Processes of sensations in psychology. Topic: Types of sensations
14. Feeling. Neurophysiological mechanisms of sensations. Classification of sensations. Patterns of sensations. Features of types of sensations.
1. Sensation - mentally and the process of direct, sensory reflection of the elementary (physical and chemical) properties of reality; human sensitivity to sensory influences of the environment. All complex human mental activity is based on sensations. Sensation is an elementary but basic mental process. It is not a passive imprint of the physical properties of reality, but an active mental process of human interaction with the world.
Sensations reflect not only the specific properties of objects and phenomena, but And their intensity, duration And spatial localization. Human sensations are interconnected and associated in the same way that various properties of reality are interconnected.
The process of continuous reception and analysis of information on physical and chemical characteristics external environment and internal states of the body is carried out through analyzers. The information received by analyzers is called sensory(from lat. sensus - feeling), and the process of its reception and primary processing - sensory activity.
Each sense organ (eye, ear, sensitive skin cells, taste buds of the tongue) is specialized in receiving and processing various specific external influences.
The main part of each sense organ, the ending of the sensory nerve, is receptors(from lat. receptor - receiving). They convert the energy of an external stimulus into a nerve impulse. Sensation is an act of transition from external influence and a fact of consciousness.
2. Depending on receptor locations all sensations are divided into three groups:
♦ the first group includes sensations associated with receptors located on the surface of the body - visual, auditory, olfactory, gustatory and skin; This exteroceptive sensations;
♦ the second group includes interoceptive Feel; they are associated with receptors located in the internal organs (organic sensations);
♦ the third group includes kinethestic (motor) and static sensations, the receptors of which are located in the muscles, ligaments and vestibular apparatus; This - proprioceptive sensations (from lat. propnus - own), sensations of one’s own movements and spatial position of the body.
Depending on the types of analyzer The following types of sensations are distinguished: visual, auditory, skin, olfactory, gustatory, kinesthetic, static, vibration, organic, pain.
Sensations are also divided into distant(reflection of properties of deleted objects) and contact.
General psychophysiological patterns of sensations
The operation of each analyzer has specific patterns. Along with this, all types of sensation are subject to general psychophysiological laws. These include:
♦ sensitivity thresholds;
♦ adaptation;
♦ sensitization;
♦ contrast of sensations;
♦ synesthesia.
1. Sensitivity thresholds are its maximum capabilities. The range of our sensitivity is limited by the lower and upper absolute thresholds:
♦ the minimum intensity of stimulation required to produce a barely noticeable sensation is called absolute bottom threshold of sensation;
♦ upper absolute sensation threshold is the maximum value of irritation, a further increase in which causes pain or disappearance of sensation.
Along with the absolute it differs relative sensitivity- sensitivity to changes in the intensity of exposure. Relative sensitivity is measured threshold of discrimination(difference threshold) - the minimum difference in the strength of two stimuli of the same type/!, necessary to change the intensity of sensation.
Varies operational sensation thresholds- the magnitude of the signal at which the accuracy and speed of its discrimination reach a maximum (this value is an order of magnitude greater than the value of the lower threshold).
2. A change in the sensitivity of the analyzer as a result of its adaptation to the strength of the duration of the current stimulus is called adaptation.
Different analyzers have different speed And range adaptation. Adaptation to some stimuli occurs faster, to others - slower: faster olfactory and tactile analyzers adapt, slower - auditory, gustatory and visual analyzers.
3. Increasing the sensitivity of analyzers under the influence of internal (mental) factors is called sensitization.
Sensitization, exacerbation of sensitivity, can be caused by:
♦ interaction of sensations;
♦ physiological factors;
♦ the expectation of one or another influence, its significance, a special attitude towards distinguishing certain stimuli;
♦ exercise, experience.
In people deprived of any type of sensitivity, this deficiency is compensated (compensated) by increasing the sensitivity of other organs (for example, increasing auditory and olfactory sensitivity in the blind). This is the so-called compensatory sensitization.
Strong stimulation of some analyzers reduces the sensitivity of others. This phenomenon is called desensitization.
4. One of the manifestations of the interaction of sensations is their contrasting interaction. Contrast of sensations is an increase in sensitivity to one properties under the influence of other, opposite properties of reality. Thus, the same figure of the same color appears gray on a light background, and white on a black background.
5. Synesthesia (from Greek. sinaisthcsis - joint sensation) - an associative (phantom) sensation that accompanies the real one (the sight of a yellow lemon causes a sour sensation).
Features of certain types of sensations
1. Visual sensations. For visual sensations to occur, electromagnetic waves must act on the visual receptor—the retina, a collection of photosensitive nerve cells located at the bottom of the eyeball.
Human-perceived colors are divided into chromatic And achromatic - colorless (black, white and intermediate shades of gray).
Light (electromagnetic) waves of different lengths cause different color sensations. Color - This is a mental phenomenon, a human sensation caused by different lengths of electromagnetic radiation.
Exists three-component theory of color vision, according to which all the variety of color sensations arises as a result of the work of three types of two-perceptive receptors: red, green and blue.
Visual stimulation is characterized by some inertia. This is the reason for the short-term (0.25 s) persistence of a trace of light stimulation after the cessation of exposure to the stimulus.
The color of each object is characterized by those rays of the light spectrum that the object reflects.
2. Auditory sensations. The work of the auditory analyzer is no less complex and important than the work of the visual analyzer. The main flow of speech information goes through this channel.
The auditory analyzer is sensitive to the pitch, strength and timbre of sound.
A person does not feel low frequency sounds (infrasounds). However, subthreshold low-frequency sounds affect a person’s mental state.
Sounds lying beyond the upper threshold of sound sensitivity (that is, above 20 thousand Hz) are called ultrasounds. Ultrasonic frequencies available to animals V 60 and even 100 thousand Hz. In our speech, sounds up to 140 thousand Hz are detected. It can be assumed that they are perceived by us on a subconscious level and carry emotional information.
Intensity of auditory sensation - volume - depends on the intensity of the sound, that is, on the amplitude of vibrations of the sound source and on the pitch of the sound.
In addition to pitch sensitivity, there are lower and upper thresholds of sensitivity to sound intensity.
Tactile sensations are sensations of touch. Tactile receptors are most numerous on the tips of the fingers and tongue.
Kinesthetic (motor) sensations. Our movements are associated with kinesthetic sensations.
