How do you understand what perceptual illusions are. What is the illusion of perception. Visual illusions - psychology

Perception -

1) the mental process of a holistic reflection of objects and phenomena of the surrounding world, acting on the senses at the moment;

2) subjective image of an object, phenomenon or process that directly affects the analyzer or system of analyzers (perceptual image);

3) the process of forming this image or a system of actions aimed at familiarizing oneself with an object that affects the senses.

In the process of receiving and processing by a person of various information entering the brain through the sense organs, a fusion, or synthesis, of sensations into a single perceptual image takes place. At the same time, the image of perception is created on the basis of the analysis and synthesis of individual properties and qualities, the subject of highlighting essential features and abstraction from non-essential ones.

In addition to sensations, the process of perception involves past experience, the processes of understanding what is being perceived, and mental processes of a higher level (memory, thinking). The process of perception includes motor components: palpation of objects and eye movement; singing sounds or pronouncing speech forms; sniffing, etc. Perception is directed by motivation and has a certain affective-emotional coloring.

Illusions of perception - a distorted reflection of reality, which is stable. The illusion of perception is a phenomenon of perception that exists only in the human head and does not correspond to any real phenomenon or object. They can occur in different modalities. Their greatest number is observed in the field of vision. Visual illusions are diverse:

1) illusions associated with the structural features of the eye. So, white objects appear larger (see note ""):

2) illusions associated with the overestimation of the size of vertical segments compared to horizontal ones when they are actually equal:

3) illusions due to contrast. The perceived size of a figure depends on the environment. The circle seems large among small circles and smaller among large ones (Fig. 1):

4) the illusion of transference. This means transferring the properties of the whole figure to its individual parts. This is the Muller-Lyer illusion (Fig. 2) and others:

5) illusions of distortion of the direction of the lines under the influence of other lines of the background (Fig. 3):

Another type of perceptual illusions are illusions of visible movement:

1) autokinetic movement - chaotic movement of an objectively stationary light source observed in complete darkness (see note "");

2) stroboscopic movement - the impression of the movement of an object during the rapid sequential presentation of two motionless stimuli in close proximity (movie image);

3) induced movement - the apparent movement of a stationary object in the direction opposite to the movement of the surrounding background (Fig. 4).

In the realm of touch, Aristotle's illusion is well known. If we cross our index and middle fingers and at the same time touch them to a ball or pea (roll them), then we will perceive not one ball, but two.

Illusions can also arise under the influence of immediately preceding perceptions. Such, for example, are the contrasting illusions observed during the development of a “setting” according to the method of D. N. Uznadze. After repeated perception of objects that are very different (by weight, size, volume, etc.), objects that are equal in the same respect are perceived by a person as unequal: an object that is located in the place of a previously perceived smaller object seems large, etc. Contrasting illusions are often are also observed in the field of temperature and taste sensations: after a cold stimulus, a thermal stimulus seems hot; after the sensation of sour or salty, the sensitivity to sweet increases, etc.

Non-visual illusions include the Charpentier illusion: of two objects of equal weight, but different sizes, the smaller one seems heavier.

The reasons causing illusions of perception are diverse and not clear enough. Some theories explain visual illusions by the action of peripheral factors (irradiation, accommodation, eye movements, etc.), others - by the influence of some central factors. Sometimes illusions appear due to the action of special conditions of observation (for example, with one eye or with fixed axes of the eyes). A number of illusions are due to the optics of the eye. Of great importance in the emergence of visual illusions of perception is the systemic effect of temporary connections that have developed in past experience, which, for example, explains the illusion of likening a part to a whole: usually, if the whole is larger, then its parts are also larger (compared to similar parts of another, smaller whole), and conversely, if any of these parts is less, then the whole is less. Illusions of contrast can be explained by inductive relations of excitation and inhibition in the cerebral cortex. Visual illusions of perception are widely used in painting and architecture.

From the materials that were discussed in the previous paragraphs of the chapter, it becomes clear that perception is a complex process, and the images of perception, although they allow a person to navigate in space and time in order to solve vital tasks for him, nevertheless represent subjective formations, the relationship of which with reality is problematic and has not yet been fully studied. Even from those few facts that were presented and described in the previous paragraphs of the chapter, we can conclude that the images that arise in the process of perception do not always fully correspond to reality, may not reflect it, and even significantly distort it. We were able to verify this by the examples of the discussion of auditory illusions in the previous paragraph of the chapter, and we will verify this again from the content of this, the last paragraph of the chapter, where various illusions of perception are presented and discussed. This section is devoted not only to perceptual illusions as such, their description and representation, but also to possible scientific explanations of the corresponding illusions.

During the study of human perception, especially visual, a large number of various illusions have been established and described. They are presented in the works of many scientists, starting from ancient times 1 . Some of them have author's names and in the history of psychology are marked by the names of the people who first discovered, described or explained them. Most of the illusions presented in the scientific and popular literature relate to visual perception, although many illusions are known concerning all types of perception, including hearing, movement, time, skin and other types of perception.

