Touch - One of the five main types of senses in humans, consisting of the ability to feel physical touch on objects, to perceive something with receptors located in the skin, muscles, and mucous membranes.

Touch is a collective concept. In principle, it would be possible to distinguish not one, but several independent types of sensations, because they have a different nature:

- sensations of touch,

– sensations of pressure,

– sensations of vibration,

– feeling of texture,

- sensations of extension.

Tactile sensations are provided by the work of two types of skin receptors:

– nerve endings surrounding the hair follicles,

– capsules consisting of connective tissue cells.

Visual and auditory perception are characterized by a field (volumetric) feature: we perceive the entire piece of space surrounding us. That is, we simultaneously see many different objects in front of us, which at the same time may be in certain relationships with each other. We perceive at once all the sounds around us that our ear can sense. If a bright flash occurs in front of our eyes or some object makes a sharp sound, we will turn our attention to it.

Touch does not have such a field character. With its help, we receive information only about those objects with which we are in physical contact. The only exception is, perhaps, the sensation of vibration - we can remotely feel with our skin strong vibrations excited by some distant object.

If an object located just a few centimeters from us suddenly suddenly changes its shape (for example, the legs of a compass move apart) or its temperature (for example, a spoon heats up on the flame of a burner), we will not even notice it if we use only the means of touch . Touch, of course, gives us a lot in life. However, for the knowledge of objective reality, as S. L. Rubinstein noted, touch plays only a subordinate role. He also noted that what is really essential for the knowledge of reality is not the passive touch of something on a person’s skin, but the active touch, the feeling by a person of the objects around him, associated with the impact on them. With touch, cognition of the material world occurs in the process of movement, which turns into a consciously purposeful action of feeling, effective cognition of an object.

The sense of touch includes sensations of touch and pressure in unity with kinesthetic, muscle-articular sensations. Touch is both extero- and proprioceptive sensitivity, the interaction and unity of one and the other. Proprioceptive components of touch come from receptors located in muscles, ligaments, and joint capsules (Pacinian corpuscles, muscle spindles). When moving, these receptors are stimulated by changes in voltage.

A person has a very specific organ of touch - the hand. The hand, even in a passive state, is capable of giving us a lot of tactile information, but, of course, the main cognitive value lies precisely in the moving hand. The hand is both an organ of human labor and, at the same time, an organ of cognition of objective reality.

The hand differs from other parts of the body in that:

– sensitivity to touch and pressure on the palm and fingertips is many times greater than on the back or shoulder,

– being an organ formed in work and adapted to influence objects of objective reality, the hand is capable of active touch, and not only the reception of passive touch,

– has an extensive projection in the cerebral cortex.

S. L. Rubinstein notes that the hand determines the following basic properties of the material body with which it comes into contact:

– hardness,

– elasticity,

– impenetrability.

The distinction between hard and soft, for example, is made by the resistance that the hand encounters when in contact with the body, which is reflected in the degree of pressure of the articular surfaces on each other. Tactile sensations (touch, pressure, together with muscular-articular, kinesthetic sensations), combined with diverse data of skin sensitivity, reflect many other properties through which we recognize objects in the world around us:

– the interaction of sensations of pressure and temperature gives us the sensation of humidity,

– the combination of moisture with some pliability or permeability allows us to recognize liquid bodies as opposed to solids,

– the interaction of sensations of deep pressure is characteristic of the sensation of soft,

– in interaction with the thermal sensation of cold, they generate a feeling of stickiness,

– we recognize the roughness and smoothness of a surface as a result of vibrations that are produced when moving the hand along the surface, and differences in pressure on adjacent areas of the skin.

From early childhood, already in an infant, the hand is one of the most important organs of cognition of the environment. The baby reaches out with his little hands to all objects that attract his attention. Preschoolers and often younger schoolchildren, too, when they first become acquainted with an object, grab it with their hands, actively turn it, move it, and lift it. These same moments of effective familiarization in the process of active cognition of an object also take place in an experimental situation.