Static sensation - a sense of the position of the body in space relative to the direction of gravity, a sense of balance. The receptors for these sensations (gravntoreceptors) are located in the inner ear.
Vibration sensations arise as a result of the reflection of vibrations from 15 to 1500 Hz in an elastic medium. These vibrations are reflected by all parts of the body. Vibrations are tiring and even painful for humans, and many of them are unacceptable.
Olfactory sensations arise as a result of irritation by particles of odorous substances in the air of the mucous membrane of the nasal cavity, where the olfactory cells are located.
Taste sensations. All the diversity of taste sensations consists \street combinations of four flavors: bitter, salty, sour And sweet.
Taste receptors are nerve endings located on the surface of the tongue - taste buds. They are located unevenly on the surface of the tongue.
Temperature sensations arise from irritation of skin thermoreceptors. There are separate receptors for sensation heat And cold.
Painful sensations are caused by mechanical, temperature and chemical influences that have reached superthreshold intensity.
Organic sensations are sensations associated with interoreceptors located in the internal organs. These include feelings of satiety, hunger, suffocation, nausea, etc.
4. Sensory organization of personality. The levels of development of individual types of sensitivity inherent in an individual and the features of their systemic functioning are called the sensory organization of personality. Each person has anatomical and physiological prerequisites (inclinations) for the development of certain sensory abilities. Individual people - psychics ~ have phenomenal sensitivity. The development of a person’s sensory culture is associated with his ability to respond to the harmony of colors, smells and sounds.
The need for harmonized sensory input is one of the basic human needs. Long-term sensory deprivation(deprivation of sensory influences) causes mental disorder in a person. With a constant flow of nerve impulses entering the brain from the sense organs, every person lives in contact with the outside world.
- INTRODUCTION -
All information that a person receives in the process of cognition, he receives through sensory cognitive processes, which arise during direct interaction of the senses with environmental objects. Understanding the world around us begins with sensations. Sensation is the simplest cognitive process that ensures the functioning of all more complex processes. Sensations arise from the direct action of the properties and qualities of the external and internal environment on the senses. Information about the properties and qualities of objects and phenomena coming from the senses is reflected in our consciousness in the form of sensations and impressions.
Sensation is an elementary sensory cognitive process, reflecting in the form of perceptions the properties and qualities of objects that directly act on the senses. Sensation is a cognitive process, and perception is a form of reflection of a stimulus acting on the sense organs that has arisen in our consciousness. So, sensation is the process of converting information received by the senses into facts of consciousness. This information exists in our consciousness in the form of various perceptions: light, auditory, olfactory, gustatory and tactile.
Sensation as such is a rather complex mental phenomenon, as it seems at first glance. Despite the fact that this is a fairly studied phenomenon, the global nature of its role in the psychology of activity and cognitive processes is underestimated by humans. The sensations are widespread in ordinary life person, and in a continuous process cognitive activity for people it is an ordinary, primary form of psychological connection between the body and the environment.
Partial or complete absence of types of sensation (vision, hearing, taste, smell, touch) in a person prevents or inhibits his development.
Sensations are of great importance on the formation of such cognitive processes as speech, thinking, imagination, memory, attention and perception, as well as on the development of activity as a scientific type of human activity aimed at creating objects of material and spiritual culture, transforming one’s abilities, preserving and improving nature, and building society.
An object research - human sensations.
Item research - types of sensations.
The problem research is various classifications sensations in psychology.
Target work - analyze theoretical literature on the research problem, consider different kinds and classification of sensations.
Tasks:
1. Give general concept sensations in psychology.
2. Consider the properties and functions of sensations.
3. Consider the classifications of types of sensations that exist in psychological science.
The work consists of an introduction, two chapters, an experimental part, a conclusion and a list of references.
The experimental part is devoted to visual sensations.
1. General concept of sensations and their functions in psychology
1.1 Concept of sensation
Sensations allow a person to perceive signals and reflect the properties and signs of things in the external world and states of the body. They connect a person with the outside world and are both the main source of knowledge and the main condition for his mental development.
Sensation is one of the simplest cognitive mental processes. Various information about the state of the external and internal environment human body receives sensations through the senses. Sensation is the most important connection between a person and the surrounding reality.
The process of sensation arises as a result of the influence on the sense organs of various material factors, which are called stimuli, and the process of this influence itself is called irritation.
Sensations arise on the basis of irritability. Sensation is a product of development in the phylogenesis of irritability. Irritability is a common property of all living bodies to come into a state of activity under the influence of external influences (pre-psychic level), i.e. directly affecting the life of the organism. Irritation causes excitation, which travels along centripetal, or afferent, nerves to the cerebral cortex, where sensations arise. On early stage In the development of living things, the simplest organisms (for example, the slipper ciliate) do not need to distinguish between specific objects for their life activity - irritability is sufficient. At a more complex stage, when a living person needs to identify any objects that he needs for life, and, consequently, the properties of this object as necessary for life, this is where the transformation of irritability into sensitivity occurs. Sensitivity is the ability to respond to neutral, indirect influences that do not affect the life of the body (example with a frog reacting to a rustle). The totality of feelings creates elementary mental processes, processes of mental reflection.
There are two main forms of sensitivity, of which one depends on environmental conditions and is called adaptation, and the other depends on the conditions of the body’s state, called sensitization.
Adaptation (adjustment, adjustment) is a change in sensitivity in the process of adapting to environmental conditions.
There are three directions:
1) increased sensitivity under the influence of a weak stimulus, for example, dark adaptation of the eye, when within 10-15 minutes. sensitivity increases by more than 200 thousand times (at first we do not see objects, but gradually we begin to distinguish their outlines);
2) a decrease in sensitivity under the influence of a strong stimulus, for example, for hearing this occurs in 20-30 seconds; with continuous and prolonged exposure to the stimulus, the corresponding receptors adapt to it, as a result of which the intensity of nervous excitations transmitted from the receptors to the cortex begins to decrease, which is the basis of adaptation.
3) complete disappearance of sensation as a result of prolonged exposure to the irritant, for example, after 1-1.5 minutes, a person stops feeling any smell in the room.
Adaptation is especially manifested in the spheres of vision, hearing, smell, touch, taste and indicates greater plasticity of the organism, its adaptation to environmental conditions.
Sensitization is an exacerbation of sensitivity due to changes internal state the body under the influence of stimuli that arrive at the same time to other sense organs (for example, an increase in visual acuity under the influence of weak auditory or olfactory stimuli).