The fact that visual illusions have attracted the most attention is due to the following reasons. First, visual illusions are the easiest to detect. The presence of such illusions can be established by touching, for example, the corresponding object with your hands and comparing your tactile sensations with visual ones. If the sensations received from touching an object do not correspond to the visual image of the corresponding object, then we conclude that its image is illusory or distorted (historically, we usually trust our tactile sensations more than, for example, visual, and everything we see, we strive to check by touch). Secondly, visual illusions are more common in life than others, and people have been convinced of their presence since ancient times. Thirdly, visual illusions are the most obvious, since it is easy to verify their existence using other senses.

Many facts indicate that, even if a person knows about the existence of a particular visual illusion, he is still not able to completely get rid of it, and most importantly, it does not prevent him from living and navigating well in the surrounding reality, skillfully adapting to it. We will soon be able to verify this on the examples of visual illusions given below.

For some well-known illusions, more or less satisfactory scientific explanations already exist, although many of these explanations are not convincing. A number of illusions still do not have a satisfactory scientific explanation. Nevertheless, acquaintance with them is not only interesting (informative and fascinating), but also useful for a deeper understanding of visual perception and the generation of a picture of the real world in the human mind. Knowledge of the illusions of perception and familiarity with their scientific explanations contributes to the development of science and allows scientists to pose and solve the following additional questions.

• 1. How accurately does a person's perception reflect reality?
• 2. How does human perception function, forming images of perceived objects?
• 3. How are the images generated by perception related to reality?
• 4. To what extent can a person's perception and the emerging picture of the world be trusted, given the fact that there are a huge number of illusions?

In order to answer these questions, we turn to the acquaintance and discussion of the most famous visual illusions. Consider first the most

A number of illusions of perception are already described in the works of Aristotle.

the simpler ones, and then the more complex ones, relating, respectively, to the visual perception of planar and spatial objects. We will then discuss some of the illusions of motion perception and auditory perception (in addition to those presented and discussed in the previous paragraph of the chapter).

Often, when perceiving simple contour or hatched images, as well as the corresponding elements of real objects and phenomena, a person may experience illusory distortions of visual images of their lines and contours. Pa fig. As an example, Figure 2.26 presents two simple illusions regarding the perception of the relative length of vertical and horizontal lines connected to each other at right angles.

Rice. 2.26.

The two lines shown in Fig. 52 a, are in fact equal, and this can be verified by measuring them with a ruler. However, the vertical line still appears to the observer to be longer than the horizontal line. In turn, the two lines shown in Fig. 52 b, appear to the observer the same, while in fact the horizontal line is longer than the vertical one. These illusions show that when comparing the length of vertical and horizontal lines formed by various objects, a person, in principle, can be mistaken, and it is almost impossible to get rid of errors - the corresponding illusions of perception, even if a person knows in advance that what he sees is illusion.

The following figure (Figure 2.27) shows a simple visual illusion known as Illusions PonzoC

The essence of this illusion lies in the fact that the intersection of two parallel segments of a straight line by other, non-parallel straight lines emanating from one point will create an illusory impression regarding the apparent length of these segments. Two parallel segments of a straight line, which in Fig. 2.27 are located at different heights, they seem to the observer to be the same in length, while in fact the lower segment is longer than the upper one. From the existence of this and other similar illusions, it follows that a person can make mistakes in estimating the length of parallel segments of a straight line if they are intersected by non-parallel lines emanating from the same point.

This illusion was discovered and described in 1913 by Mario Ponzo.

Rice. 2.27.

The same is shown by the following illusion, which arises during the perception of Fig. 2.28 (Muller illusion - Layer).

In this case, two equal segments of a straight line, enclosed in other diverging or converging lines, seem to the observer to be unequal, namely: the segment on the left appears to be longer than the segment on the right. From this we can conclude that straight lines diverging in different directions from the ends of the segment, as it were, lengthen this segment in the perception of the observer, and converging, on the contrary, shorten it (the Muller-Lyer illusion is somewhat similar to the Ponzo illusion, but complements it with the above clarification).

Figure 2.29 shows another version of a similar visual illusion associated with the influence of some lines on the perception of other lines intersecting with them.

On the left side of Fig. 2.29 shows that straight lines fanning out in different directions from one point distort the perception not only of the length of the straight line segments intersecting with them, but also of other figures, for example, a circle. In this case, it seems to the observer to be an uneven closed line, and not a geometrically precise circle. The right side of the same figure shows that the system of concentric circles, in turn, affects the perception of the square inscribed in them. Its sides as a result of their intersection by concentric circumferential

Rice. 2.28.

Rice. 2.29. Distortion of the shape of a circle perceived against the background of a field with radial lines (a); distortion of the square on the foyer of the field with concentric circles ( 6 )

The lines appear to the observer to be curved, although they are in fact straight lines.

The illusions described above suggest that, at least when we have to perceive individual simple lines intersecting with other relatively simple lines (straight or not straight), we can make mistakes in estimating their relative length. However, these errors are not so significant as to seriously impede the possibility of practical actions in relation to the objects to which these lines belong. This fact, however, does not relieve scientists from the need to seek explanations for such illusions.

