The sensitivity of the analyzer changes under the influence of the adaptation of the sensory organ to the current stimulus. This phenomenon is called adaptation. Adaptation can occur both in the direction of increasing sensitivity (when there is a transition from strong stimuli to weak ones) and in the direction of reducing it (when there is a transition from weak stimuli to strong stimuli).
Adaptation manifests itself in all types of sensations. It is especially strong in the areas of vision, smell, skin sensations and taste; less pronounced in the hearing area. Adaptation of all sense organs proceeds according to similar patterns, and since adaptation of vision to darkness and light has been especially studied, consideration of visual adaptation can reveal general laws adaptation. may feel hot at first, but gradually the thermal sensation weakens. However, strong heat and cold stimuli do not provide adaptation or it proceeds very slowly.
In the area of smell, the process of adaptation proceeds differently to different odors. Thus, the smell of camphor ceases to be felt after 1-2 minutes, which indicates a strong decrease in sensitivity. However, adaptation to odors that include painful irritation (mustard, ammonia) occurs slowly, and if the irritant is strong enough, it does not occur at all, and the irritant causes intolerance. unpleasant feeling. Adaptation to odors, like adaptation to sounds, is selective: when sensitivity to one odor decreases, sensitivity to other odors may not decrease, although adaptation extends to a group of similar odors.
Adaptation to painful irritations is weakly expressed. Very severe pain does not allow adaptation at all. This is explained biological role pain as a signal of disturbance normal condition body.
It is necessary to distinguish the phenomenon from adaptation sensitization. While adaptation is an increase in sensitivity (in some cases), and a decrease in it (in other cases), and at the same time is an adaptation of an organ to the stimulus acting on it, sensitization is always an increase in sensitivity and is caused by reasons other than adaptation . A significant role among them is played by the interaction of analyzers. Under certain conditions, it entails an increase in the sensitivity of one of the senses under the influence of the simultaneous functioning of the other. This phenomenon is well demonstrated by the experience of P.P. Lazarev, which he performed in a wide audience. In the room where the experiments took place, a quiet tone of equal intensity sounded. When the lights were turned on and off rhythmically, the sound seemed to vibrate, changing its intensity. This change in the sensation of sound occurred due to the fact that when exposed to light, the sensitivity of the hearing organ increased and the sound was perceived louder.
Similar facts were observed in the studies of Kravkov, Kekcheev, Schwartz and others. It has been found, for example, that light muscle work, wiping the face cold water, weak sound side stimuli increase the sensitivity of vision (strong side stimuli, on the contrary, due to negative induction, reduce it).
A sensitizing effect can be exerted not only by simultaneous stimulation of another sense organ, but also by simultaneous stimulation of other parts of the same sense organ. The sensitivity of some parts of the retina, for example, as shown by Teplov’s experiments, increases if at the same time moderate light is applied to other parts of the retina of the same eye (strong side irritation of the same sense organ causes, this time due to negative induction, a decrease in sensitivity).
Sensitization sensory organs can also be caused by the action of certain pharmacological substances.
Adaptation called a decrease or increase in the sensitivity of analyzers as a result of continuous or prolonged exposure to stimuli. Thanks to adaptation, the sensations that were sharp and strong during the initial stimulation of the receptor, then when continuous action the same irritation weakens and may even disappear completely. An example is adaptation to long-lasting odors. In other cases, adaptation is expressed, on the contrary, in increased sensitivity. For example, when moving from light to darkness, we do not distinguish objects around us. However, after some time, this feeling becomes possible.
Sensitization is called an increase in the sensitivity of analyzers due to an increase in the excitability of the cerebral cortex under the influence of certain stimuli. For example, taking caffeine or any other stimulant increases nervous activity cortex, and therefore the sensitivity of the analyzers increases: auditory, visual, tactile and other sensations begin to flow more clearly than in normal conditions.
The sensitivity of some analyzers may increase under the influence of the simultaneous activity of other analyzers. For example, when the eye is irritated by light of optimal intensity, at which visual function is carried out easily and quickly, sensitivity to sounds also increases; visual acuity and color sensitivity increase with simultaneous prolonged exposure to moderate sounds, sensations of cold increase auditory and visual sensitivity; on the contrary, hot temperatures and stuffy atmosphere lead to their decrease (S.V. Kravkov). Rhythmic auditory sensations help enhance muscle-motor sensitivity: we feel and perform our movements better if physical exercise is accompanied by music.