1.2 Properties of sensations
All sensations can be characterized in terms of their properties. Moreover, the properties can be not only scientific, but also common to all types of sensations. The main properties of sensations include: quality, intensity, duration and spatial localization, absolute and relative thresholds of sensations (Fig. 1).
Rice. 1. General properties sensations
It should be borne in mind that very often, when they talk about the quality of sensations, they mean the modality of sensations, since it is the modality that reflects the main quality of the corresponding sensation.
The intensity of the sensation is its quantitative characteristics and depends on the strength of the current stimulus and the functional state of the receptor, which determines the degree of readiness of the receptor to perform its functions. For example, if you have a runny nose, the intensity of perceived odors may be distorted.
The duration of a sensation is a temporary characteristic of the sensation that has arisen. It is also determined by the functional state of the sensory organ, but mainly by the time of action of the stimulus and its intensity. It should be noted that sensations have a so-called latent (hidden) period. When a stimulus acts on a sense organ, the sensation does not occur immediately, but after some time. The latent period of different types of sensations is not the same. For example, for tactile sensations it is 130 ms, for pain - 370 ms, and for taste - only 50 ms.
The sensation does not appear simultaneously with the onset of the stimulus and does not disappear simultaneously with the cessation of its effect. This inertia of sensations manifests itself in the so-called aftereffect. A visual sensation, for example, has some inertia and does not disappear immediately after the cessation of the action of the stimulus that caused it. (C) Information published on the site
The trace of the stimulus remains in the form of a consistent image. There are positive and negative sequential images. A positive sequential image corresponds to the initial irritation and consists in maintaining a trace of irritation of the same quality as the actual stimulus.
A negative sequential image consists in the emergence of a quality of sensation that is opposite to the quality of the stimulus that influenced it. (C) Information published on the site
For example, light-darkness, heaviness-lightness, warmth-cold, etc. The emergence of negative sequential images is explained by a decrease in the sensitivity of a given receptor to a certain influence.
And finally, sensations are characterized by the spatial localization of the stimulus. (C) Information published on the site
The analysis carried out by receptors gives us information about the localization of the stimulus in space, i.e. we can tell where the light is coming from, where the heat is coming from, or what part of the body the stimulus is affecting.
All the properties described above, to one degree or another, reflect quality characteristics sensations. However, no less important are the quantitative parameters of the main characteristics of sensations - the degree (thresholds) of sensitivity (Fig. 2).
Rice. 2. Sensitivity thresholds
It should be remembered that the same stimulus for one person may be lower, and for another – higher than the threshold of sensation. The weaker the stimuli that a person is able to sense, the higher his sensitivity. In other words, the lower the absolute threshold of sensations, the higher the absolute sensitivity, and vice versa.
So, sensation is the simplest mental process of reflecting a separate quality (property) of an object under the direct influence of stimuli on the perceiving part of the analyzer.
1. 3 Physiological mechanisms of sensations
The physiological basis of sensations is the activity of complex complexes of anatomical structures called analyzers. The concept of an analyzer (a device that performs the function of distinguishing external stimuli), was introduced by academician I.P. Pavlov. He also examined the structure of the analyzers and came to the conclusion that they consist of three parts:
1) Regional department, called a receptor (a receptor is the perceiving part of the analyzer, a socialized nerve ending, its main function is the transformation of external energy into a nervous process);
2) nerve pathways(afferent department - transmits excitation to the central department; efferent department - along it transmits the response from the center to the peripheral);
3) analyzer core- cortical sections of the analyzer (they are also called the central sections of the analyzers), in which the processing of nerve impulses coming from the peripheral sections occurs. The cortical part of each analyzer includes an area that represents a projection of the peripheral region (i.e., a projection of the sensory organ) in the cerebral cortex, since certain receptors correspond to certain areas of the cortex.
So, the organ of sensation is the central section of the analyzer.
For sensation to occur, all components of the analyzer must be used. If any part of the analyzer is destroyed, the occurrence of the corresponding sensations becomes impossible. Thus, visual sensations cease when the eyes are damaged, when the integrity of the optic nerves is damaged, and when the occipital lobes of both hemispheres are destroyed. In addition, for sensations to arise, 2 more conditions must be present:
· Sources of irritation (irritants).
· Medium or energy that is distributed in the environment from the source to the subject.
For example, in a vacuum there are no auditory sensations. In addition, the energy emitted by the source may be so small that a person does not feel it, but it can be registered by instruments. That. Energy, in order to become perceptible, must reach a certain threshold value of the analyzer system.
Also, the subject may be awake or asleep. This should also be taken into account. During sleep, the thresholds of analyzers increase significantly.
So, sensation is a mental phenomenon that is the result of the interaction of an energy source with the corresponding human analyzer. In this case, we mean an elementary single source of energy that creates a homogeneous sensation (of light, sound, etc.).
Five conditions must exist for sensations to occur:
· Receptors.
· Analyzer nucleus (in the cerebral cortex).
· Conducting pathways (with directions of impulse flows).
· Source of irritation.
· Environment or energy (from source to subject).
It should be noted that human sensations are a product historical development, and in this regard they are qualitatively different from the sensations of animals. In animals, the development of sensations is entirely limited by their biological, instinctive needs. In humans, the ability to feel is not limited by biological needs. Labor created in him an incomparably wider range of needs than in animals, and in activities aimed at satisfying these needs, human abilities were constantly developing, including the ability to feel. In this regard, a person can sense a much larger number of properties of the objects around him than an animal.
Sensations are not only the source of our knowledge about the world, but also our feelings and emotions. Simplest form emotional tone is the so-called sensual, or emotional, tone of sensation, i.e. a feeling directly related to a sensation. For example, it is well known that some colors, sounds, smells can themselves, regardless of their meaning, memories and thoughts associated with them, cause us a pleasant or unpleasant feeling. The sound of a beautiful voice, the taste of alsina, the smell of roses are pleasant and have a positive emotional tone.
The creaking of a knife on glass, the smell of hydrogen sulfide, the taste of quinine are unpleasant and have a negative emotional tone.
This kind of simplest emotional conditions play a relatively insignificant role in the life of an adult, but from the point of view of the origin and development of emotions, their significance is very great.
The following functions of sensations are distinguished.
Signaling - notifying the body about vital objects or properties of the surrounding world.
Reflective (figurative) - construction of a subjective image of a property necessary for orientation in the world.
