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Conditioned reflexes in humans are formed in the process. Reflex - example

The term “reflex” was introduced by the French scientist R. Descartes in the 17th century. But to explain mental activity it was used by the founder of Russian materialistic physiology I.M. Sechenov. Developing the teachings of I.M. Sechenov. I. P. Pavlov experimentally studied the peculiarities of the functioning of reflexes and used the conditioned reflex as a method for studying higher nervous activity.

He divided all reflexes into two groups:

unconditional;
conditional.

Unconditioned reflexes

Unconditioned reflexes- innate reactions of the body to vital stimuli (food, danger, etc.).

They do not require any conditions for their production (for example, the release of saliva at the sight of food). Unconditioned reflexes are a natural reserve of ready-made, stereotypical reactions of the body. They arose as a result of the long evolutionary development of this animal species. Unconditioned reflexes are the same in all individuals of the same species. They are carried out using the spinal and lower departments brain. Complex complexes unconditioned reflexes manifest themselves in the form of instincts.

Rice. 14. The location of some functional zones in the human cerebral cortex: 1 - zone of speech production (Broca's center), 2 - area of the motor analyzer, 3 - area of analysis of oral verbal signals (Wernicke's center), 4 - area of the auditory analyzer, 5 - analysis of written verbal signals, 6 - visual analyzer area

Conditioned reflexes

But the behavior of higher animals is characterized not only by innate, i.e., unconditioned reactions, but also by such reactions that are acquired by a given organism in the process of individual life activity, i.e. conditioned reflexes. The biological meaning of the conditioned reflex is that numerous external stimuli surrounding the animal in natural conditions and in themselves not of vital importance, preceding in the animal’s experience food or danger, the satisfaction of other biological needs, begin to act as signals, by which the animal orients its behavior (Fig. 15).

So, the mechanism of hereditary adaptation is an unconditioned reflex, and the mechanism of individual variable adaptation is conditioned reflex produced when combining vital significant events with accompanying signals.

Rice. 15. Scheme of formation of a conditioned reflex

a - salivation is caused by an unconditioned stimulus - food;
b - excitation from a food stimulus is associated with a previous indifferent stimulus (light bulb);
c - the light of the light bulb became a signal of the possible appearance of food: a conditioned reflex was developed to it

A conditioned reflex is developed on the basis of any of the unconditioned reactions. Reflexes to unusual signals that do not occur in a natural environment are called artificial conditioned. In laboratory conditions, it is possible to develop many conditioned reflexes to any artificial stimulus.

I. P. Pavlov associated with the concept of a conditioned reflex principle of signaling of higher nervous activity, the principle of synthesis of external influences and internal states.

Pavlov's discovery of the basic mechanism of higher nervous activity - the conditioned reflex - became one of the revolutionary achievements of natural science, a historical turning point in the understanding of the connection between the physiological and the mental.

Understanding the dynamics of formation and changes in conditioned reflexes began the discovery of complex mechanisms of human brain activity and the identification of patterns of higher nervous activity.

Conditioned reflex- this is an acquired reflex characteristic of an individual (individual). They arise during the life of an individual and are not fixed genetically (not inherited). They appear under certain conditions and disappear in their absence. They are formed on the basis of unconditioned reflexes with the participation of higher parts of the brain. Conditioned reflex reactions depend on past experience, on the specific conditions in which the conditioned reflex is formed.

The study of conditioned reflexes is associated primarily with the name of I. P. Pavlov and the students of his school. They showed that a new conditioned stimulus can trigger a reflex response if it is presented for some time together with an unconditioned stimulus. For example, if a dog is allowed to sniff meat, then gastric juice is released (this is an unconditioned reflex). If, simultaneously with the appearance of meat, a bell rings, then the dog’s nervous system associates this sound with food, and gastric juice will be released in response to the bell, even if the meat is not presented. This phenomenon was discovered independently by Edwin Twitmyer at approximately the same time as in the laboratory of I. P. Pavlov. Conditioned reflexes are the basis acquired behavior. This is the most simple programs. The world is constantly changing, so only those who quickly and expediently respond to these changes can live successfully in it. As we gain life experience, a system of conditioned reflex connections develops in the cerebral cortex. Such a system is called dynamic stereotype. It underlies many habits and skills. For example, having learned to skate or bicycle, we subsequently no longer think about how we should move so as not to fall.

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Human Anatomy: Conditioned Reflexes

Conditioned reflexes

Higher nervous activity

Subtitles

Formation of a conditioned reflex

To do this you need:

The presence of 2 stimuli: an unconditioned stimulus and an indifferent (neutral) stimulus, which then becomes a conditioned signal;
Certain strength of stimuli. The unconditioned stimulus must be so strong as to cause dominant excitation in the central nervous system. The indifferent stimulus must be familiar so as not to cause a pronounced orienting reflex.
A repeated combination of stimuli over time, with the indifferent stimulus acting first, then the unconditioned stimulus. IN further action 2 stimuli continue and end simultaneously. A conditioned reflex will occur if an indifferent stimulus becomes a conditioned stimulus, that is, it signals the action of an unconditioned stimulus.
Constancy environment- the development of a conditioned reflex requires constancy of the properties of the conditioned signal.