Physiological basis Sensitization of sensations is the process of interconnection of analyzers. The cortical parts of some analyzers are not isolated from others; they take part in the general activity of the brain. In this regard, the movement nervous processes in the central sections of some analyzers, according to the laws of irradiation and mutual induction, is reflected in the activities of other analyzers.
This relationship is strengthened when the functions of different analyzers participate in some common activity. For example, the muscular-motor and auditory analyzers can be organically connected with the execution of movements (the nature of the sound corresponds to the nature of the movements), and then one of them increases the sensitivity of the other.
The sensitivity of analyzers sometimes increases also due to the fact that they for a long time were not affected by the corresponding stimuli. For example, the sensitivity of the eye to light after 30-40 minutes in the dark can increase 20,000 times.
13. Interaction of sensations and synesthesia
The individual senses we have just described do not always work in isolation. They can interact with each other, and this interaction can take two forms.
On the one side, individual sensations can influence each other Moreover, the work of one sense organ can stimulate or inhibit the work of another sense organ. On the other hand, there are deeper forms of interaction in which the senses work together causing a new, maternal type of sensitivity, which in psychology is called synesthesia.
Let us dwell separately on each of these forms of interaction. Research conducted by psychologists (in particular, the Soviet psychologist S. V. Kravkov), showed that the work of one sense organ does not remain without influence on the work of other sense organs.
Thus, it turned out that sound stimulation (for example, a whistle) can sharpen the functioning of the visual sense, increasing its sensitivity to light stimuli. Some odors also influence in the same way, increasing or decreasing light and auditory sensitivity. A similar influence of some sensations on other sensations apparently occurs at the level upper sections trunk and optic thalamus, where the fibers conducting excitations from various organs feelings come closer and the transfer of excitations from one system to another can be carried out especially successfully. The phenomena of mutual stimulation and mutual inhibition of the functioning of the sense organs are of great practical interest in situations where there is a need to artificially stimulate or suppress their sensitivity (for example, during a flight at dusk in the absence of automatic control).
Another form of interaction between the senses is their joint work, in which the qualities of one type of sensation (for example, auditory) are transferred to another type of sensation (for example, visual). This phenomenon of transferring the qualities of one modality to another is called synesthesia.
Psychology is well aware of the facts of “colored hearing,” which is activated in many people and is especially clearly manifested in some musicians (for example, Scriabin). Thus, it is widely known that we evaluate high sounds as “light” and low sounds as “dark”. The same applies to odors: it is known that some odors are rated as “light” and others as “dark”.
These facts are not random or subjective; their pattern was shown by a German psychologist Hornbostel, who presented subjects with a series of odors and asked them to correlate them with a series of tones and with a series of light shades. The results showed great consistency, and, most interestingly, the odors of substances whose molecules included larger number carbon atoms were correlated with darker shades, and the odors of substances whose molecules included few carbon atoms were correlated with light shades. This shows that synesthesia is based on objective (not yet sufficiently studied) properties of agents affecting humans.
It is characteristic that the phenomenon of synesthesia is not distributed equally in all people. It is especially clearly manifested in people with increased excitability of subcortical formations. It is known to predominate in hysteria, can increase markedly during pregnancy, and can be artificially induced through the use of a number of pharmacological substances (for example mescaline).
In some cases, the phenomena of synesthesia manifest themselves with exceptional distinctness. One of the subjects with exceptional severity of synesthesia, the famous mnemonist Sh., was studied in detail by Soviet psychology. This person perceived the weight of voices as colored and often said that the voice of the person addressing him was “yellow and crumbly.” The tones he heard gave him visual sensations of various shades (from bright yellow to dark silver or purple). The perceived colors were felt by him as “ringing” or “dull”, “salty” or crunchy.” Similar phenomena in more erased forms they occur quite often in the form of an immediate tendency to “color” numbers, days of the week, names of months in different colors.
The phenomenon of synesthesia is of great interest for psychopathology, where its assessment can acquire diagnostic value.