Regulatory - adaptation in the surrounding world, regulation of behavior and activity.
There are several theories of sensations.
Receptive. According to this theory, the sensory organ (receptor) passively responds to influencing stimuli. This passive response is the corresponding sensations, that is, sensation is a purely mechanical trace of external influence in the corresponding sense organ. Currently, this theory is recognized as untenable, since the active nature of sensations is denied.
Dialectical-materialistic.
According to this theory, “sensation is a real direct connection between consciousness and the external world, it is the transformation of the energy of external stimulation into a fact of consciousness” (V.L. Lenin).
Reflex.
Within the framework of the reflex concept of I.M. Sechenov and I.P. Pavlov conducted studies that showed that, according to its physiological mechanisms, sensation is an integral reflex that unites the peripheral and central sections of the analyzer through direct and feedback connections.
Sensations begin to develop immediately after birth. However, not all types of sensitivity develop equally. Immediately after birth, the child develops tactile, gustatory and olfactory sensitivity (the child reacts to the temperature of the environment, touch, pain; identifies the mother by the smell of mother's milk; distinguishes mother's milk from cow's milk or water). However, the development of these sensations continues for quite a long time (they are little developed at 4-5 years).
Visual and auditory sensations are less mature at the time of birth. Auditory sensations begin to develop faster (reacts to sound - in the first weeks of life, to direction - after two to three months, and to sound and music - in the third or fourth month). Speech hearing develops gradually. First, the child responds to the intonation of speech (in the second month), then to the rhythm, and the ability to distinguish sounds (first vowels, and then consonants) appears by the end of the first year of life.
Absolute sensitivity to light in an infant is low, but increases markedly in the first days of life. Color differentiation begins only in the fifth month.
In general, absolute sensitivity of all species reaches a high level of development in the first year of life. Relative sensitivity develops more slowly (rapid development occurs at school age).
Sensations, within certain limits, can be developed through constant training. Thanks to the possibility of developing sensations, for example, children learn (music, drawing).
Among sensory disturbances, quantitative and qualitative changes are distinguished.
Quantitative disorders include: loss or decrease in the ability to perceive various types of stimuli and an increase in this ability. Loss of sensitivity usually extends to tactile, pain, and temperature sensitivity, but can also cover all types of sensitivity.
This is usually associated with various diseases of the individual. Synesthesia is a qualitative disorder of sensations. Another type of pathology of sensations manifests itself in various unpleasant sensations: numbness, tingling, burning, crawling, etc. With various pathological diseases there may be changes in pain sensitivity. They consist of different pain sensitivity and pain tolerance.
Individual differences in sensations are a little-studied area of psychology. It is known that the sensitivity of different sense organs depends on many factors. The characteristics of the central nervous system influence (individuals with a strong nervous system have lower sensitivity); emotionality (emotional people have a more developed sense of smell); age (hearing acuity is greatest at 13 years old, visual acuity at 20-30 years old, old people hear low-frequency sounds quite well, and high-frequency sounds worse); gender (women are more sensitive to high sounds, and men - to low sounds); the nature of the activity (steelworkers distinguish the subtlest shades of a red-hot flow of metal, etc.).
2. Classification of types of sensations
There are different approaches to classifying sensations. It has long been customary to distinguish between five (based on the number of sense organs) main types of sensations: smell, taste, touch, vision and hearing. This classification of sensations according to the main modalities is correct, although not exhaustive. B.G. Ananyev spoke about eleven types of sensations. A.R. Luria believed that the classification of sensations can be carried out according to at least two basic principles - systematic and genetic (in other words, according to the principle of modality, on the one hand, and according to the principle of complexity or level of their construction, on the other).
Let's consider a systematic classification of sensations (Fig. 3). This classification was proposed by the English physiologist C. Sherrington. Considering the largest and most significant groups of sensations, he divided them into three main types: interoceptive, proprioceptive and exteroceptive sensations. The first combine signals reaching us from the internal environment of the body; the latter provide information about the position of the body in space and the position of the musculoskeletal system, ensuring the regulation of our movements; finally, still others ensure the receipt of signals from the external world and create the basis for our conscious behavior. Let's consider the main types of sensations separately.
The basis of perception are exteroceptors, since they provide an objective view of the external world.
As you know, a person has five senses. There are one more types of external sensations, since motor skills do not have a separate sensory organ, but they also cause sensations. Consequently, a person can experience six types of external sensations: visual, auditory, olfactory, tactile (tactile), gustatory and kinesthetic sensations.