Let's imagine some other variants of the simplest visual ( optical) illusions (Fig. 2.30).

Rice. 2.30.a - Ebbinghaus illusion; b - illusion, manifested in the evaluation of the figure as a whole; in - illusion of contrast; G - perspective illusion; d - parallelogram illusion; e - parallel line illusions

Illusion a(birds) is manifested in the fact that the distance between the noses of two birds, represented on the right and as if flying in different directions, seems to the observer to be the same as the distance between two birds flying in the direction of each other, although in reality the distance between the first is much greater, than between the latter.

Side of the left triangle in - from seems larger than the side of the right triangle With - d, although in reality they are equal.

In illusion b the width of the lower, straight part of the left "bowl" seems to the observer to be greater than the width of the lower part of the right "vessel". In fact, everything is just the opposite: the bottom of the right “vessel” is much wider, and not the left “bowl”.

The illusion in shows that the same size circle, enclosed in circles of different sizes, can be perceived as not being the same. In particular, a circle framed by small circles appears to the observer to be larger than the same circle enclosed in circles larger than him.

Illusions G and e(left side of the figure) indicate that when parallel lines intersect with non-parallel ones, an illusory impression is created that the intersected lines are also non-parallel. If a straight line going obliquely (the right side of the figure) crosses parallel lines, then the intersecting line is already perceived not as a straight line, but as a broken one.

Illusion d indicates that two seemingly identical lines: A - F and F - D, included in the parallelogram, are actually different, and the line F - D is much longer than the line A - F. This can be easily verified by measuring them length in the picture.

A curious illusion is the broken lines depicted on the right in that part of the figure marked with the number e. Three broken lines inclined at a smaller (acute) angle to the horizon seem more “broken” than the two lines between them that form with the horizon a larger angle (in this case, almost a straight line). In reality, the "brokenness" of all these lines is the same.

The next few visual illusions show that not only the perception of individual lines, but the whole pattern can be distorted if intersecting parallel or non-parallel lines are included in it.

fig. 2.31 presented J. Fraser illusion, which shows that parallel lines formed by alternating white and black stripes crossing these lines at oblique angles, against the background of a cellular pattern, seem to the observer to be significantly distorted, i.e. curved and therefore not parallel.

Rice. 231.

against the background of a pattern formed by intersecting diagonals, straight lines appear curved. This illusion got its name because it can be experienced by looking at a twisted rope against a background of a checkered structure.

Figure 2.32 shows another visual illusion - Münsterberg illusion. It is also impressive and indicates that parallel horizontal lines appear non-parallel if they are crossed by stacked vertical columns of parallelograms. Moreover, these columns themselves appear uneven to the observer, although in reality they are even and located strictly vertically.

Rice. 232.

the edges of all rows of a pattern formed by alternating white and black rectangles appear non-parallel

It has also been established that if there is a contrast in the drawing, its white and black parts can mutually influence each other, respectively, illusoryly “lightening” or “darkening” each other. One such illusion is shown in Fig. 2.33.

Rice. 233.

White stripes separating the black squares on the left side of figure 2.33 a, do not contain any shadows. However, it seems to the observer that there are blackouts at the intersections of the white stripes. They, apparently, are generated by the influence of black squares and a bright, black and white contrast between the individual parts of this drawing.

A similar phenomenon is noted in relation to the right side of this figure, in which the color of the stripes and squares is opposite to that presented in the left side of the figure: the stripes in this case are black, and the squares are white. It seems to the observer that there are lightened areas at the intersections of the black stripes, although these stripes themselves are black.

A series of well-known visual illusions is called subjective contours. This name refers to the illusory perceived by the observer contours of figures depicted on a plane, although in reality there are no such complete and complete contours in the drawings.

In figure 2.34, a and b, the subjective contours of the triangles are presented. When the observer examines the part of the figure marked with the letter a, it seems to him that there is a complete white triangle in the center of the corresponding figure, although in reality significant parts of its sides are absent from the figure itself (the observer, however, perceives them as real).

Rice. 2.34.

The same applies to the part of Figure 2.34 marked with the letter b. Here the observer sees a complete black triangle, although in reality it is also incomplete, and its sides are only partially represented in the figure - small segments of straight lines immediately adjacent to the corners.

Similar illusions arise when perceiving the figures depicted in fig. 2.35.

In this figure, considering it sequentially, from top to bottom and from right to left, the observer sees non-existent contours of circles, triangles, squares (the first two upper groups of figures), the contours of small squares at the intersections of straight lines (lower left figure) and the illusory contour of an oval in the center of the lower , right figure.

Rms. 2J5. Subjective contours of various geometric shapes

Some scientists suggest that the presence of illusions of subjective contours is an illustration of the operation of the principles of gestalt in the field of visual perception, in particular, the principle of integrity, according to which the image of a perceived object appears immediately as a whole, even in the absence of many elements necessary for its complete construction. However, this is an incomplete and not the only possible explanation for this kind of illusion. In addition, as is known from the paragraph of this chapter where theories of perception were discussed, Gestalt psychology of perception as a scientific theory, together with the principles of gestalt postulated in it, has many shortcomings and in itself needs to be revised.