The described forms of interaction of sensations are the most elementary and, apparently, occur primarily at the level of the upper trunk and subcortical formations. There are, however, also more complex forms of interaction between the senses or, as I.P. Pavlov called them, analyzers. It is known that we almost never perceive tactile, visual and auditory stimuli in isolation: when perceiving objects of the external world, we see them with the eye, feel them by touch, sometimes perceive their smell, sound, etc. Naturally, this requires the interaction of the senses (or analyzers) and is ensured by their synthetic work. This synthetic work of the sense organs occurs with the close participation of the cerebral cortex and, first of all, those “tertiary” zones (“overlap zones”) in which neurons belonging to different modalities are represented. These “overlap zones” (we talked about them above) provide the most complex shapes collaboration analyzers underlying objective perception. TO psychological analysis We will discuss the main forms of their work below.
State educational and pedagogical Publishing house of the Ministry of Education of the RSFSR, M., 1955.
With continuous and prolonged exposure to any stimulus, the corresponding receptors adapt to it, as a result of which the intensity begins to decrease nervous excitement, transmitted from receptors to the cortex, which underlies the so-called adaptation.
Thanks to adaptation, sensations that were sharp and strong during the initial irritation of the receptor, then, with the continuous action of the same irritation, weaken and may even disappear completely. An example is adaptation to a long-lasting odor. In some cases, adaptation is expressed, on the contrary, in increased sensitivity. For example, when moving from light to darkness, we do not distinguish objects around us. However, after some time, this feeling becomes possible.
Sensitization is an increase in the sensitivity of analyzers. It is often associated with general increase excitability of the cerebral cortex under the influence of certain stimuli. For example, taking caffeine or any other stimulants enhances the nervous activity of the cortex, and therefore the sensitivity of the analyzers increases: auditory, visual, tactile and other sensations begin to flow more clearly and distinctly than under normal conditions.
Of great interest is the type of sensitization, which consists in increasing the sensitivity of some analyzers under the influence of the simultaneous activity of other analyzers. For example, when the eye is irritated by light of optimal intensity, at which visual function is carried out easily and quickly, sensitivity to sounds also increases. Conversely, visual acuity and color sensitivity increase with simultaneous prolonged exposure to moderate-intensity sounds.
Can play the same role taste sensations: certain doses of sugar increase the sensitivity of the visual analyzer; moderate sensations of cold increase auditory and visual sensitivity. On the contrary, hot temperatures and stuffy atmosphere lead to their decrease.
Rhythmic auditory sensations help enhance muscle-motor sensitivity: we feel and perform our movements better if physical exercise accompanied by music.
The physical basis for the sensitization of sensations is the processes of interconnection of analyzers, which are in constant interaction. The cortical parts of some analyzers are not isolated from others; they take part in the general activity of the brain. In this regard, the movement of nervous processes in the central sections of some analyzers according to the laws of irradiation and mutual induction is reflected in the activity of other analyzers.
This relationship is strengthened when the functions of different analyzers participate in some common activity. For example, the muscular-motor and auditory analyzers can be organically connected with the execution of movements (the nature of the sound corresponds to the nature of the movements), and then one of them increases the sensitivity of the other.
The interaction of analyzers, leading to the sensitization of some sensations by others, can also be observed when the analyzers are not connected general activities(sugar and increased visual threshold; cold and increased hearing acuity). In these cases, the phenomena of sensitization are explained by the establishment of temporary conditioned reflex connections between analyzers; as a result of this, which arose according to the laws of education conditioned reflexes, communication, an increase in the activity of one analyzer is a natural condition for an increase in the activity of another analyzer.
For example, a cold stimulus not only excites the temperature analyzer, but also (through the latter) communicates with the auditory analyzer.
The sensitivity of analyzers sometimes also increases due to the fact that they have not been exposed to appropriate stimuli for a long time. For example, the sensitivity of the eye to light after 30-40 minutes in the dark can increase 20,000 times.
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7. Sense organs are the only channels through which external world penetrates into human consciousness. They give a person the opportunity to navigate the world around him. If a person were to lose all his senses, he would not know what was happening around him, would not be able to communicate with people around him, find food, or avoid dangers. The sense organs receive, select, accumulate information and transmit it to the brain, which every second receives and processes this huge and inexhaustible flow. The result is an adequate reflection of the surrounding world and the state of the organism itself. And all this is extremely hard work, consisting of many thousands of operations per second, is performed continuously.