From infancy, a person’s sense of touch functions in close connection with vision and under its control. When a person, unfortunately, is deprived of vision as a result of blindness, the sense of touch also develops, it seeks to compensate for the lack of vision, but it takes much more time to perceive space and individual objects, and often the picture remains incomplete. It is difficult, for example, for a blind person to know the shape of a tree or the size of a house. However, with due diligence, some objects can be recognized surprisingly accurately by the blind and deaf-blind. This is confirmed by sculptures by blind artists.

Palpation is involved in the perception of speech by deaf-blind people. “Listening” to speech by deaf-blind and mute people using the “voice-reading” method consists in the fact that the deaf-blind person puts his hand with the back of his hand to the speaker’s neck in the area of ​​the vocal apparatus and, through tactile-vibrational perception, catches speech.

All people tactile sensations may evoke certain emotions. Usually this connection is conditioned reflex in nature (that is, it is the result of experience). The interesting thing is that people vary quite a lot in the degree of “emotionality of touch”. For many people, tactile sensations do not evoke any noticeable emotions at all. Many, on the contrary, are too “fixated” on their tactile sensations.

Signaling about what is happening at a given moment in time in the environment around us and in our own body. It gives people the opportunity to navigate the conditions that surround them and connect their actions and actions with them. That is, sensation is cognition environment.

Feelings - what are they?

Sensations are a reflection of certain properties that are inherent in an object, with their direct impact on human or animal senses. With the help of sensations, we gain knowledge about objects and phenomena, such as, for example, shape, smell, color, size, temperature, density, taste, etc., we capture various sounds, comprehend space and make movements. Sensation is the primary source that gives a person knowledge about the world around him.

If a person were deprived of absolutely all senses, then he would not be able to understand the environment by any means. After all, it is sensation that gives a person the material for the most complex psychological processes, such as imagination, perception, thinking, etc.

For example, those people who are blind from birth will never be able to imagine what blue, red or any other color looks like. And a person who has been deaf since birth has no idea what his mother’s voice, the purr of a cat or the babbling of a stream sounds like.

So, sensation is in psychology what is generated as a result of irritation of certain sense organs. Then irritation is an effect on the sense organs, and irritants are phenomena or objects that in one way or another affect the sense organs.

Sense organs - what are they?

We know that sensation is a process of cognition of the environment. And with the help of what do we feel, and therefore understand the world?

Even in ancient Greece, five sense organs and sensations corresponding to them were identified. We have known them since school. These are auditory, olfactory, tactile, visual and gustatory sensations. Since sensation is a reflection of the world around us, and we use not only these senses, modern science significantly increased information about possible types of feelings. In addition, the term “sense organs” today has a conditional interpretation. “Sensation organs” is a more accurate name.

The endings of the sensory nerve are the main part of any sense organ. They are called receptors. Millions of receptors have sensory organs such as the tongue, eye, ear and skin. When a stimulus acts on a receptor, a nerve impulse occurs that is transmitted along the sensory nerve to certain areas of the cerebral cortex.

In addition, there is sensory experience that is generated internally. That is, not as a result of physical impact on the receptors. Subjective sensation is such an experience. One example of this sensation is tinnitus. In addition, the feeling of happiness is also a subjective feeling. Thus, we can conclude that subjective sensations are individual.

Types of sensations

In psychology, sensation is a reality that affects our senses. Today, there are about two dozen different sensory organs that reflect the impact on the human body. All types of sensations are the result of exposure to various stimuli on the receptors.

Thus, sensations are divided into external and internal. The first group is what our senses tell us about the world, and the second is what our own body signals to us. Let's look at them in order.

External senses include visual, gustatory, olfactory, tactile and auditory.

Visual sensations

This is a feeling of color and light. All objects that surround us have some color, while a completely colorless object can only be one that we cannot see at all. There are chromatic colors - various shades of yellow, blue, green and red, and achromatic - these are black, white and intermediate shades of gray.

As a result of the influence of light rays on the sensitive part of our eye (the retina), visual sensations arise. There are two types of cells in the retina that respond to color - rods (about 130) and cones (about seven million).

The activity of cones occurs only during the daytime, but for rods, on the contrary, such light is too bright. Our vision of color is the result of the work of cones. At dusk, rods become active, and a person sees everything in black and white. By the way, this is where the famous expression comes from: that all cats are gray at night.