The viewer is greatly impressed by the last of the series of illusions considered in this paragraph and presented in Fig. 2.36.

Rice. 2.36.

In this figure, the viewer clearly sees the cube (Necker cube), moreover, it perceives it completely, despite the fact that many details of its edges are missing in the figure. The most interesting thing is that the illusory perceived Necker cube "behaves" in exactly the same way as a real, physical cube, i.e. can spontaneously turn over in the perception of the viewer, consistently addressing him with different facets. This suggests that not only real images, but also illusions can obey the general laws of human perception. If this is the case, then the solution of the question of where we are dealing with images of real objects, and where with illusions, is much more complicated.

In conclusion, we give some examples of even more complex visual illusions. The first one concerns the so-called "impossible" figures, which can be depicted on a plane, but cannot be represented as actually (physically) existing in space.

In figure 2.37, a, b, c, g several types of such figures are shown.

Rice. 237.

Figure 2.37 a is a three-dimensional figure, two parts of which are illusions. It seems to the observer, for example, that in the detail depicted on the right side of Fig. a, there are three rods, although another part of the same figure is shown as if there were only two rods in the same part.

Similarly, the left part of the middle part of the figure, through which three rods pass, is depicted on it as a straight line, standing vertically, and the right part of the same part is shown as unfolded but in relation to it with a straight mind. When perceiving the left side of the corresponding detail, it seems that it is straight, and when moving the view to the right side of the same detail, it seems that it is twisted.

In the part of the figure marked with the letter b, an "impossible" triangle is represented. Looking at any of its angles gives the viewer the impression that the given triangle is straight and, of course, located in the same plane. However, a comparison of the orientations of the planes depicted in the figure shows that they actually form a three-dimensional space. Thus, the illusion is created that the same triangle, which in reality can only be in one plane, is located in space, i.e. in three different planes at once. In addition, this illusion gives rise to a well-known mathematical contradiction, the essence of which lies in the fact that the same plane, "parallel to itself", represents two different, intersecting with each other, i.e. not parallel planes.

The part of the picture marked with a letter in, depicts the same "impossible" triangle, the sides of which consist of cubes oriented in different ways. If in this "triangle" we consider only two sides that form any of its corners, then it seems that they lie in the same plane. However, when taking into account its third side, it seems that this side of the triangle is in a different plane than the first two, and this, as you know, is impossible.

Finally, the part of the figure marked with the letter G, is an "impossible" cube with holes. When considering its two faces: the nearest and the most distant from the observer, one will get the impression that they intersect (see the middle of the figure), which is impossible for a real physical cube, since its opposite faces are parallel and lie in different, non-permanent planes.

The second example of a complex visual illusion refers to the false impression of depth or volume in the perceived image. The corresponding illusion usually appears in the experiment, the scheme of which is shown in Fig. 2.24.

If an image of a rotating wire cube is projected onto a flat screen, which is seen by an observer located behind the screen (Fig. 2.24, a) at then he gets the impression that in front of him is not a wire, but a whole, solid cube, various projections of which are shown in Fig. 2.24, b. In other words, a rotating wire cube casts a flat, two-dimensional projection onto the screen, and the observer seems to see a rotating three-dimensional and, moreover, a complete cube.

Although in this case there is no real change in the illumination of the “faces” of the cube (it is this feature that is used in life to determine the three-dimensionality of a visually perceived object), nevertheless, the observer still sees a three-dimensional cube. It follows that the perception of three-dimensionality is provided by a consistent change in the position in space of the lines that form a three-dimensional object.

Of the complex visual illusions, it is also well known moon illusion. This illusion manifests itself as follows: when the Moon is close to the horizon, it seems to the observer that it is about one and a half times larger in size than when it is at the zenith, although in both cases the images of the Moon on the retina of the eye are the same.

There are several ways to explain the moon illusion, but none of them is completely satisfactory. E. Boring offered the following explanation for this phenomenon. The apparent magnitude of the Moon, according to one hundred opinion, depends on the degree of convergence of the observer's eyes. When the observer sees the Moon near the horizon, his eyes automatically converge, i.e. visual axes of the right and left eyes converge with each other. Since convergence in life usually occurs when the observed object approaches a person, and its apparent size increases in this case, the Moon at the horizon seems to the observer to be larger than at the zenith. When a person raises his eyes to the sky, the visual axes of the right and left eyes, on the contrary, diverge as it happens when looking at a distant object. Accordingly, the receding object for the person observing it decreases in size. Therefore, the Moon at the zenith, according to Boring, seems smaller to the observer than the same Moon at the horizon line.