8. A person constantly needs to receive information about the world around him. Adaptation of the organism to the environment, understood in its very in a broad sense This word presupposes a constantly existing information balance between the environment and the organism. Information balance is opposed by information overload and information underload (sensory isolation), which lead to serious functional disorders body.
9. Sense organs are, in fact, energy filters through which corresponding changes in the environment pass. By what principle is selection carried out? useful information in sensations? Several hypotheses have been formulated.
10. According to the first hypothesis, there are mechanisms for detecting and passing limited classes of signals, and messages that do not correspond to these classes are rejected. The task of such selection is performed by comparison mechanisms.
11. The second hypothesis suggests that the acceptance or non-acceptance of messages can be regulated on the basis of special criteria, which, in particular, represent the needs of a living being. All animals are usually surrounded by a sea of stimuli to which they are sensitive. However, most living organisms respond only to those stimuli that are directly related to the needs of the organism.
12. According to the third hypothesis, the selection of information in sensations occurs on the basis of the criterion of novelty. Indeed, in the work of all sense organs there is an orientation toward changing stimuli. Under the influence of a constant stimulus, sensitivity seems to dull and signals from the receptors stop entering the central nervous system. Thus, the sensation of touch tends to fade. It can completely disappear if the irritant suddenly stops moving across the skin. Sensory nerve endings signal the brain about the presence of irritation only when the strength of the irritation changes, even if the time during which it presses harder or less on the skin is very short. The visual and auditory analyzers are also characterized by the extinction of the indicative reaction to a constant stimulus.
13. During educational activities changes occur in the processes of mental perception (perception), such as sensory adaptation and sensitization.
14. The sensitivity of analyzers, determined by the value of absolute thresholds, is not constant and changes under the influence of a number of physiological and psychological conditions, among which special place occupies the phenomenon adaptation.
15. Adaptive regulation of the level of sensitivity, depending on what stimuli (weak or strong) affects the receptors, has a huge biological significance. Adaptation helps the sensory organs to detect weak stimuli and protects the sensory organs from excessive irritation in the event of unusually strong influences.
16. The phenomenon of adaptation can be explained by those peripheral changes that occur in the functioning of the receptor when prolonged exposure an irritant on him. Thus, it is known that under the influence of light, the visual purple located in the rods of the retina decomposes (fades). In the dark, on the contrary, visual purple is restored, which leads to increased sensitivity. In relation to other sense organs, it has not yet been proven that their receptor apparatus contains any substances that chemically decompose when exposed to a stimulus and are restored in the absence of such exposure.
17. The phenomenon of adaptation is also explained by the processes occurring in the central sections of the analyzers. With prolonged stimulation, the cerebral cortex responds with internal protective inhibition, reducing sensitivity. The development of inhibition causes increased excitation of other foci, which contributes to an increase in sensitivity in new conditions (the phenomenon of sequential mutual induction).
18. Increased sensitivity as a result of the interaction of analyzers and exercise is called sensitization.
19. Physiological mechanism the interactions of sensations are the processes of irradiation and concentration of excitation in the cerebral cortex, where the central sections of the analyzers are represented. According to I.P. Pavlova, a weak stimulus causes in the cortex cerebral hemispheres a process of excitation that easily radiates (spreads). As a result of the irradiation of the excitation process, the sensitivity of the other analyzer increases. When exposed to a strong stimulus, a process of excitation occurs, which, on the contrary, tends to concentrate. According to the law of mutual induction, this leads to inhibition in the central sections of other analyzers and a decrease in the sensitivity of the latter.
20. A.R. Luria identified two types of sensitization. The first type is long-term, permanent, depends on sustainable change occurring in the body. Sensitivity acuity increases with age, reaches a maximum at 20-30 years, then gradually decreases. The second type is temporary in nature, depending on both physiological and psychological emergency effects on the subject’s condition.
21. A change in the sensitivity of analyzers can be caused by exposure to secondary signal stimuli (speech).
22. Knowing the patterns of changes in the sensitivity of the sensory organs, it is possible, by using specially selected side stimuli, to sensitize one or another receptor, i.e. increase its sensitivity.
