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Whole and part. Encyclopedia of visual illusions

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Very many erroneous visual impressions are due to the fact that we perceive the figures we see and their parts not separately, but always in some relation with other figures surrounding them, some background or setting. This section includes, perhaps, the largest number of visual illusions encountered in practice. All these illusions can be divided into five groups.

First, when comparing two figures, of which one is really smaller than the other, we mistakenly perceive all parts of the smaller figure as smaller, and all parts of the larger figure as large ("the whole is more - more and its parts"). Under these conditions, the error appears not due to defects in the eye as an optical device, but rather due to the psychophysiological stage of visual perception (Fig. 21-28).

We mistakenly transfer the properties of a figure to its parts. A. L. Yarbus indicates the general reason for the appearance of illusions (Fig. 21-27), which consists, as it were, in the “tendency” to determine the distances not between the edges of objects, but between the objects themselves. This is evidenced by the illusions observed in Fig. 28, where those distances that should be determined in relation to the edges of the black circles are perceived as increased or decreased, and our vision relates them to the centers of the circles.

Rice. 21. The right figures are larger than the left ones (the figures as a whole), however, parts of these figures can be equal to parts of the left figures, although they seem to be much larger

Rice. 22. The portions of the vertical centerlines between the lowest and middle points appear larger than the portions of the centerlines between the middle and highest points.

Rice. 23. AB = BC. The axial lines of the lower figures are equal in length

Rice. 24. ab seems to be less than ef, and ef seems to be less than cd; in fact, all three segments are equal to each other

In figure 25, the distance ab seems to be greater than cd; actually ab=cd

In figure 26, the distance ab seems to be greater than cd; actually ab=cd

In figure 27, the distance ab seems to be greater than cd; actually ab=cd

Rice. 28. The distances between two vertical lines and between a vertical line and one circle on the left side of the figure do not seem to be equal to the distances between two circles on the right side of the figure. In fact, these distances are equal to each other (drawing by A. L. Yarbus)

Secondly, there are cases of illusions of the same kind, with the only difference that the judgment about the visual image goes in the opposite direction: not from the "whole" to the "part", but from the "part" to the "whole". Examples of such illusions are shown in fig. 29-32. A similar error of vision also occurs when we consider separately a coin worth two kopecks and a number on the state treasury note of the USSR worth 1 ruble. It seems to us that the coin will not cover this number, although it certainly covers it from the first to the last digit.

Rice. 29. The angle contracted by an arc on the right seems to be larger than the angle contracted by the arc on the left. They are in fact equal.

Rice. 30. The upper figure on the perimeter and area does not seem to be equal to the lower one; in fact, when superimposed, the shapes will be combined

Rice. 31. Less clearly observed inequality of two equal figures

Rice. 32. The diameter of the circle seems to be greater than the segments AC and BD; in fact he is equal to them

Thirdly, when perceiving figures as a whole and their individual parts (lines, angles, individual details), visual illusions can occur due to the general psychological law of contrast, that is, the situation, the environment of these parts and their relationship with other parts of the figure. Examples can be found in Fig. 33-34. Here we are not talking about the contrast of brightness or color contrast, which is practically negligible or absent here.

Rice. 33. The inner acute angle of the right figure seems to be smaller than the inner acute angle of the left. They are in fact equal.

Rice. 34. The inner circle on the left seems larger than the right inner circle.

Rice. 35. The same effect as in fig. 34

Rice. 36. The circle adjoining closer to the sides of the acute angle on the left seems to be larger than the circle on the right.

Rice. 37. The deck of the right sailboat seems to be shorter than the deck of the left steamer

Rice. 38. The distance between points closer to the apex of an acute angle seems to be greater than the distance between points more distant from the apex. The illusion completely disappears if you look at the drawing from the side of the top of the corner so that the eye slides along the plane of the drawing.