There is another explanation of the moon illusion, proposed by F. Restle. According to her interpretation, the perceived size of any object, including the Moon, depends not only on the size of its image on the retina, but also on the size of other objects in its immediate vicinity. The smaller these objects, the larger the size of the directly perceived object seems, and vice versa (see, for example, the illusion of perceiving the size of a circle framed by other circles of different sizes in Fig. 2.30, in).

Therefore, if the decision about the size of the Moon is made by the observer on the basis of its comparison with the objects closest to it, then it will seem to him that near the horizon the Moon is larger in size than the same Moon at the zenith, since it is perceived near the horizon against the background of a certain, space-limited landscape and at a small angle of inclination. When the Moon is at its zenith, it is perceived against the background of the vast space surrounding it and therefore seems relatively smaller in comparison with it. However, neither the first nor the second of the above explanations of the moon illusion are recognized by scientists as completely satisfactory, so the question of the causes of this illusion still remains open.

One of the well-known complex visual illusions associated with the perception of space was once demonstrated by A. Ames and was called "Ames room". It manifests itself in the fact that in a specially designed room in which the usual proportions of the room are distorted (the shape of the room is actually not rectangular, and the angles between its walls, floor and ceiling are not straight, although visually this room seems to the observer to be ordinary, rectangular) , people located in the remote corners of a given room seem to a person to be significantly different in height and overall size (see Fig. 2.38).

The illusion of the perceived growth of people, generated by the Ames room, shows that the angle of view of a person determines, in fact, not the visible size of the perceived object, but the ratio of its perceived size to the visually estimated distance.

The well-known illusion associated with the perception of space (depth) is illustrated by phenomenon (illusion) of visual cliff, which is created using the setup shown in Fig. 2.39.

The central launch pad, where the child is at the beginning of the experiment, is shown at the top of the table. It is divided into two

Rice. 2.38.

hollows: opaque, marked with a cellular pattern, and transparent, closed with durable organic glass.

The part of the organic cover that is shaded can conventionally be called a “safe” area, and the visually perceived border between it and the transparent part of the organic sheet creates the illusion of a cliff. Creeping up to it, a child or an animal (experiments were carried out both with people and with animals) sees beyond the line separating the colored

Rice. 239.

and the unpainted part of the table surface, the so-called "visual cliff". Visually, it includes a nearby part of the "safe" site and visible at some distance below, under the "cliff", part of the painted iol. As a result, a picture is formed in the perception of the subject, which usually occurs when a person or animal stands on its edge and looks down when he perceives a really existing cliff. This creates the illusion of a cliff.

Experiments conducted with small children (newborns) and with animals showed that both of them, once at the edge of the "cliff", demonstrate a clearly defined defensive reaction, do not move forward, but, on the contrary, try to move as far as possible, back from the border of the "cliff", go (crawl) to the "safe" part of the launch pad. It clearly follows from this experiment that the perception of space, or at least some of its mechanisms, is genetically incorporated into the development program of many living beings, including humans.

The peculiar forms of the illusion of visual perception are demonstrated by an original experiment organized and conducted by D. Bohm. In this experiment, people with normal vision were asked to wear glasses for some time that distort the space they perceive, including the shape and location of various objects in it. A person who had just put on such glasses at first really perceived the space around him in an illusory, distorted form - exactly as it was optically transformed by the corresponding glasses. However, after some time, the initial distorted perception began to change, and the process of its gradual normalization began, which was expressed in the fact that a person again began to perceive the visually distorted space normally and was well oriented in it.

One possible explanation for this phenomenon is as follows. Over time, existing in a different, visually distorted space, the consciousness (thinking) of a person, apparently, learns not to notice the emerging optical illusions and automatically corrects the perception of the surrounding world in such a way that this world in the eyes of a person looks familiar, without distortion. As a result, after some time, while still wearing glasses that distort space, a person began to perceive it more or less correctly - as if the surrounding space in his perception was not at all optically distorted.

However, when, in the second part of this experiment, the glasses were suddenly removed from the person, his already ordinary vision turned out to be temporarily distorted. True, quite quickly after this, a second normalization of perception took place, and the person returned to his normal vision again.

Normalization of perception and improvement of a person's orientation in space in the experimental situation described above occurred under certain conditions. D. Bohm, discussing the results of the experiment described above, made the following remark in connection with this: “What is interesting in these experiments is that the ability to “relearn” ... depends very much on the ability to actively move your body in space ... Those people who who have the opportunity to walk around the room, are able to quickly adapt their vision to distorting glasses, while people sitting on chairs and passively moving around the same room either do not adapt at all, or such training proceeds much less effectively for them. From these considerations, the following conclusion can be drawn: in order for the perception to be correct, a person needs constant exercises and a continuous influx of information into the central nervous system that corrects the emerging images of perception.

