Probably, every person during his life encounters non-trivial physical phenomena, not always realizing that these are illusions created by his imagination. Most often, their appearance is associated with non-standard thinking and, accordingly, a subconscious perception of real events or familiar objects viewed from an unusual angle, or under different lighting. All these conditions sometimes "play" with the human consciousness different jokes, sometimes scary, sometimes funny.
Psychologists are well aware that the "indications" of all human senses are far from always unambiguous, and also depend on all sorts of side effects and factors, including observation conditions and mood, physical and psychological state of a person.
There are a lot of illusions caused by the human sense organs today, not every of them is considered an illusion in the psychological meaning of this phenomenon, there are illusory phenomena artificially created with the help of adjusted deception (sight, hearing). These illusions are of great importance for scientific research. For example, this concerns the optical effect that each person has encountered under different circumstances, the so-called parallax.
Parallax is an apparent, imaginary displacement of objects that are actually at different distances from the observer's eyes. This relative displacement can occur with the movements of his eyes. So, for example, when observing from a train window, it seems to a person that the trees located closer, "run away" back at a higher speed than those in the distance. And the farthest trees simply "keep up" with the train. Instead, a person perceives the landscape outside the window as a picture turning around a point, while the person's gaze crosses the horizon.
An even more striking example, which is of great importance, is the manifestation of parallax when observing the change in the readings of any device, which change depending on the position of the eyes. The arrows on the background of the scale move in the opposite direction from the movement of the eyes, although in reality they show the same value. If in the store, when the goods are on the scales, take a step to the left, then the readings of the scales will visually decrease by several divisions, and, conversely, when moving to the right, the readings will increase.
There are special ways of dealing with parallax, with this harmful illusion, otherwise, all indicators of devices during experiments and when weighing will be invalid. In the manufacture of precision instruments, they try to make the arrow as thin as possible, an additional mirror strip is placed under the scale.
Every researcher knows that at the moment of reading the readings, the head must be kept in such a position so that the real arrow and its mirror reflection coincide, in this case the direction of sight will be strictly perpendicular to the scale plane, and the reading error will be reduced to zero.
Another example of an illusory psychological perception of a geometric pattern by our consciousness is the experience with a glass turned upside down and put on paper. If, outlining its edge with a pencil, draw 3 arcs (small, medium and large), then realizing that they are all drawn with the same glass, consciousness "sees" arcs with different radius of curvature.
There are many such examples - they are always found in our daily life, and often interfere, especially when conducting research and experiments, since a distorted picture of reality does not give the correct result. More serious illusory errors arise when comparing volumes or areas (while the trained eye can estimate the linear dimensions correctly). These psychological illusions are on the verge of psychology and optical (visual) deception.
These include the well-known irradiation - black and dark objects are always perceived as smaller in size than light or white ones. This psychological illusion is perfectly used by fashion designers, creating models for obese people from fabrics of a dark color, decorating them with a bright color spot that distracts the eye.
Very often psychological illusions are associated with movement - a pendulum swinging against a dark background takes on the shape of an ellipse in the human mind, elongated in the direction of movement, if you look at it simultaneously with two eyes (if you close one eye, the pendulum will swing illusoryly in the other direction). If you focus on the light thread of the suspension, then the pendulum will swing even faster - this is again due to the fact that a person's eyes notice light objects faster than dark ones.
If the eye is closed with glass (glasses), then the swinging pendulum has a movement slightly lagging behind the real one (two eyes see the real swinging speed). In this case, the consciousness will perceive the movement as volumetric (in reality, the pendulum is swinging along a flat trajectory). These illusions are also harmful, because they greatly interfere with the study of objects that scatter light in different ways (in different directions).
Oddly enough, but if the structure of the human eye has been studied almost thoroughly, then the mechanism of vision itself turned out to be so complex that there is no final decision and conclusions of scientists yet. This can be easily explained by the fact that the brain takes a large part in the process of perceiving the surrounding world with the eyes. This "commonwealth" is the main reason for the emergence of psychological illusions when a person's attention is switched, a sudden change in lighting or angle of view.
Experts are well aware of the example of an "everting cube" - a person perceives the facets facing him in different ways, which is directly related to which of them the human gaze is focused on. Human perception of the environment is capable of amazing things, and above all, "see" a completely different picture than the one that a person is going to see.
This ability extends to a very large part of phenomena and events, scientists involved in the psychology of illusory perception, only state many examples, and in their definition they strongly disagree.
There are many well-known psychological illusions, the appearance of which depends on the creative potential of a person, his psychological momentary state, illumination and other psychological reasons (we are talking about illusions that arise in the mind of a healthy person). These include the illusory perception of the shape of spots on the moon (for some they resemble figures, for some they see human faces, etc.).
There is a well-known illusion when a real phenomenon or object unexpectedly "changes" its size and shape - for example, having suddenly opened your eyes after sleep, you can see a huge beast in a familiar wallpaper pattern (if you finally wake up, the beast turns out to be an ordinary fly).
Human hearing is also subject to psychological illusions, probably everyone found themselves in a position where the distant rumble seemed like a thunderous rumbling, and the squeak of a mosquito above the ear was a frightening cry, or a telephone alarm call. Moreover, anxiety and fear are much more often accompanied by psychological illusions, especially auditory. Psychologists associate this with the subconscious expectation of any person for bad news, and any non-standard situation causes negative feelings in him.
In addition, a person perceives an incomprehensible and unexpected sound psychologically, as a danger, since he does not have exact information about it, and does not realize the real distance to its source. There is one more feature of psychological perception - depending on which ear the sound signal enters into, a person perceives its location differently.
And if the sound entered both ears at the same time, then the consciousness can perceive the source as being directly in its head, or next to itself. Not every blindfolded person can accurately determine the source of external sound, moreover, in a different psychological state, a person defines it differently, and recognition errors are of a different nature.
The illusions of touch are completely unexpected. If you exclude vision from perception, blindfold, and hold it over your own nose, then the illusion may arise that there are two of them. Such psychological illusions are associated with a different arrangement of fingers relative to each other, therefore they "feed" different information to the brain, and consciousness perceives them, as usual - in this regard, illusory and different pictures appear (in this case, one finger "reports" about one nose, and the other about the other).
A common reason for the emergence of a psychological illusion is an unusual (or unfamiliar) combination of sensations inherent in different senses. If the same amount of water is poured into a balloon and a glass jar, then a person will not be able to raise the balloon on the first attempt, since he will make insufficient effort (calculated for the lightness of the balloon), the reason is an illusory perception, which misleads the mind.
Everyone knows the psychological illusions associated with the work of the vestibular apparatus. After a long ride on a swing, the earth continues to rotate for a long time (the rotation time and speed depend on the individual state of the vestibular apparatus).
A cyclist descending a steep slope perceives it as more sloping, noting the nearest landmarks with his eye. Each person has probably experienced the illusory sensation of continuing to move while standing on an escalator that suddenly stops. Despite the fact that the eye sees that the steps are already motionless, the body continues to lean forward, as if moving a ladder.
So psychologists argue that the occurrence of illusions can often arise due to the prevailing stereotypes, even if the phenomenon seen in reality runs counter to the already familiar signal to the brain. The conclusion of psychologists and scientists is the same - the reasons for the emergence of psychological illusions are most often associated not so much with psychophysiological phenomena, but with physical incorrect perception of the brain (and, accordingly, an erroneous signal).