Rice. 39. The right arc seems to be shorter and more curvature than the left

Rice. 40. The heights of the triangles are halved, but it seems that the parts adjacent to the top are shorter

Rice. 41. The upper inner oval seems to be smaller than the lower one, but in reality they are equal

Rice. 42. The sides of a triangle seem to be smaller than the sides of a square, and the sides of a square are smaller than the sides of a pentahedron. All these segments, however, are equal. The illusion is created solely due to the increase in the perimeters and areas of these figures.

Rice. 43. The base of the figure a seems to be smaller than the base of the figure b, the diameter of the circle a`a` seems to be less than the distance b`b` although all these lines are equal to each other

Rice. 44. Each left figure seems to be larger than each right one, although all the figures are the same. The illusion will disappear if you look at this drawing from the right side so that the eye slides along the plane of the drawing.

Fourthly, illusions are known, the cause of which lies in the assimilation (assimilation) of one part of the figure to another. Several such illusions are shown in Fig. 45-48.

Rice. 45. The direct tangent to all circles of different radii seems to be a curve, since we involuntarily liken it to the upper curvilinear boundary. (Illusion by S. Thompson.)

Rice. 46. ​​The single helix shown on the left does not give the impression that the helix is ​​moving towards a vanishing point with other similar helixes. The same spiral shown on the right gives the impression

Rice. 47. The arrangement of segments of concentric circles with thickenings at the ends, according to the principle of declining them towards a spiral, gives the impression that the figure shows white spirals on a black background.

Rice. 48. Due to the spiral shading of the gray background, white lines interrupted in places appear to be spirals; in fact, they are concentric circles, which is easy to verify with a compass or pencil

If, for example, Fig. 47 and 48 illuminate for a moment with a spark flash, then the illusion (at least for a certain duration of the flash) will disappear. During the flash, the eye does not have time to move noticeably, following the spirals of the background and likening light circles to these spirals. In this case, the situation or background, as it were, disappears.

The eye has quite distinct vision only in the region of the central depression of the macula, i.e., in a very small area of ​​the retina. Fixing, for example, some word on a printed page, we can hardly read the next word, and then we can’t make out anything at all (if our eyes are motionless). Therefore, vision is, in essence, viewing. Our gaze is constantly moving. This sometimes gives rise to illusions similar to those shown in Fig. 49 and 50.

Rice. 49. The sides of the square, depicted by broken lines against a background of alternating white, gray and black circles, seem to be strongly displaced and do not belong to the square.

Rice. 50. The letters appear to be slanted but are actually vertical to the horizontal lines of the picture frame.

Finally, one should point to the last group of illusions associated with the visual perception of the whole and the part, the cause of which lies in the inability of the visual apparatus to sometimes distinguish a part from the whole due to the complexity of the situation.

For example, in the left figures of Fig. 51 and 52, we find it difficult to immediately identify the squares, although they are there (in the right figures they are highlighted with thicker lines).

Rice. 51. A square is depicted, but it is masked by the lines surrounding it and is not clearly visible, on the right it is isolated from the situation

Rice. 52. A square is depicted, but it is masked by the lines surrounding it and is not clearly visible, on the right it is isolated from the situation

Note that the selected square in Fig. 52 appears to be elongated in the horizontal direction, which is explained by the ability of our vision to overestimate (exaggerate) sharp corners.

Numerous illusions in this section tell us that here most often an inaccurate, distorted impression is created as a result of an incorrect judgment about the visible, and it is not the eye that is mistaken, but the brain uncertainly explains to us the impressions of the external world.

Indeed, we have no reason to believe that the optical images of the figures in Figures 21-52 on the retina of our eye will be incorrect. Consequently, these illusions are created not as a result of optical shortcomings of the eye, but as a result of certain rules for viewing the picture (movement of the eyes, position of the picture) and some laws of the work of the retina and the brain that are unconscious to us and still unknown to us, connecting individual irritating impulses into the overall picture. In the illusions presented in this section, we can trace the dialectical unity of analysis and synthesis, i.e., the connection of parts with the whole, when in the parts we observe the properties of the whole, while the properties of the parts affect the whole.

Author: Artamonov I.D.

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