Rice. 3. Systematic classification of the main types of sensations The main source of information about the external world is the visual analyzer. With its help, a person receives up to 80% of the total amount of information. The organ of visual sensation is the eye. At the level of sensations, he perceives information about light and color. Colors perceived by humans are divided into chromatic and achromatic. The first ones include the colors that make up the spectrum of the rainbow (i.e., the splitting of light - the well-known “Every hunter wants to know where the pheasant sits”). The second ones are black, white and gray colors. Color shades, containing about 150 smooth transitions from one to another, are perceived by the eye depending on the parameters of the light wave. Visual sensations have a great influence on a person. All warm colors have a positive effect on a person’s performance, excite him and cause good mood. Cool colors calm a person. Dark colors have a depressing effect on the psyche. Colors can carry warning information: red indicates danger, yellow warns, green signals safety, etc. The next most important in receiving information is the auditory analyzer. The sensations of sounds are usually divided into musical and noise. Their difference is that musical sounds are created by periodic rhythmic vibrations of sound waves, and noises are created by non-rhythmic and irregular vibrations. Auditory sensations also have great importance In human life. The source of auditory sensations is a variety of sounds acting on the organ of hearing. Auditory sensations reflect noise, musical and speech sounds. Sensations of noise and rustling signal the presence of objects and phenomena that produce sounds, their location, approach or distance. They can warn of danger and cause a certain emotional distress. Musical sensations are characterized by emotional tone and melody. These sensations are formed in a person on the basis of the education and development of musical ear and are associated with the general musical culture of human society. Speech sensations are the sensory basis speech activity person. On the basis of speech sensations, phonemic hearing is formed, thanks to which a person can distinguish and pronounce speech sounds. Phonemic hearing influences not only the development of oral and written speech, but also the acquisition of foreign language.Many people have interesting feature- a combination of sound and visual sensations into one overall sensation. In psychology, this phenomenon is called synesthesia. These are stable associations that arise between objects of auditory perception, such as melodies, and color sensations. Often people can tell “what color” a given melody or word is. Synesthesia, based on the association of color and smell, is somewhat less common. It is often characteristic of people with a developed sense of smell. Such people can be found among perfume tasters - not only a developed olfactory analyzer is important for them, but also synesthetic associations that allow Difficult language scents should be transformed into a more universal language of color. In general, the olfactory analyzer, unfortunately, is most often not very well developed in people. People like the hero of Patrick Suskind's novel “Perfume” are a rare and unique phenomenon. The sense of smell is a type of sensitivity that gives rise to the scientific sensations of smell. This is one of the most ancient, simple, but vital sensations. Anatomically, the organ of smell is located in most living creatures in the most advantageous place - in the middle, in a prominent part of the body. The path from the olfactory receptors to those brain structures where the impulses received from them are received and processed is the shortest. Nerve fibers extending from the olfactory receptors directly, without intermediate connections, enter the brain. The part of the brain called the olfactory region is also the most ancient, and the lower Living being stands on the evolutionary ladder, the more space in the mass of the brain it occupies. In fish, for example, the olfactory brain covers almost the entire surface of the hemispheres, in dogs - about one third, in humans its relative share in the volume of all brain structures is approximately one twentieth. These differences correspond to the development of other sense organs and the vital importance that this type has sensations for living beings. For some animal species, the importance of smell goes beyond the perception of smells. In insects and great apes, the sense of smell also serves as a means of intraspecific communication. The odor classification system known as the “Henning Prism” (floral, fruity, spicy, resinous, burnt, putrid) forms the corners of a prism with intermediate qualities located on the planes (Fig. 4 ).Rice. 4. “Henning Prism” There are other classifications. In practice, a comparison of a given smell with a known standard (lilac, hay, etc.) is often used. Taste sensations are a reflection of the quality of food, providing the individual with information about whether a given substance can be ingested. The sense of taste (often together with the sense of smell) is caused by the action of the chemical properties of substances dissolved in saliva or water on taste buds(taste buds) located on the surface of the tongue, the back of the pharynx, the palate and the epiglottis. The taste classification system is represented by the “Hanning Tetrahedron” (Fig. 5), in which there are four main tastes (sweet, sour, salty, bitter). Sweet Salty Fig. 5. “Hanning Tetrahedron” They are located in the corners of the tetrahedron (quadrangular pyramid), and all other taste sensations are located on the planes of the Tetrahedron and represent them as combinations of two or more basic taste sensations. Cutaneous sensitivity, or touch, is the most widely represented and widespread type of sensitivity. The familiar sensation that occurs when an object touches the surface of the skin is not an elementary tactile sensation. It is the result of a complex combination of four other, simpler types of sensations: pressure, pain, heat and cold, and for each of them there is a specific type of receptors, unevenly located in different parts of the skin surface. The presence of such receptors can be found in almost all areas of the skin. However, the specialization of skin receptors has not yet been accurately established. It is unclear whether there are receptors exclusively designed to perceive one influence, generating differentiated sensations of pressure, pain, cold or heat, or whether the quality of the resulting sensation may vary depending on the state of the same receptor, as well as on the nature of the property affecting it. It is only known that the strength and quality of skin sensations themselves are relative. For example, when simultaneously affecting the surface of one area of skin warm water its temperature is perceived differently depending on what kind of water we apply to the adjacent area of the skin. If it is cold, then on the first part of the skin there is a feeling of warmth, if it is hot, then a feeling of cold. Temperature receptors, as a rule, have two threshold values: they respond to high and low magnitude impacts, but do not respond to medium ones. Using the examples of kinesthetic sensations and feelings of balance, we can confirm the fact that not all sensations are conscious. In everyday speech that we use, there is no word that denotes sensations coming, for example, from receptors located in the muscles and working when they contract or stretch. Nevertheless, these sensations still exist, providing control of movements, assessment of the direction and speed of movement, and the magnitude of the distance. They are formed automatically, enter the brain and regulate movements at a subconscious level. To designate them in science, a word has been adopted that comes from the concept of “movement” - kinetics, and in this regard they are called kinesthetic. Without sensations of this kind, we would experience great difficulties associated with the simultaneous coordination of movements various parts body, maintaining posture, balance, controlling various involuntary movements (unconditioned reflex reactions, skills, etc.), because they all include motor moments that are performed automatically and very quickly. In addition to muscles, receptors for kinesthetic sensations are located in other organs. For example, the formation of sensations that help maintain and maintain balance occurs due to the presence of special balance receptors present in the inner ear. The feeling of acceleration or deceleration of movements depends on the work of these receptors. There is evidence that with the help of ordinary senses a person perceives stimuli that are beyond the lower threshold of his sensitivity. These stimuli (they are called subsensory) can even influence conscious sensations. This proves the existence of human sensitivity to stimuli that are not consciously felt. With the help of such sensitivity, we clarify, for example, the localization of sound. Physiologist G.V. Gershuni, in particular, writes that “immediately after a concussion, when auditory sensations are either completely absent or appear only when exposed to very strong sounds, such body responses occur as a change in the spontaneous electrical activity of the cerebral cortex - the appearance of rhythms of higher