The following experience illustrates the urgent need for this. For experimental purposes, people were immersed in a vessel with water, the temperature of which was very comfortable for them. A person who found himself in the water was unable to see or hear anything for a long time, i.e. was subjected to long-term sensory, visual-auditory deprivation. The special coating that was on his hands did not allow him to receive enough tactile sensations as well. Under these conditions, many subjects showed noticeable deviations in perception, there were visual hallucinations, as well as disturbances in the perception of time. When the period of sensory deprivation ended, the subjects who went through the corresponding experience, in addition, showed a general loss of orientation in space and time. Some people turned out to be incapable immediately after the end of the experiment to correctly perceive and evaluate the shapes of objects. Their perception of color has also changed significantly. D. Bohm draws the following conclusion from these experiments: “The general structural elements of the “superstructure”, established in the brain from early childhood, tend to disintegrate when they do not have to deal with an environment with an appropriate structure.

Let us now turn to a brief analysis of some illusions of motion.

Recall that the previously mentioned illusory movement of the type stroboscopic effect occurs in the observer when, sequentially, with a small interval, two luminous points are lit in front of his eyes, located at a small distance from each other. In this situation, the illusion of "moving" the same point from one place to another may appear. However, it occurs only under certain conditions, for example, when the time interval between two sequentially appearing luminous points is in the range from 30 to 200 ms (milliseconds). If the interval between them is greater than 200 ms, then the corresponding points are perceived as igniting independently of each other (in this case, the illusion of movement such as a stroboscopic effect does not occur). With a very short interval (less than 30 ms), it may seem to the observer that both light sources are ignited almost simultaneously, and the stroboscopic effect type illusion will not arise either.

It has been established that the interstimulus interval of 60 ms is optimal for the appearance of this type of illusion. At an interval of 100 ms, a well-known phi-phenomenon takes place, in which the observer perceives the illusory movement of luminous points.

Among the illusions of movement is also known spinning wheel illusion. It manifests itself in the fact that, according to the spokes of the wheels or along the rims, where individual rotating parts are clearly distinguished, it begins to seem to the observer of this movement, filmed on a movie camera or video camera, that the wheels of a moving machine (car, cart, bicycle, etc.) are rotating in the direction opposite to the movement of the machine itself.

One of the explanations for the illusion of reverse rotation of the wheel is as follows. We are talking about the discrepancy between the number of revolutions of the wheel per second and the number of frames taken by a video camera or a movie camera per second. If the camera shoots 24 frames per second, and the wheel makes 23 revolutions or a multiple of 23 in the same time, then each subsequent frame captures the wheel a little earlier than it has time to complete a full revolution.

During the demonstration of the film to the viewer, accordingly, it begins to seem that the wheel is rolling backwards at a speed equal to one revolution per second. If the speed of rotation of the wheel and the projection of the film on the screen were the same, then the wheels of the car would appear to the observer to be stationary. Finally, if the wheels are spinning at 25 revolutions per second (or any other multiple of 25), assuming the film is projected onto the screen at 24 frames per second, then it will appear to the viewer that they are rolling forward at a speed of one revolution. per second.

There are a lot of illusions of perception of movements, as well as illusions of visual perception. Scientists tried to classify them and present them as typical. One of these classifications includes the following types of illusory perceived movements:

• 1. Alpha movement. This is an apparent movement concerning the apparent, changing size of the perceived object, caused by the successive presentation to the viewer of larger or smaller copies of the corresponding object. In the perception of the viewer, the corresponding object will appear either increasing or decreasing in size.
• 2. Beta movement. It is an illusory movement that occurs during the phi-phenomenon, i.e. movement in the field of view of an actually motionless object from one place to another, generated by successive static representations of this object with small intervals and at an insignificant distance between the locations of these representations in space.
• 3. Gamma movement. This is an illusion of movement, which manifests itself in the expansion or contraction of the visible figure, when its illumination, respectively, either increases or decreases.
• 4. Delta movement. It is a kind of illusory movement in which the apparent location of an object changes along with a change in its illumination.

The presence of visual and other illusions associated with the work of the senses, it would seem, contradicts the fact that human perception is considered a correct reflection of objective reality, since what is manifested in illusions does not correspond to reality. The existence of numerous illusions generated by the work of different analyzers cannot be denied.

However, the presence of illusions is still not a convincing and sufficient proof of the illusory nature of our entire perception as a whole, that it does not correspond to objective reality. In favor of the fact that the perception of a person correctly reflects the objectively existing world, speaks a much larger number of facts than individual phenomena, indicating that our perception can distort reality.

Illusions themselves in most cases have, in addition, a satisfactory explanation, and one of them is the explanation proposed by R. Gregory. In his opinion, illusions arise as a result of deviations from the norm in the work of the senses. For each illusion, in addition, there may be its own, private explanation associated with its specificity. For example, according to I. Rock, many illusions of movement arise due to the fact that human assessments of various movements are relative. They relate to the presence of movement, its absence, speed, trajectory, direction and other parameters of movement, which are usually evaluated relative to any other, stationary or moving objects. When a person is deprived of a certain reference point, or its position in space cannot be firmly established, illusions of movement may arise in a person.