23. Sensitization can also be achieved as a result of exercise. It is known, for example, how pitch hearing develops in children involved in music. The possibilities for training the senses and improving them are very great. There are two areas that determine increased sensitivity of the senses:
24. 1) sensitization, which spontaneously results from the need to compensate for sensory defects (blindness, deafness);
25. 2) sensitization caused by the activity, specific requirements of the subject’s profession.
It would be wrong to think that both the absolute and relative sensitivity of our sense organs remains unchanged and that its thresholds are expressed in constant numbers.
As studies have shown, the sensitivity of our senses can change, and within very wide limits. This variability in sensitivity depends on both conditions external environment, and from a number of internal (physiological and psychological) conditions, chemical influences, subject's attitudes, etc.
Distinguish two main forms of sensitivity change, of which one depends on environmental conditions and is called adaptation, and the other depends on the conditions of the body and is called sensitization.
Let us dwell separately on each form of change in sensitivity.
1. Adaptation. It is known that in the dark our vision becomes sharper, and in strong light its sensitivity decreases. This can be observed when you move from a dark room to light or from a brightly lit room to a dark one. In the first case, a person’s eyes begin to experience pain, the person temporarily “goes blind,” and it takes some time for the eyes to adapt to the bright light. In the second case, the opposite phenomenon occurs. A person who has moved from a brightly lit room or open area with sunlight into a dark room, at first he sees nothing and it takes 20-30 minutes for him to navigate well enough in the dark.
This suggests that depending on the surrounding environment (lighting), a person’s visual sensitivity changes dramatically. As studies have shown, this change is very large, and the sensitivity of the eye when moving from bright light to darkness increases 200 thousand times!
Physiology knows well the mechanisms underlying this huge change sensitivity. In the functioning of the eye, these include a number of special mechanisms. Some of them boil down to the fact that different illumination changes the lumen of the pupil (the pupil expands in the dark and narrows in the light and can change its lumen 17 times), thus regulating the overall influx of light. Another mechanism is that in the retina of the eye there is a movement of pigment, which forms a kind of barrier that protects against excessive penetration of light rays into the sensitive layer. Equally important to increase the sensitivity of the retina in the dark, it has a process of restoring visual purple - the most important light-sensitive substance that is part of the light-sensitive cells of the retina. As shown by special studies (77. G. Snyakin), the retina of the eye also has a special mechanism to “mobilize” maximum number active photosensitive elements in the dark and “demobilize”, or turn off, a significant number of active photosensitive elements in the light, so the sensitivity of the retina is different time day and night and even at different times of the year changes. Finally, significant functional changes occur in the retina of the eye, which boils down to the fact that in light conditions (during the day) less sensitive light-sensitive devices - “cones” - are activated, which, however, are capable of distinguishing colors, while in twilight they are turned off. Other retinal devices remain active - rods, which have greater sensitivity, but cannot distinguish color shades; the fact that at dusk a person ceases to distinguish colors, although his vision becomes sharper, is explained precisely by this fact.
Along with the described peripheral mechanisms for changing sensitivity, there are also central mechanisms that allow you to regulate the severity of sensitivity depending on environmental conditions. These include mechanisms that change the tone of the cortex under the influence of impulses entering it through the fibers reticular formation.
The described changes in sensitivity, depending on environmental conditions and called adaptation of the senses to environmental conditions, also exist in the auditory sphere (changes in auditory sensitivity in conditions of silence and noise), in the sphere of smell, touch and taste.
A change in sensitivity that occurs according to the type of adaptation does not occur immediately; it requires a certain amount of time and has its own time characteristics.
It is important that these time characteristics are different for different organs feelings. Thus, we know well that in order for vision in a dark room to acquire the necessary sensitivity, about 30 minutes must pass, and only after that a person acquires the ability to navigate well in the dark. The process of adaptation of the auditory organs goes much faster. Human hearing adapts to the surrounding background within 15 s. A change in sensitivity in the sense of touch also occurs quickly (a slight touch to the skin ceases to be perceived after just a few seconds).
The phenomena of thermal adaptation (getting used to temperature changes) are well known, but these phenomena are clearly expressed only in the average range, and getting used to extreme cold or extreme heat, as well as to painful irritations, almost does not occur. The phenomena of adaptation to odors are also known. The change in sensitivity in these cases occurs more slowly, for example, the smell of camphor ceases to be felt after 1-2 minutes; It is characteristic that adaptation to pungent odors that cause painful stimulation (including the trigeminal component) does not occur at all.