Of course, the less light, the worse a person sees. Therefore, in order to prevent unnecessary eye strain, it is strongly recommended not to read at dusk or in the dark. Such strenuous activity has a negative impact on vision and may lead to the development of myopia.

Auditory sensations

There are three types of such sensations: musical, speech and noise. In all these cases, the auditory analyzer identifies four qualities of any sound: its strength, pitch, timbre and duration. In addition, he perceives the tempo-rhythmic features of sounds perceived sequentially.

Phonemic hearing is the ability to perceive speech sounds. Its development is determined by the speech environment in which the child is raised. Well-developed phonemic hearing significantly influences the accuracy of written speech, especially during primary school, while a child with poorly developed phonetic hearing makes many mistakes when writing.

A baby’s musical ear is formed and develops in the same way as speech or phonemic hearing. The early introduction of a child to musical culture plays a huge role here.

A certain emotional state of a person can create various noises. For example, the sound of the sea, rain, howling wind or rustling leaves. Noises can serve as a signal of danger, such as the hiss of a snake, the noise of an approaching car, or the menacing barking of a dog, or they can signal joy, such as the thunder of fireworks or the footsteps of a loved one. In school practice, they often talk about the negative impact of noise - it tires the student’s nervous system.

Skin sensations

Tactile sensation is the sensation of touch and temperature, that is, the feeling of cold or warmth. Each type of nerve endings located on the surface of our skin allows us to feel the temperature of the environment or touch. Of course, the sensitivity of different areas of the skin varies. For example, the chest, lower back and abdomen are more susceptible to the feeling of cold, and the tip of the tongue and fingertips are most susceptible to touch; the back is least susceptible.

Temperature sensations have a very pronounced emotional tone. So, positive feeling are accompanied by average temperatures, despite the fact that the emotional colors of heat and cold differ significantly. Warmth is regarded as a relaxing feeling, while cold, on the contrary, is invigorating.

Olfactory sensations

Olfaction is the ability to sense smells. In the depths of the nasal cavity there are special sensitive cells that help recognize odors. Olfactory sensations modern man play a relatively small role. However, for those who are deprived of any sense organ, the rest work more intensely. For example, deaf-blind people are able to recognize people and places by smell and receive signals of danger using their sense of smell.

The sense of smell can also signal to a person that danger is nearby. For example, if there is a smell of burning or gas in the air. A person’s emotional sphere is greatly influenced by the smells of the objects around him. By the way, the existence of the perfume industry is entirely determined by the aesthetic need of a person for pleasant smells.

The senses of taste and smell are closely related to each other, since the sense of smell helps determine the quality of food, and if a person has a runny nose, then all the dishes offered will seem tasteless to him.

Taste sensations

They arise due to irritation of the taste organs. These are the taste buds, which are located on the surface of the pharynx, palate and tongue. There are four main types of taste sensations: bitter, salty, sweet and sour. A series of shades that arise within these four sensations gives the taste originality to each dish.

The edges of the tongue are sensitive to sour, its tip to sweet, and its base to bitter.

It should be noted that taste sensations are significantly influenced by the feeling of hunger. If a person is hungry, then tasteless food seems much more pleasant.

Internal sensations

This group of sensations lets a person know what changes are occurring in his own body. Interoceptive sensation is an example of an internal sensation. It tells us that we experience hunger, thirst, pain, etc. In addition, there are also motor, tactile sensations and a sense of balance. Of course, interoceptive sensation is an extremely important ability for survival. Without these sensations, we would know nothing about our own body.

Motor sensations

They determine that a person feels the movement and position in space of parts of his body. With the help of the motor analyzer, a person has the ability to feel the position of his body and coordinate its movements. Receptors of motor sensations are located in the tendons and muscles of a person, as well as in the fingers, lips, and tongue, because these organs need to make subtle and precise working and speech movements.

Organic sensations

This type of sensation tells us how the body works. Inside organs, such as the esophagus, intestines and many others, there are corresponding receptors. While a person is healthy and well-fed, he does not feel any organic or interoceptive sensations. But when something is disrupted in the body, they manifest themselves in full. For example, abdominal pain appears if a person has eaten something that is not very fresh.

Tactile sensations

This type of feeling is caused by the fusion of two sensations - motor and skin. That is, tactile sensations appear when you feel an object with a moving hand.