frequencies... a change in the potential difference of the skin (galvanic skin reaction) and the cochlear-pupillary reflex - a change in the diameter of the pupil under the influence of sound.” The zone of inaudible sounds that cause the cochlear-pupillary reflex was called by Gershuni the “subsensory region.” During the stages of gradual hearing restoration, this zone increases, and with complete normalization it decreases. Other involuntary reactions recorded during the pathological process behave in a similar way. Normally, the limits of the subsensory area significantly depend on the state of the person and for the cochlear-pupillary reflex range from 5 to 12 dB. The entire group of exteroceptive sensations is conventionally divided into two subgroups: contact and distant sensations. Contact sensations are caused by the direct impact of an object on the sense organs . Examples of contact sensations are taste and touch. Distant sensations reflect the qualities of objects located at some distance from the sense organs. These senses include hearing and vision. It should be noted that the sense of smell, according to many authors, occupies an intermediate position between contact and distant sensations, since formally olfactory sensations arise at a distance from the object, but at the same time, the molecules characterizing the smell of the object, with which the olfactory receptor comes into contact, undoubtedly belong to this item. This is the duality of the position occupied by the sense of smell in the classification of sensations. Since a sensation arises as a result of the influence of a certain physical stimulus on the corresponding receptor, the primary classification of sensations, which we have considered, proceeds, naturally, from the type of receptor that gives the sensation of a given quality, or “ modality." However, there are sensations that cannot be associated with any specific modality. Such sensations are called intermodal. These include, for example, vibration sensitivity, which connects the tactile-motor sphere with the auditory sphere. The sensation of vibration is sensitivity to vibrations caused by a moving body. According to most researchers, the vibration sense is an intermediate, transitional form between tactile and auditory sensitivity. In particular, some authors believe that tactile-vibration sensitivity is one of the forms of sound perception. With normal hearing, it does not appear particularly prominent, but with damage to the auditory organ, this function is clearly manifested. Vibration sensitivity takes on a special practical significance with damage to vision and hearing. It plays a big role in the lives of deaf and deaf-blind people. Deaf-blind people, thanks to the high development of vibration sensitivity, learned about the approach of a truck and other types of transport at a great distance. In the same way, through the vibrational sense, deaf-blind people recognize when someone enters their room. Consequently, sensations, being the most simple view mental processes are in fact very complex and not fully studied. Interoceptive sensations - combine signals reaching us from the internal environment of the body, sensitivity to our own metabolic processes (hunger, thirst, suffocation, etc.). Usually they are isolated at the subsensory (unconscious) subcortical level and are realized only in the case of a significant violation normal condition organism, violation of the necessary constancy of its internal environment (homeostasis). Occur thanks to receptors located on the walls of the stomach and intestines, heart and circulatory system and others internal organs. Interoceptive sensations are among the least conscious and most diffuse forms of sensations and always retain their proximity to emotional states. It should also be noted that interoceptive sensations are often called organic. Proprioceptive sensations (“deep sensitivity”) are sensations that convey information about the position of the body in space and the position of the musculoskeletal system, ensure the regulation of our movements. These sensations create the basis of human movements, playing a decisive role in their regulation. This group of sensations includes the feeling of balance, or static sensation, as well as motor, or kinesthetic, sensation. Peripheral receptors for this sensitivity are located in muscles and joints (tendons, ligaments) and are called Paccini corpuscles. Peripheral receptors for the sensation of balance are located in the semicircular canals of the inner ear. It should be noted that there are other approaches to the classification of sensations. An attempt to create a genetic classification of sensations was made by the English neurologist H. Head, who identified the more ancient - protopathic and younger - epicritic sensitivity. Protopathic sensations (Greek protos - first, primary, pathos - illness, suffering) - phylogenetically these are more ancient sensations, primitive and undifferentiated, mixed with emotions and localized. More often this concept is used in relation to skin sensitivity. This includes organic sensations (hunger, thirst, etc.). Epicritic sensations (Greek Epikrisis - judgment, decision) - phylogenetically new sensations. They are characterized by a lower threshold of irritation, the ability to sense light touches, precise localization of external irritation, and more perfect recognition of the quality of the external stimulus. (C) Information published on the siteThese include all the main types of human sensations. Types of sensations are classified according to modality, location of receptors, and contact with the stimulus. - Conclusion -
The vital role of sensations is to promptly and quickly convey to the central nervous system, as the main organ of activity control, information about the state of the external and internal environment, the presence of biologically significant factors in it.
The life of every person is complex and multifaceted. It is revealed through a number of important processes. They can be conditionally divided into social and business activity of the individual, culture, medicine, sports, communication, interpersonal relationships, scientific and research activities, entertainment and relaxation.
The full course of all the above processes is problematic, and sometimes even impossible to imagine without the involvement of all our senses. In this regard, it is necessary to evaluate the role of sensations in a person’s life, since sometimes this knowledge helps in organizing the prosperous existence of an individual in society and achieving success in a business environment.
So, sensation is the process of reflecting individual properties of objects in the objective world, both the external environment and one’s own body, arising from their direct impact on receptors (sense organs). This is a process of primary information processing, characteristic of both animals and humans. With the help of sensations, the subject reflects light, color, sounds, noises, heat, cold, smells, tastes. Sensations are a prerequisite for the creation of images and their cognition.
There are several classifications of types of sensations. According to modality (types of analyzers), sensations are distinguished: visual, auditory, tactile (tactile, temperature and pain), olfactory and gustatory. Intermodal sensations are also distinguished.
The classification of sensations based on the nature of reflection and location of receptors was presented by the English physiologist C. Sherrington. Based on the anatomical location of the receptors, sensations are divided into three classes: interoceptive (receptors are located in the internal environment of the body), proprioceptive (receptors are located in the muscles, tendons and joint capsules) and exteroceptive (receptors are located on the surface of the body). Exteroceptive ones include: contact (taste, touch) and distant (smell, hearing, vision). A.R. Luria supplements the final series with two categories: intermodal (intermediate) and non-digital types of sensations.
By origin (genetic classification by X. Head) they distinguish: protopathic and epicritic sensations.
Bibliography
1. Vygotsky L.S. Psychology. - M.: EKSMO-Press, 2000. - 1008 p.
2. Gamezo M.V., Gerasimova V.S., Mashurtseva D.A., Orlova L.M. General psychology: Educational and methodological manual. - M.: Os-89, 2007. - 352 p.
3. Gershuni G.V., Sokolov E.N. Objective changes in sensitivity and its subsensory area // Reader on sensation and perception. - M. 1975. - p. 227.
4. Glukhanyuk N.S., Semenova S.L., Pecherkina A.A. General psychology. - M.: Academic project; Ekaterinburg: Business book, 2005. - 368 p.
5. Dmitrieva N.Yu. General psychology. Summary of lectures. - M.: Eksmo, 2007. - 128 pages.
6. Itelson L.B. Lectures on general psychology. - St. Petersburg: Peter, 2004. - 320 p.
7. Leontyev A.N. Lectures on general psychology. - M.: Meaning; Ed. Center "Academy", 2007. - 511 p.
8. Lukatsky M.A., Ostrenkova M.E. Psychology. - M.: Eksmo, 2007. - 416 p.
9. Luria A.R. Lectures on general psychology. - St. Petersburg: Peter, 2004. - 320 p.
10. Maklakov A.G. General psychology: Textbook for universities. - St. Petersburg: Peter, 2008. - 583 p.
11. Maksimenko S.D. General psychology. - M.: Refl-book, 2004 - 528 p.
12. Nemov R.S. Psychology: Textbook for students. higher ᴨȇd. textbook establishments: In 3 books. - M.: VLADOS, 2003. - Book. 1: General Basics psychology. - 688.
