Optical illusions, or as they are also called optical deceptions, arise in healthy people relatively often throughout life, since they are a perfectly normal condition, depending on the specific conditions or structure of the human eye.
The reasons for some illusions are established, but most of them have no scientific explanation, and to this day. Among the known types of optical illusions are the phenomena caused by the peculiarities of the structure of the organ of vision: irradiation, visual deceptions, Mariott’s illusions associated with astigmatism (the so-called blind spot), etc. Today, doctors and psychologists managed to create an unusual classification that shares all types of optical deceptive perceptions on different grounds. So, there are illusions of perceiving the size of an object or figure, the ratio of the size of the figure depending on the background, color deceptions and contrasts. And also, the erroneous perception of depth and motion, the effects of perceptual readiness and aftereffects, illusions of a paradigm direction, seeming imaginary and impossible (areal, beyond reality, unreal) figures.
Optical illusion is an erroneous visual perception of reality, an object or visible phenomenon as a result of the peculiarities of the structure of the visual apparatus, as well as under the influence of specific natural conditions (refraction of rays in heavy rain, distortion of outlines of objects or figures in twilight). Moreover, a disease such as color blindness has nothing to do with optical illusions.
For visual perception, the whole system of the visual apparatus, including the eyes, nerve cells and endings, through which the visual signal enters the brain, and directly that part of the brain that is responsible for the visual perception of phenomena or objects, is responsible for the visual perception.
An amazing phenomenon is the well-known from the time of Ptolemy, the illusion of the perception of celestial bodies in an enlarged volume when they are at the horizon line. Many scientists have found worthy and convincing explanations for this phenomenon, but time passed, and new, equally “reliable” theories appeared.
This only says that in the field of optical illusions there are many more possibilities for studying. Scientists and physicians subdivided (conditionally) the reasons for any kinds of optical illusions into three types:
– the first reason is that the visual system perceives the light reflected from objects, in such a way that the person’s consciousness receives an 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 (malfunctions of brain activity), which gives an incorrect reaction.
In some cases, an illusion can arise immediately for several reasons.
There are several types of appearance of optical illusions – optical illusions, which for not entirely studied reasons were created by nature (the most famous example being mirages in deserts) created artificially by a person using visual effects (in particular, playing with light perception).
An example is the well-known optical focus – floating in the air (levitation). No less interesting are the illusions recreated by a man based on known natural deceptions – these are mixed optical illusions – illusive visual images.
If artificially created optical illusions have a strict explanation (play with light, mechanical constructions), then a natural illusory deception practically never has a scientifically substantiated solution.
There are many examples of natural illusions, most of them related to irradiation.So, for example, if we consider squares of white and black color at a great distance, the white drawings are perceived by the larger ones, while in reality the geometric figures are the same in the pictures. Moreover, the researchers have long noticed that as the distance to the image increases, the illusion increases – this is irradiation.
This kind of illusions is due to a specific effect that arises from the peculiarity of the eye’s structure: any point of 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, , with images of black color everything happens, on the contrary. All the experiments aimed at detecting irradiation have confirmed its presence in all people.
The illusion of a “blind spot” provokes a peculiarity of the structure of the visual apparatus, or rather, the existence on the retina of the eye of a small zone in which there is no sensitivity to light. If the ray is reflected from any point of the object, it falls into this zone, then the consciousness is not able to perceive it, therefore some parts of objects seem invisible and the picture is completely distorted. Several examples perfectly illustrate the presence of this optical illusion.
When we look at the cross with the left eye on the right side of the picture, we will not see a black circle at some distance, although we will distinguish between both circles. The circle coincided with a blind spot, so the person simply does not see it, although it distinguishes two circles perfectly.
If we consider this image with a closed left eye at a distance of 20-25 centimeters, a large circle becomes invisible, but smaller circles on the sides are very well seen. And when you look at the cross at the bottom, the circle is invisible only partially. This example is called optical illusion (the illusion of Mariott).
There are examples that confirm the origin of optical illusions with astigmatism. If you look closely at the inscription made in black letters, one eye, then one of the letters will be perceived more black, if you rotate the inscription at different angles, then a deeper black color will appear different letters.
