There is also the phenomenon of synesthesia (color hearing), when two sensory systems of sight and hearing are connected and influence each other in the final perception. A person with color hearing, when listening to music, sees color visual images. Such people are called synesthetics; they can read plain text without any problems, although each letter (sound) has a different color for them. When they are presented with a text of multicolored letters, they feel uncomfortable, they begin to stumble, the speed of reading slows down. For them, the randomly given color of the letter does not coincide with their perception of the color of the letter. In the history of music many famous Russian composers were synesthetics, including A.N. Scriabin and N.A. Rimsky-Korsakov. Frenchman O. Messiaen and Lithuanian musician and artist M.K. Churlionis were also synesthetics.
Figure 1.3.23 The task for the Stroop effect.
1.4 Space Perception
1.4.1 Monocular Spatial Signs
The retina is a two-dimensional curved surface. Despite this, we can estimate the distance of objects in the three-dimensional world. The distance of objects is determined on the basis of some monocular and binocular signs. Spatial signs that are perceived by one eye are called monocular (or pictoral). Monocular spatial signs are mostly static, i.e., when the observer and objects of the field of view are fixed [Gippenreiter, 2002], [Shiffman, 2008], [Abbasov, 2016]. The perception of still scenes, photographs, art paintings is based on static monocular signs. Monocular signs convey the depth of space and distance by visual means, and the observer has an illusion of volume when viewing pictures.
Size of objects. The first monocular feature is the relative size of objects; a smaller object is perceived as more distant.
Interposition. Partial blocking or overlapping of one object by another is called interposition. The object located closer may overlap the objects located behind (Figure 1.4.1). Interposition to determine the relative distance of objects.
Figure 1.4.1 Flat and three-dimensional interposition of one scene.
Aerial perspective. When viewing the surrounding landscapes of objects nearby, we see more clearly than distant objects. This monocular source of information is called the air perspective; it arises due to the scattering of light on the smallest particles of the surface layer of the atmosphere.
Shadow and Luminosity. Close to the light source surfaces of objects have the greatest luminosity. With distance from the light source, the luminosity of the surfaces decreases and their shading increases. The shadow that falls on the surface of the object itself, blocking the light, is called its own. If the shadow of an object falls on another surface, it is called a falling one. These shadows are important signs of the depth of the scene; they tell us information about the shape of objects, the distance between them and the location of the light source.
The work of [Gonzalez, Niechwiej-Szwedo, 2016] describes the influence of monocular vision on the accuracy of coordination of hand movements at the moment of capture. It’s known that the moveable eyes are in motion up to the completion of the movement. The eyes moving to object is analyzed in the space and recognized thus simplifying the control of subsequent movements. However, the monocular vision doesn’t allow the complete determination of the position of the object and hands in the space. Fifteen people who carry out the control action using the video tracker and system of motion capture took part in the experiment. As a result the time for taking the bead and pulling it on the needle at the monocular vision was increased up to 2.5 sec, and in case of binocular vision it was 2 sec. The obtained results prove the defining role of binocular vision in the everyday living of man.
The work of [Luke, Henderson, 2016] considers the influence of significance of visual stimulus content on eye movement. The text, photos of townscapes, landscape pictures and their analogs such as stylized pseudo stimuli were used as the visual stimuli. As a result it was determined that the duration of fixation and saccades amplitude were larger for pseudo stimuli as they need more time to be recognized and perceived.
Linear perspective. In the perception of the depth of space, linear perspective plays an important role. Linear perspective provides for a gradual decrease in the magnitude of distant objects and distances between them. The most obvious example of a linear perspective is railroad rails (Figure 1.4.2) [Website istockphoto, 2020]. Despite the parallelism, it seems that the rails in the distance converge at a point called the vanishing point.
Figure 1.4.2 Linear perspective.
1.4.2 Monocular Motion Parallax
Monocular motion parallax (from the Greek word paralaxis – change) is a monocular source of information about the depth and relative position of objects in view, resulting from the movement of an observer or objects. When the observer fixes his gaze on some point of the field of view, and at this time he moves, it begins to seem to him that objects lying closer to the fixation point move faster than more distant objects. During the movement of the head, the images of objects in remote locations on the retina will be mixed at different distances. It seems to the observer that more closely spaced objects move in the direction opposite to the direction of eye movement, and more distant objects move in the same direction [Shiffman, 2008], [Abbasov, 2019].
1.4.3 Binocular Signs
For the perception of primary visual information, monocular signs of space play an important role. However, to accurately determine the depth of space requires the activity of both eyes. Binocular signs are spatial information that can only be obtained by perceiving the surroundings with both eyes.
Binocular disparity. Animals with a frontal arrangement of eyes (predators, primates) see a large part of the visual field with both eyes. Within the area of binocular overlap, two eyes receive slightly different images of the same three-dimensional visual information. The field of view of one eye is somewhat different from the field of view of the other. This difference between the two retinal images is called binocular disparity (binocular parallax). Disparity is strongly pronounced for closely located objects, and decreases as they are removed. After four meters, the difference between retinal images becomes insignificant, and binocular disparity weakens.
1.4.4 Binocular Disparity and Stereopsis
Due to the binocular disparity of the images on the retina of both eyes, there arises a special perception of the depth of space and volume, which is called stereoscopic vision, or stereopsis (from the Greek Stereos – volumetric and opsis – vision) [Luria, 2006], [Shiffman, 2008], [Abbasov, 2016]. One of the most impressive examples of stereoscopic vision is the perception