Certain scientific interest for understanding the laws of perception is represented not only by illusions, but also by distortions of perception that occur in certain diseases. It is known, for example, that in a number of diseases there is a characteristic disturbance of perception, called optical agnosia. This is the name given to the inability of a person to recognize familiar objects and phenomena known to him. The term "optical agnosia" was introduced into scientific circulation by 3. Freud in 1891 to refer to an ailment that some of his patients suffered from. It manifested itself in their inability to combine visually perceived elements into a complete, recognizable whole.

People suffering from optical agnosia recognize simple geometric shapes without a heap, but are unable to visually identify complex objects that require the visual system to integrate individual perceptual components into a single, meaningful and recognizable image. Familiar objects that healthy people usually perceive as whole, complete, sick people do not recognize, they perceive as a collection of disparate, unrelated visual elements. Various forms of visual agnosia are known, but in all cases its manifestation is expressed in a violation of the ability to recognize integral objects, despite the continuing ability to recognize individual elements of the same objects.

Of scientific interest is also the so-called prosopagnosia(this term is literally translated into Russian as "without knowledge or recognition of the face"). Patients suffering from this disease, being in other respects absolutely normal people, lose the ability to recognize the faces of people they know and are close to, including relatives. Sometimes they do not even recognize their own faces in photographs or in their mirror image. However, a satisfactory scientific explanation for this phenomenon has not yet been found.

If the images of visual perception related to the perception of objects external to a person show stability or instability depending on the influx of information that confirms or refutes their correctness, then the stability of the images of a person’s internal states associated with his own bodily sensations is probably explained by the constancy of deep processes and mechanisms of the body and the brain. This is evidenced by a phenomenon called limb phantom. It manifests itself in the fact that after the amputation of an arm or leg, a person continues to “feel” the part of the limb missing from him for a long time, and feels it as if it is still in its place, i.e. ns amputated. Sometimes a person even feels pain in it, tries to move it, forgetting that this limb is lost. He, however, from time to time makes attempts to use it to capture or touch visually perceived objects.

In adults, a limb phantom after amputation is almost always observed, and the phenomena associated with it occur, as a rule, only in relation to parts of the body that a person has mastered well enough and constantly used them earlier in practice. A limb phantom in relation to body parts that a person has been missing since birth is not observed. It has also been established that, starting from about 9 years old, amputation of a limb always leads to the appearance of a phantom. This, apparently, is the minimum period during which the human brain, its structures and their connections with sensory processes are formed and fixed.

Characterizing the state of affairs in the field of explaining various visual illusions as a whole, it must be admitted that there is not a single theory that would offer a completely satisfactory, exhaustive and absolutely correct explanation of them. It is quite possible that there is no single process or general mechanism at all (as, indeed, there is no single explanation of the types of perception we have considered), referring to which, we would receive an exhaustive explanation of any of the existing visual illusions.

In this regard, the hypothesis deserves attention, according to which the origin of each individual illusion is almost always associated with several different sources (reasons), some of which are apparently determined by the structure of the visual system, some - by human experience, some - by his attention, memory, imagination. and thinking, as well as actual mental states and other individual characteristics. It has been noticed, moreover, that different people have the same illusions can manifest themselves in different ways.

Summing up the consideration in this paragraph of various illusions of perception, we can state the following.

• 1. Despite the presence of many illusions associated with the work of the senses, a person can navigate in the world around him and have completely objective knowledge about it.
• 2. There are satisfactory explanations for many perceptual illusions, but some of them still do not have such explanations.
• 3. The study of illusions provides a lot of useful information for understanding the general laws and mechanisms of perception.
• 4. There are different explanations of illusions, both general and particular.
• 5. The presence of illusions indicates that, despite the complexity of the structure of the sense organs (analyzers), the subtlety and accuracy of their work, they are not absolutely perfect devices for objective and unmistakable knowledge of the surrounding reality by a person.
• 6. The existence of illusions of perception is not proof of the unreality of a person's picture of the world, and overcoming illusions is direct evidence that a person nevertheless correctly perceives the world around him.
• 7. Finding answers to questions related to the illusions of perception will make it possible to make significant progress in the knowledge of the mechanisms and patterns of a person's perception of himself and the world around him.

• The name "optical illusions" is accepted in some sciences, for example, physics, but from a psychological point of view, it is not entirely accurate. It indicates that the cause of such an illusion lies in the optics of the eye, while this illusion may be associated not with the optical device of the eye, but with the processes occurring in the central nervous system.
• This experience and its results are a strong argument in favor of the fact that the illusions of perception, even if they arise, do not prevent a person from correctly perceiving the world around him and orienting himself in it.
• Bohm D. The role of invariants in perception // Reader on sensation and perception. M., 1975. S. 174.
• There. pp. 177-178.

Illusions of perception

The word "illusion" comes from the Latin word illudo, meaning "I deceive, mock, play." Indeed, since ancient times, the property of our psyche is often known to perceive the external world distortedly. Separate examples of illusory perception can already be found among ancient authors: in the scientific treatises of the Greek philosopher Aristotle, the Roman architect Vituvius. The poet and philosopher Titus Lucretius Car, noting the relativity of our visual perception, wrote:

“Our eyes cannot perceive the nature of objects. Therefore, do not impose on them delusion of reason.