Astigmatism is expressed in different bulges (in different directions) of the cornea of the eye, this feature is practically in everyone (congenital astigmatism, recognized as a congenital disease is only in 10% of people).
There are many examples of this phenomenon, if for a long time to look with one eye at a close distance to the picture, focusing on the top white square, then soon the lower white strip disappears from the field of vision (doctors explain this by fatigue of the retina).
Another misperception of objects occurs with special types of lighting, these deceptions are called illusions of color. One of the most unique effects is an experiment with lighting – if two illuminators placed in a special way (20 cm distance) will illuminate a vertically placed object, its shadow will appear on a white screen.
After that, light 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 screen color in the perception of a person, will remain. An unusually bright and unexpected example of optical illusion, when color is imprinted in the brain, is simply a deceptive perception of sight.
There are many theories in which attempts have been made to explain this phenomenon, but we must admit that not one of them gives a complete picture of optical deception.
Violation of color perception is also considered one of the types of optical illusion, but its consequences may not be as harmless as one would expect. Road services are well aware that, according to statistics, most of the emergencies recorded at intersections at dusk.
This is due to the fact that, under reduced illumination, vision is reconstructed from a cone-shaped viewpoint to a stick-like view, in other words, from color perception to light (more sensitive). The peak time of accidents is precisely the moment of transition, when the cone-shaped receptors of the eye are turned off, and the rod analyzers are not included in the perception.
Artificial creation of optical illusions allows specialists to reveal certain patterns of visual perception, so psychologists pay great attention to experiments, tests, invented by them, serve as a “litmus test” for clarifying hidden mechanisms of vision. To do this, experts come up with all sorts of test experiments, during which the eye must solve unusual problems in unusual conditions.
The role of optical illusions has always been high, in the ancient times they were used by shamans, the pictures 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 them are optical illusion.
Studies related to geometric optical illusions, from a scientific point of view, were first conducted in 1854 by Oppel. They were engaged in Wundt, Zollner, Poggendorf, Kundt, Helmholtz. Their works tried to clarify as much as possible the nature of the optical and psychological perception of numerous illusions.
An interesting illusion is represented by circles printed on paper, which, under special conditions, starts to rotate in the mind of a person, it will be more correct to say that a person perceives them as rotating. The closer the image is viewed, the faster the circles spin. At a time when the distance is so large that the whole picture “fits” in the field of view, the circles generally stop.
In a special way placed coffee beans, also cause optical deception, it seems to the person that they move, make chaotic undulating movements, reminiscent of a person lifting and lowering the chest with inhalation and exhalation (of course, this is visual illusion, in fact, coffee beans motionless).
Refers to artificially created illusory deceptions and three-dimensional graphics, or the creation of 3d-drawings, volumetric drawings, increasingly gaining popularity throughout the world. The essence of such drawings or stereography is based on the fact that, images created with the help of 3d technology, acquire the effect of volume.
The main difference between three-dimensional images and a two-dimensional image is the transfer of the geometric projection of a three-dimensional object onto a plane using special programs. The model for creating a 3d-drawing can serve absolutely any object, real objects or natural phenomena.
The illusion of volume, created with the help of three-dimensional graphics, is widely used in architecture and construction – “living” walls, floors, “moving” facades significantly diversify the apartments and exterior of buildings.
Scientists at all times, studying optical illusions, focused, as a rule, on the psychological and medical factors of this phenomenon, and only in recent years experts have come to the unusual conclusion that the everyday natural illusions of vision can themselves influence scientific observations, introducing erroneous perception, which can lead to erroneous conclusions. Not so long ago, when studying the singularities of single crystals, specialists discovered that optical illusions constantly led to incorrect, highly distorted (25% and more) results of estimating the actual geometric parameters, in connection with which, it is necessary to check all visual observations with the help of large-scale rulers.
Moreover, almost all complex geometric shapes cause visual illusions, parallel lines, in large numbers printed on a sheet of paper, appear wavy, concentric circles begin to “move.” To the same kind of illusions are deceptions of the crooked mirrors, so familiar to all from childhood optical illusions.