause optical illusion, it seems to a person that they are moving, make chaotic wave-like movements, reminiscent of raising and lowering a person's chest during inhalation and exhalation (of course, this is a visual illusion, in fact, coffee beans are motionless).

It refers to artificially created illusory deceptions and three-dimensional graphics, or the creation of 3d-drawings, volumetric drawings, which are increasingly gaining popularity all over the world. The essence of such drawings or stereography is based on the fact that images created using 3d technology acquire a three-dimensional effect.

The main difference between three-dimensional pictures and a two-dimensional image is the transfer of the geometric projection of a three-dimensional object onto a plane using special programs. Any object, real objects or natural phenomena can serve as a model for creating a 3d drawing.

The illusion of volume, created using three-dimensional graphics, is widely used in architecture and construction - "living" walls, floors, "moving" facades significantly diversify apartments and building exteriors.

Scientists at all times, studying optical illusions, have focused, as a rule, on the psychological and medical factors of this phenomenon, and only in recent years have specialists come to the unusual conclusion that natural illusions of vision existing in everyday life can themselves influence scientific observations, introducing erroneous perception , which can lead to erroneous conclusions.

Not so long ago, when studying the features of single crystals, experts found that optical illusions constantly led to incorrect, highly distorted (25% or more) results of assessing the actual geometric parameters, and therefore, it is necessary to check all eye perceptions using scale rulers.

Moreover, almost all complex geometric shapes cause visual illusions, parallel lines, in large quantities applied to a sheet of paper seem wavy, concentric circles begin to "move". The deceptions of crooked mirrors, optical deceptions so well known to everyone from childhood, belong to this type of illusion.


Watch the video: Optical illusions that make you feel like youre flying


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