Many unresolved problems are fraught with our psyche. And perhaps, the more we learn about it, the more amazing mysteries it poses to the scientist. This is one of these mysteries and are the so-called deceptions of the senses or illusions of perception. It seems to me that this already well-known property of the psyche plays a far from secondary role in our daily life, and for an inquisitive mind it is another reason to ponder the age-old question: how do we perceive the world around us?

We still know little about the nature of illusions, and no one will undertake to fully answer this question today. The most studied to date are visual (or optical) illusions, which are errors in estimating and comparing the lengths of segments, angles, distances between objects, in the perception of the shape of an object, etc. Errors in our judgments about the visually perceived world are connected in largely due to the fact that the created images, thanks to the active work of the brain, are holistic (integrative), and therefore the assessment of the subject as a whole is transferred to the assessment of its details. Moreover, it is interesting to note that the more integral the image, the stronger the illusion of evaluating its individual parts. So, in the figure, the diagonal AE a large parallelogram appears to be longer than the diagonal ED smaller, in fact, their lengths are equal. Visual illusions also arise as a result of the ability of the eye to overestimate the length of vertical lines compared to horizontal ones. If you want to see this, take a look at the picture (the height of the hat seems to be greater than the width of its brim).

Another group of visual illusions arises due to the property of our perception to evaluate an object, taking into account everything that surrounds it. Let's consider a circle surrounded by eight small circles. When compared with another circle placed between five large circles, it seems larger. The psychological law of contrast is at work here. Measure and you will see that the circles are exactly the same size. We have to admit the unreliability of visual perception. However, we must not forget that the final result of recognizing an object largely depends on our past life experience, i.e., memory, which stores countless visual images along with their meaning and significance for our behavior.

Illusory deceptions are of great importance in the visual arts and architecture, where their skillful use expands the possibilities of the artist or architect. Probably, many of you are familiar with the laws of perspective that are used when creating works of art. Those who were lucky enough to visit the palace of the city of Pavlovsk (near St. Petersburg) could see the ceiling painting of one of the halls, commissioned by the unsurpassed master of perspective painting of the 18th century, the talented Italian artist Pietro Gonzago. We even forget that there is a flat surface of the ceiling above us, this complete illusion of space going up is so strong.

But look at the drawing, also built taking into account the laws of perspective: the height of a tree, a house, and any other object is perceived to be smaller than it really is. Our practical experience has taught us to make appropriate corrections for such a distorted perception, and we correctly represent the relative sizes of the depicted objects.

Often we ourselves actively use the effect of visual illusion in our daily life. For example, when choosing clothes, knowing certain rules helps us hide some body defects. So, a short young man or girl, trying to look taller, should remember that a vertical striped fabric visually lengthens the figure; the same effect is achieved by including lines of the longitudinal direction in the style of clothing. And vice versa: the predominance of horizontal stripes and lines in clothes will make a tall and thin figure more proportional. We see that in all these cases, it is as if the opposite effect occurs: individual details of the image (vertical or horizontal stripes on clothes) change the assessment of the most integral image.

When perceiving this picture, the laws of perspective apply.Depending on what our attention is directed to, we see in one picture either a young woman or an old woman.

It is interesting to note that visual illusions are closely related to the direction of our attention. Indeed, in order to see some object from the many others located around, we must fix our attention on this object. Looking closely at one subject, we may for some time not pay attention to all the others. This means that our perception is selective, and we do not just passively and indifferently “photograph” what is in front of us, but we choose with interest what is most important and significant for us at the moment. When looking at one drawing, one can alternately see either a young woman in a somewhat old-fashioned hat with feathers, or an old woman with a fur collar, with a prominent chin and a large hooked nose. It all depends on what it's aimed at. Attention, in the ear of a young woman or in the eye of an old woman.

Non-existent figure

Finally, another type of visual illusion consists in the complete contradiction of our sensory sensations and reasonable interpretations of the subject. This page depicts an object that does not exist in nature. The left side is perceived as a composition of round rods arranged in parallel. And the right half is seen as a tetrahedral double angle. In the middle of the drawing, we find a transition area in which we are trying to transfer one view to another part of the drawing. However, we are not able to accurately mark this transition. Cover the left side of the picture first with your hand, and then the right side, and you will see two completely different images. Thus, reason, as a result of the ability to think logically, contradicts visual perception and experience.

All of the above indicates that our perceptions are only the first stage of cognition, the initial stage of acquaintance with the subject, which is assessed not in isolation, but in the context of the entire environment. Perception is deepened by thinking and tested by practice.

Illusions are not an accident So, we looked at two variants of the development of an illusion taken at random. We have seen how the love illusion arises and how the illusion of danger (threat) develops. But we admit to ourselves that only with a big stretch can we call the feeling described above

Illusions Children's illusions are most often associated with rewards and punishments. The good is rewarded, the bad is punished. Small children usually have some kind of Santa Claus who "monitors" their behavior and takes everything into account. But only babies have it. Older kids into it