13. General psychology: Textbook/Under general. Ed. A.V. Karpova. - M.: Gardariki, 2002. - 232 p.
14. Psychology. Textbook for humanitarian universities / Ed. V.N. Druzhinina. St. Petersburg: Peter, 2002. - 315 p.
15. Rubinshtein S.L. Fundamentals of general psychology. - St. Petersburg: Peter, 2006. - 713 p.
16. Sorokun P.A. Basics of psychology. - Pskov: PSPU, 2005 - 312 p.
The physiological basis of sensations is the activity of complex complexes of anatomical structures called analyzers. The concept of an analyzer (a device that performs the function of distinguishing external stimuli) was introduced by Academician I.P. Pavlov. He also examined the structure of the analyzers and came to the conclusion that they consist of three parts:
1) peripheral section
Called a receptor (a receptor is the perceiving part of the analyzer, a specialized nerve ending, its main function is the transformation of external energy into a nervous process);
2) nerve pathways
(afferent department - transmits excitation to the central department; efferent department - it transmits a response from the center to the periphery);
3) analyzer core– cortical sections of the analyzer (they are also called the central sections of the analyzers), in which the processing of nerve impulses coming from the peripheral sections occurs. The cortical part of each analyzer includes an area that represents a projection of the periphery (i.e., a projection of the sensory organ) in the cerebral cortex, since certain receptors correspond to certain areas of the cortex.
Thus, the organ of sensation is the central section of the analyzer.
For sensation to occur, all components of the analyzer must be used. If any part of the analyzer is destroyed, the occurrence of the corresponding sensations becomes impossible. Thus, visual sensations cease when the eyes are damaged, when the integrity of the optic nerves is damaged, and when the occipital lobes of both hemispheres are destroyed. In addition, for sensations to arise, 2 more conditions must be present:
· Sources of irritation (irritants).
· Medium or energy that is distributed in the environment from the source to the subject.
For example, in a vacuum there are no auditory sensations. In addition, the energy emitted by the source may be so small that a person does not feel it, but it can be registered by instruments. That. Energy, in order to become perceptible, must reach a certain threshold value of the analyzer system.
Also, the subject may be awake or asleep. This should also be taken into account. During sleep, the thresholds of analyzers increase significantly.
Thus, sensation is a mental phenomenon that is the result of the interaction of an energy source with the corresponding human analyzer. In this case, we mean an elementary single source of energy that creates a homogeneous sensation (of light, sound, etc.).
Five conditions must exist for sensations to occur:
· Receptors.
· Analyzer nucleus (in the cerebral cortex).
· Conducting pathways (with directions of impulse flows).
· Source of irritation.
· Environment or energy (from source to subject).
It should be noted that human sensations are a product of historical development, and therefore they are qualitatively different from the sensations of animals. In animals, the development of sensations is entirely limited by their biological, instinctive needs. In humans, the ability to feel is not limited by biological needs. Labor created in him an incomparably wider range of needs than in animals, and in activities aimed at satisfying these needs, human abilities were constantly developing, including the ability to feel. Therefore, a person can sense a much larger number of properties of the objects around him than an animal.
Sensations are not only the source of our knowledge about the world, but also our feelings and emotions. The simplest form of emotional experience is the so-called sensory, or emotional, tone of sensation, i.e. a feeling directly related to a sensation. For example, it is well known that some colors, sounds, smells can themselves, regardless of their meaning, memories and thoughts associated with them, cause us a pleasant or unpleasant feeling. The sound of a beautiful voice, the taste of an orange, the smell of a rose are pleasant and have a positive emotional tone. The creaking of a knife on glass, the smell of hydrogen sulfide, the taste of quinine are unpleasant and have a negative emotional tone. This kind of simplest emotional experiences play a relatively insignificant role in the life of an adult, but from the point of view of the origin and development of emotions, their significance is very great
The following functions of sensations are distinguished.
Signal
– notification of the body about vital objects or properties of the surrounding world.
Reflective (shaped)
– construction of a subjective image of a property necessary for orientation in the world.
Regulatory
– adaptation in the surrounding world, regulation of behavior and activity.
There are several theories of sensations.
Receptive.
According to this theory, the sensory organ (receptor) passively responds to stimuli. This passive response is the corresponding sensations, that is, a sensation is a purely mechanical imprint of an external influence in the corresponding sense organ. Currently, this theory is recognized as untenable, since the active nature of sensations is denied.
Dialectical-materialistic. According to this theory, “sensation is a real direct connection between consciousness and the external world, it is the transformation of the energy of external stimulation into a fact of consciousness” (V.L. Lenin).
Reflex. Within the framework of the reflex concept of I.M. Sechenov and I.P. Pavlov conducted studies that showed that, according to its physiological mechanisms, sensation is an integral reflex that unites the peripheral and central sections of the analyzer through direct and feedback connections.
Sensations begin to develop immediately after birth. However, not all types of sensitivity develop equally. Immediately after birth, the child develops tactile, gustatory and olfactory sensitivity (the child reacts to environmental temperature, touch, pain; identifies the mother by the smell of mother’s milk; distinguishes mother’s milk from cow’s milk or water). However, the development of these sensations continues for quite a long time (they are little developed at 4–5 years).
Visual and auditory sensations are less mature at the time of birth. Auditory sensations begin to develop faster (reacts to sound - in the first weeks of life, to direction - after two to three months, and to singing and music - in the third or fourth month). Speech hearing develops gradually. First, the child reacts to the intonation of speech (in the second month), then to the rhythm, and the ability to distinguish sounds (first vowels, and then consonants) appears by the end of the first year of life.
Absolute sensitivity to light in an infant is low, but increases markedly in the first days of life. Color differentiation begins only in the fifth month.
In general, absolute sensitivity of all species reaches a high level of development in the first year of life. Relative sensitivity develops more slowly (rapid development occurs at school age).
Sensations, within certain limits, can be developed through constant training. Thanks to the possibility of developing sensations, for example, children learn (music, drawing).
Among sensory disturbances, quantitative and qualitative changes are distinguished.
Quantitative disorders include: loss or decrease in the ability to perceive various types of stimuli and an increase in this ability. Loss of sensitivity usually extends to tactile, pain, and temperature sensitivity, but can also cover all types of sensitivity.