Equilibrium

This sensation reflects the position that our body occupies in space. In the labyrinth of the inner ear, which is also called the vestibular apparatus, when the body position changes, lymph (a special fluid) oscillates.

The organ of balance is closely related to the work of other internal organs. For example, with strong stimulation of the balance organ, a person may experience nausea or vomiting. This is otherwise called air sickness or seasickness. The stability of the balance organs increases with regular training.

Painful sensations

The feeling of pain has a protective value, as it signals that something is wrong in the body. Without this type of sensation, a person would not even feel serious injuries. The anomaly is considered complete insensitivity to pain. It does not bring anything good to a person, for example, he does not notice that he is cutting his finger or putting his hand on a hot iron. Of course, this leads to permanent injuries.

The five senses allow us to perceive the world around us and respond in the most appropriate way. The eyes are responsible for vision, the ears are for hearing, the nose is for smell, the tongue is for taste, and the skin is for touch. Thanks to them, we receive information about our environment, which is analyzed and interpreted by the brain. Usually our reaction is aimed at prolonging pleasant sensations or ending unpleasant ones.

Vision

Of all the senses available to us, we most often use vision. We can see through many organs: light rays pass through the pupil (hole), the cornea (a transparent membrane), then through the lens (a lens-like organ), after which an inverted image appears on the retina (the thin membrane in the eyeball). The image is converted into a nerve signal thanks to the receptors lining the retina - rods and cones, and is transmitted to the brain through the optic nerve. The brain recognizes the nerve impulse as an image, turns it in the right direction and perceives it in three dimensions.

Hearing

According to scientists, hearing- the second most used sense by a person. Sounds (air vibrations) penetrate through the ear canal to the eardrum and cause it to vibrate. They then pass through the fenestra vestibule, an opening covered by a thin film, and the cochlea, a fluid-filled tube, irritating the auditory cells. These cells convert the vibrations into nerve signals that are sent to the brain. The brain recognizes these signals as sounds, determining their volume level and pitch.

Touch

Millions of receptors located on the surface of the skin and in its tissues recognize touch, pressure or pain, then send appropriate signals to the spinal cord and brain. The brain analyzes and deciphers these signals, translating them into sensations - pleasant, neutral or unpleasant.

Smell

We are able to distinguish up to ten thousand odors, some of which (poisonous gases, smoke) notify us of imminent danger. Cells located in the nasal cavity detect molecules that are the source of odor, then send corresponding nerve impulses to the brain. The brain recognizes these odors, which can be pleasant or unpleasant. Scientists have identified seven main odors: aromatic (camphor), ethereal, fragrant (floral), ambrosial (the smell of musk - an animal substance used in perfumery), repulsive (putrefactive), garlicky (sulphuric) and, finally, the smell of burnt. The sense of smell is often called the sense of memory: indeed, a smell can remind you of a very long ago event.

Taste

Less developed than the sense of smell, the sense of taste informs about the quality and taste of the food and liquids consumed. Taste cells located on the taste buds, small tubercles on the tongue, detect flavors and transmit corresponding nerve impulses to the brain. The brain analyzes and identifies the nature of taste.

How do we taste food?

The sense of taste is not enough to evaluate food, and the sense of smell also plays a very important role. important role. The nasal cavity contains two odor-sensitive olfactory areas. When we eat, the smell of food reaches these areas, which "determine" whether the food tastes good or not.

The main type of somesthesia is tactile sensitivity. It includes the sensations of touch, pressure and vibration.

Tactile sensitivity receptors end in the second layer of skin. They come in two types. In the hairy parts of the skin, the nerve endings go directly to the hair follicles. In hairless ones, they end in capsules consisting of connective tissue cells. A number of such capsules are known: Meissner's corpuscles (touch), Merkel discs (touch), Golgi-Massoni corpuscles (touch, pressure), Pacinian corpuscles (touch, pressure), etc.

Regardless of the presence of special capsules, the thresholds for activation of sensory nerves are approximately the same. This suggests that these capsules cannot be considered as receptors for certain qualities of tactile sensations.