Adaptation is one of the most important species changes in sensitivity, indicating greater plasticity of the organism in its adaptation to environmental conditions.
2. Sensitization. The process of sensitization differs from the process of adaptation in two respects. On the one hand, if in the process of adaptation sensitivity changes in both directions, increasing and decreasing its severity, then in the process of sensitization it changes only in the direction of increasing severity. On the other hand, if changes in sensitivity during adaptation depend on conditions environment, then during sensitization they depend primarily on changes in the organism itself - physiological or psychological.
There are two main aspects of increasing sensitivity according to the type of sensitization:
a) one of them is long-term, permanent and depends primarily on sustainable changes occurring in the body;
b) the second of them is temporary and depends on emergency effects on the subject’s condition - physiological or psychological.
The first group of conditions that change sensitivity includes age, typological conditions, endocrine changes and general state subject associated with fatigue.
Age subject is clearly associated with changes in sensitivity. Studies have shown that the sensitivity of the sensory organs increases with age, reaching its maximum by 20-30 years, in order to gradually decrease thereafter. This process reflects the overall dynamics of work nervous system body.
Essential features of the functioning of the sense organs depend on type of nervous system subject. It is known that people with strong nervous system, show greater endurance and stability, while people with weak nervous system, with less endurance they have greater sensitivity (B.M. Teploye).
Very great importance for sensitivity has endocrine balance body. It is known that during pregnancy, olfactory sensitivity can sharply worsen, while the acuity of visual and auditory sensitivity decreases.
It should, of course, be mentioned those significant phenomena of increased sensitivity that occur with certain endocrine disorders, for example, with hyperfunction of the thyroid gland.
Noticeable changes in sensitivity may finally occur in conditions fatigue. Fatigue, which causes inhibitory (phase) states of the cortex, may first cause an exacerbation of sensitivity, so that when it further development proceed to decrease sensitivity.
It should also be pointed out that long-term and stationary changes in sensitivity can occur during an asthenic state of the nervous system, known as “irritable weakness,” on the one hand, and during the classical phenomena of hysteria, on the other.
The second group differs from these stationary changes in sensitivity - those forms of change (exacerbation) of sensitivity that are caused by emergency factors and are, as a rule, relatively short-term in nature.
The factors causing emergency sensitization include, first of all, pharmacological effects. It is known that there are substances that cause a distinct exacerbation of sensitivity. Such factors include, for example, adrenalin, the use of which causes stimulation of the autonomic nervous system and, through the reticular formation, can cause a distinct aggravation of sensitivity. Phenamine (benhydrin) and a number of other substances can have a similar effect, exacerbating the sensitivity of receptors. On the contrary, there are substances, the use of which leads to a clear decrease in sensitivity, such substances include, for example, pilocarpine.
Over the past decades, the use of pharmacological agents as ways to regulate the functioning of the nervous system and, in particular, changes in sensitivity has accumulated a lot of experience, and a number of new drugs can be named that have a significant impact on the regulation of the functioning of the sensory organs.
Pharmacological effects are not the only way cause emergency sensitization of sensations. Another way is interaction of sensations.
We have already mentioned that an impact on one of the perceiving organs can cause an increase in the sensitivity of another organ. Yes, academician P. P. Lazarev showed that if a prolonged tone is heard in the audience, then turning on the light causes the sound of the tone to begin to seem more intense. On the contrary, when exposed to strong noise, light sensitivity may decrease. Quite weak stimuli of the same analyzer can also have a sensitizing ability to change sensitivity. Thus, if illumination of the periphery of the retina with weak light can increase the sensitivity of other parts of the retina, then illumination of one eye increases the sensitivity of the other eye. Finally, a number of experiments have shown that sound stimulation, and sometimes skin irritation, can cause an increase in visual sensitivity.
All these experiments not only show the close interaction of individual forms of sensations, but also open the way for more complex conditioned reflex increased sensitivity.
A number of experiments showing this possibility were carried out by the famous Soviet physiologist A. O. Dolin.
It turned out that if you first give the subject the sound of a metronome, it does not have a significant effect on the change in light sensitivity, but if you combine this sound with illumination of the eye several times in a row, then after a while the use of this sound alone will cause a decrease in sensitivity.