This is usually associated with various diseases of the individual. Synesthesia is a qualitative disorder of sensations. Another type of pathology of sensations manifests itself in various unpleasant sensations: numbness, tingling, burning, crawling, etc. With various pathological diseases there may be changes in pain sensitivity. They consist of different pain sensitivity and pain tolerance.
Individual differences in sensations are a little-studied area of psychology. It is known that the sensitivity of different sense organs depends on many factors. The characteristics of the central nervous system influence (individuals with a strong nervous system have lower sensitivity); emotionality (emotional people have a more developed sense of smell); age (hearing acuity is greatest at 13 years old, visual acuity at 20–30 years old, old people hear low-frequency sounds quite well, and high-frequency sounds worse); gender (women are more sensitive to high sounds, and men are more sensitive to low sounds); nature of the activity (steelworkers distinguish the subtlest shades of a red-hot flow of metal, etc.)
The physiological basis of sensation has been deeply and systematically studied within the framework of the reflex concept of I. M. Sechenov and I. P. Pavlov. It has been shown that, in essence, sensation is a holistic reflex that unites the peripheral and central parts of the nervous system. I. P. Pavlov introduced the concept of “analyzer” and showed that the activity of analyzers reveals physiological mechanism the occurrence of sensations.
ANALYZER - a nervous formation that carries out the perception, analysis and synthesis of active
on the body from external and internal stimuli.
The analyzer consists of 3 blocks:
- 1). The receptor is a peripheral part of the analyzer that performs the function of receiving information from stimuli acting on the body. RECEPTOR - a specialized cell designed to perceive a specific stimulus from the external or internal environment and to convert its energy from a physical or chemical form into the form of nervous excitation (impulse).
- 2). Afferent (conducting) and efferent (outgoing) pathways. Afferent pathways are areas of the nervous system through which the resulting excitation enters the central nervous system. Efferent pathways are areas along which the response impulse (based on information processed in the central nervous system) is transmitted to the receptors, determining their motor activity (reaction to the stimulus).
- 3). Cortical projection zones (central section of the analyzer) are areas of the cerebral cortex in which nerve impulses received from receptors are processed. Each analyzer in the cerebral cortex has its own “representation” (projection), where the analysis and synthesis of information of a certain sensitivity (sensory modality) occurs.
Depending on the type of sensitivity, visual, auditory, olfactory, gustatory, skin, motor and other analyzers are distinguished. Each analyzer singles out stimuli of only a certain type from the entire variety of influences. For example, a hearing analyzer identifies waves generated by vibrations of air particles. The taste analyzer generates an impulse as a result of “chemical analysis” of molecules dissolved in saliva, and the olfactory analyzer generates an impulse in the air. The visual analyzer perceives electromagnetic waves, the characteristics of which give rise to a particular visual image.
The conscious experience of a sensation occurs not during the perception of the stimulus by the receptor, but after the receipt and processing of information in the brain. Therefore, sensation as a mental phenomenon arises at the level of brain activity. When exposed to an irritant, we are talking about the physical process of irritation; during the formation and transmission of impulses they speak of excitation as a physiological process.
The physiological basis of sensations is the activity of complex complexes of anatomical structures, called Pavlov's analyzers; each analyzer consists of 3 parts. 1. peripheral section - receptors. Receptor – the perceiving part of the analyzer, its main function is to transform external energy into a nerve impulse. 2. conducting nerve pathways - (centripetal, centrifugal, afferent) 3. cortical sections of the analyzer, in which the processing of nerve impulses coming from peripheral sections occurs. For sensation to arise, it is necessary to use all the components of the analyzer. If any part of the analyzer is destroyed, the occurrence of sensation becomes impossible (visual sensation stops if the eye is damaged.) Analyzer- an active organ that reflexively rearranges itself under the influence of stimuli, so sensation is not a passive process, but always includes motor components. Thus, the American psychologist Neff, observing areas of the skin with a microscope, became convinced that when they are irritated with a needle, the moment the sensation occurs is accompanied by a reflex-motor reaction of this area of the skin.
12 Classification of sensations
There are different approaches to the classification of sensations. It has long been customary to distinguish 5 main types (based on the number of sense organs): smell, taste, touch, vision, hearing. This classification according to its main modalities is correct, although not exhaustive. For example, Ananyev spoke about 11 types of sensations. Luria believes that the classification of sensations can be carried out according to at least two basic principles: systematic, genetic (by the principle of modality on the one hand and by the principle of complexity or level of their structure on the other hand). A systematic classification was proposed by English physiologists Sherrington. SYSTEMATIC Classification of the main types of sensations Exteroceptive– are the largest group . sensations. They bring it to people's attention. information from the outside world and are the main group. sensations that connect people. with the external environment. Whole gr. These sensations are conventionally divided into 2 subgroups. contact and remote. Contact – are caused directly by the impact of an object on the senses. Contact are taste and touch. Distant – reflect the quality of an object that is located at a certain distance from the senses. These sensations include hearing and vision. It should be noted that the sense of smell, according to many authors, occupies an intermediate position between contact and distant ones, since formally the olfactory sensation occurs at a distance from the object, but at the same time the molecules characterizing the smell of the object with which the olfactory receptor is in contact , undoubtedly belong to this subject. This is the duality of the position that marks the olfactory sensation. Since sensation arises as a result of the action of a certain physical stimulus on the corresponding receptor, the primary classification of sensations comes, naturally, from the receptor that gives sensations of a given quality or modality. INTEROCEPTIVE– organic (sensation of pain) - combine signals that reach us from the internal processes of the body, arise thanks to receptors that are located on the walls of the stomach and intestines, heart and blood vessels, and other internal organs. Receptors that perceive information about the state of internal organs are called internal receptors. PROPRIOCEPTIVE – transmit signals about the position of the body in space and form the afferent basis of human movements. They play a decisive role in their regulation. The described group of sensations includes the sensation of balance (stomatic sensations) and movement (kinesthetic sensations). Receptors for these sensations are located in muscles, joints, tendons and are called Paccini corpuscles. Peripheral receptors of this group. sensations are located in the semicircular canals of the inner ear, which are responsible for balance. In addition to systematic, there is genetic classification. It was suggested by the English neuropathologist Head. Genetic classification allows us to distinguish 2 types of sensitivity: protatapic– which includes organic feelings: thirst, hunger, etc. epicritic– main types of sensations.