The irritant of skin mechanoreceptors is the movement of surrounding tissues. American researcher J. Neff observed through a microscope the movement of a weight placed on the skin, and at the same time recorded the messages of the subject. It turned out that the sensation of touch lasts only as long as the load is immersed in the skin and stops when the resistance of the skin equalizes its weight. When part of the load is removed so that it rises somewhat upward, the sensation of touch reappears for a short time. These observations were also fully confirmed in experiments with recording the activity of individual sensory fibers (J. Naf and D. Kenshalo, 1966).

Histological studies have shown that the density of tactile receptors in different areas of the skin corresponds to their functional importance for the sense of touch. There are 29 receptors in one square millimeter of the dorsum of the hand, 50 of the forehead, 100 of the tip of the nose, and 120 of the tip of the thumb.

The sensory pathways of tactile sensitivity mainly consist of thick (fast) fibers. They are part of the lemniscal system of pathways (Fig. 89). Due to the fact that the pathways of tactile sensitivity differ from the paths of pain and temperature, with some lesions of the spinal cord, selective loss of one or another type of somesthesia is possible.

Fibers of tactile sensitivity, switching in the medulla oblongata and thalamus, end in the postcentral gyrus of the cerebral cortex. Numerous studies, among which the work of the Canadian neurosurgeon W. Penfield should be noted, have made it possible to establish that individual areas of the body are represented in the postcentral gyrus according to a functional, and not just a topographical basis (Fig. 90). The data underlying such brain maps was obtained in two ways: on the basis of the subjects’ subjective report of the sensations arising from irritation of certain points of the brain, and strictly objectively - by recording cortical responses caused by irritation of certain areas of the skin. Both types of data are completely consistent with each other.

Rice. 89.

Psychophysical studies of tactile sensitivity are associated both with the analysis of various qualities of sensations and with the measurement of thresholds depending on the location of stimulation. Table 3 presents the absolute thresholds for the sensation of pressure for different areas of the skin. Differential pressure thresholds vary from 0.14 to 0.40.

Another method for assessing tactile sensitivity is to measure the maximum distance between two simultaneously irritated points of the skin, at which the subject still thinks that only one point is irritated. Since the time of E. H. Weber, a compass-like instrument called an aesthesiometer has been used for these studies. Some of the threshold values ​​for spatial acuity of touch are presented in Table 4. As can be seen, these data again reflect the functional significance of certain areas of the body.

Rice. 90.

Schematic representation of sensory projections of various parts of the body into the postcentral gyrus of the cerebral cortex To emphasize the spatial picture of the mechanical forces acting on the skin, the phenomenon of mutual inhibition discovered by G. Bekosi (1959) is of great importance

Table 3 - Touch sensation thresholds for various skin areas (in grams per mm2)

Table 4 - Spatial thresholds of touch for different areas of the skin (in mm)

nearby tactile stimuli. This phenomenon is similar to the phenomenon of lateral inhibition and therefore the analysis given earlier on page 114 is valid for it.

The existence of lateral inhibition in the tactile sphere may explain the fact that the localization error of a single stimulus is, as a rule, noticeably smaller than the spatial acuity of touch (E. Boring, 1942).

Tactile sensitivity is characterized not only by spatial, but also by temporal acuity. To assess the temporal resolution of touch, special gears or electric vibrators are used that can stimulate the skin with varying frequencies and strengths. The thresholds obtained in this way also obey the principle of functional organization. With a sufficiently strong amplitude, vibrations with a frequency of up to 12,000 Hz are perceived separately. The involvement of other perceptual systems in vibration sensitivity has been discussed previously (see page 54).

Temporal resolution is important for tactile sensory functions such as distinguishing between smooth and rough surfaces. The German psychologist D. Katz (1925) found that subjects successfully distinguished types of paper by very subtle differences in the quality of its surface. Thus, subjects could notice paper irregularities equal to only 0.02 mm. This is a higher sensitivity than the visual system. It is based on an orientation towards the difference in vibration sensations that arise when the fingers move on the surface of an object.

At present, too little is known about how we can “touch” determine such properties of objects as wetness or dryness, hardness or softness. There is no doubt, however, that these types of perceptions are not reduced to the stimulation of any specialized receptors, but are the result of complex processing of sensory information, including both more elementary (temperature) and more complex (kinesthesia) components.