It is characteristic that similar changes in sensitivity can be caused if a word is used as a conditioned stimulus. This effect is especially clear if, before testing the sensitivity of the eye, one pronounces a word that in the subject’s past experience took on the meaning of light. In the experiments of A. O. Dolin, it was shown that a similar change in sensitivity occurred in the case when, before measuring sensitivity, the subject uttered the word “flame”, but this effect did not occur if the researcher uttered a word similar in sound, but having a different meaning, for example the word "tribe".
All these experiments show how great the possibilities are with which it is possible to induce changes in sensitivity using physiological (including conditioned reflex) techniques.
Significant changes in sensitivity can, however, be caused by the latter - psychological by changing the interests or “attitudes of the subject.”
We already know that the animal is particularly sensitive to biologically significant significant influences. The same phenomenon can be traced in humans if, without changing physical features irritations acting on him, using verbal instructions to change them significance.
We can give just a few examples of how changing the significance of a stimulus can significantly increase sensitivity (or reduce absolute thresholds perception of irritation).
Case in point Experiments conducted in the laboratory of the famous Soviet psychophysiologist G.V. Gershuni can serve as an example. In these experiments, the subject was offered two illuminated squares, between which a weak (non-perceptible) light point was located. Under normal conditions, the subject did not perceive this point. When this light point was reinforced by a painful stimulus, while another combination of two illuminated squares, between which there was no weak light point, was not reinforced by any stimulus and, therefore, subthreshold light stimulation became the only sign by which the combination could be distinguished , accompanied by pain, from an indifferent combination, that weak point of light began to be perceived by the subject. It is easy to see that this experiment clearly demonstrates the possibility of sharpening sensitivity by giving a weak nodal irritation a signal value.
A similar increase in sensitivity can, however, be achieved with the help of a simple speech instruction, in which an important “signal” meaning is attached to a poorly distinguishable feature. A demonstration experiment was carried out Soviet psychologists A.V. Zaporozhets and T.V. Epdovitskaya. Experiments conducted on children preschool age, was devoted to research into how assigning significance to a known stimulus increased acuity visual perception. As methods for assessing the acuity of visual perception, open rings were used, in which the gap is located either at the top or at the bottom (the so-called Landoldt rings, used in the practice of ophthalmologists).
In one experiment, children were asked to judge the position of a gap by pressing one button if the gap was at the bottom and another if it was at the top. In another, an estimate of the position of this gap was included in the game: the Landoldt circle was placed above the goal, from which correct definition the gap position, a toy car drove out.
Experience has shown that if the speech instruction, which gave the position of the gap the meaning of a signal, did not yet affect the acuity of visual sensitivity in young children, then in children 5-6 years old and older it had a significant effect. Children who, under the conditions of an indifferent experiment, distinguished the position of the break in the Landoldt ring only at a distance of 200-300 cm, after giving this position the value of the corresponding signal, caught the position of this break at a distance of 310-320 cm.
These experiments, showing how giving a signal value to a stimulus can sharpen sensitivity, are of great importance psychological significance, being an example of that exceptional plasticity in the work of our senses, changing depending on the meaning of the stimulus.
An increase in the acuity of sensitivity under the influence of the value of a perceived sign can take place not only in absolute terms, but also in relative sensitivity.
Thus, it is well known that distinguishing shades of color, minor changes tone or minimal taste changes can be sharply aggravated as a result professional activity. It has been established that dyers can distinguish up to 50-60 shades of black; steelworkers distinguish the subtlest shades of a hot metal flow, which indicate the slightest change in foreign impurities, the distinction of which remains inaccessible to an outside observer. It is known how subtle the distinction of taste nuances can be achieved by tasters who are able to determine the type of wine or tobacco by the slightest nuances of tasting, and sometimes even say on which side of the gorge the grapes from which the wine is made grew. Finally, it is known what subtlety the distinctive sensitivity to sounds can be achieved in musicians, who become capable of perceiving differences in tones that are completely imperceptible to the ordinary listener.
All these facts show that in conditions of development complex shapes conscious activity, the acuity of absolute and differential sensitivity can change significantly and that the inclusion of one or another feature in conscious activity a person can significantly change the severity of this sensitivity.