The mechanism of formation of conditioned reflexes

At action of an indifferent stimulus excitation occurs in the corresponding receptors, and impulses from them enter the brain section of the analyzer. When exposed to an unconditioned stimulus, specific excitation of the corresponding receptors occurs, and impulses through the subcortical centers go to the cerebral cortex (cortical representation of the center of the unconditioned reflex, which is the dominant focus). Thus, two foci of excitation simultaneously arise in the cerebral cortex: In the cerebral cortex, a temporary reflex connection is formed between two foci of excitation according to the dominant principle. When a temporary connection occurs, the isolated action of a conditioned stimulus causes an unconditioned reaction. In accordance with Pavlov's theory, the consolidation of temporary reflex communication occurs at the level of the cerebral cortex, and it is based on the principle of dominance.

Types of conditioned reflexes

There are many classifications of conditioned reflexes:

If the classification is based on unconditioned reflexes, then we distinguish between food, protective, orientation, etc.
If the classification is based on the receptors on which the stimuli act, exteroceptive, interoceptive and proprioceptive conditioned reflexes are distinguished.
Depending on the structure of the used conditioned stimulus, simple and complex (complex) conditioned reflexes are distinguished.
In real conditions of the functioning of the body, as a rule, the conditioned signals are not individual, single stimuli, but their temporal and spatial complexes. And then the conditioned stimulus is a complex of environmental signals.
There are conditioned reflexes of the first, second, third, etc. order. When a conditioned stimulus is reinforced by an unconditioned one, a first-order conditioned reflex is formed. A second-order conditioned reflex is formed if a conditioned stimulus is reinforced by a conditioned stimulus to which a conditioned reflex was previously developed.
Natural reflexes are formed in response to stimuli that are natural, accompanying properties of the unconditional stimulus on the basis of which they are developed. Natural conditioned reflexes, compared to artificial ones, are easier to form and more durable.

Notes

Ivan Petrovich Pavlov's school conducted vivisector experiments not only on dogs, but also on people. Street children aged 6–15 years were used as laboratory material. These were tough experiments, but they were the ones that made it possible to understand the nature of human thinking. These experiments were carried out in the children's clinic of the 1st LMI, in the Filatov hospital, in the hospital named after. Rauchfus, in the Department of Experimental Pediatrics of the IEM, as well as in several orphanages. are essential information. In two works by N. I. Krasnogorsky, “Development of the doctrine of the physiological activity of the brain in children” (L., 1939) and “Higher nervous activity of the child” (L., 1958), Professor Mayorov, who was the official chronicler of the Pavlovian school, melancholy noted: “ Some of our employees expanded the range of experimental objects and began studying conditioned reflexes in other animal species; in fish, ascidians, birds, lower apes, as well as children" (F. P. Mayorov, "History of the doctrine of conditioned reflexes." M., 1954). "laboratory material" of a group of Pavlov's students (Prof. N. I. Krasnogorsky , A.G. Ivanov-Smolensky, I. Balakirev, M.M. Koltsova, I. Kanaev) became homeless children. Full understanding at all levels was ensured by the Cheka.A. A. Yushchenko in his work “Conditioned Reflexes of a Child” (1928 All this is confirmed by protocols, photographs and documentary film“Mechanics of the Brain” (another title is “Animal and Human Behavior”; directed by V. Pudovkin, camera by A. Golovnya, produced by the Mezhrabprom-Rus film factory, 1926)

Reflex– the body’s response is not an external or internal irritation, carried out and controlled by the central nervous system. The development of ideas about human behavior, which has always been a mystery, was achieved in the works of Russian scientists I. P. Pavlov and I. M. Sechenov.

Reflexes unconditioned and conditioned.

Unconditioned reflexes- These are innate reflexes that are inherited by offspring from their parents and persist throughout a person’s life. The arcs of unconditioned reflexes pass through the spinal cord or brain stem. The cerebral cortex is not involved in their formation. Unconditioned reflexes ensure the organism's adaptation only to those changes in the environment that have often been encountered by many generations of a given species.

TO unconditioned reflexes relate:

Food (salivation, sucking, swallowing);
Defensive (coughing, sneezing, blinking, withdrawing your hand from a hot object);
Indicative (squinting eyes, turning the head);
Sexual (reflexes associated with reproduction and care of offspring).
The importance of unconditioned reflexes lies in the fact that thanks to them the integrity of the body is preserved, maintaining constancy internal environment and reproduction occurs. Already in a newborn child the simplest unconditioned reflexes are observed.
The most important of these is the sucking reflex. The stimulus of the sucking reflex is the touching of an object to the child’s lips (mother’s breast, pacifier, toy, finger). The sucking reflex is an unconditioned food reflex. In addition, the newborn already has some protective unconditioned reflexes: blinking, which occurs if a foreign body approaches the eye or touches the cornea, constriction of the pupil when exposed to strong light on the eyes.

Particularly pronounced unconditioned reflexes in various animals. Not only individual reflexes can be innate, but also more complex forms of behavior, which are called instincts.

Conditioned reflexes– these are reflexes that are easily acquired by the body throughout life and are formed on the basis of an unconditioned reflex under the action of a conditioned stimulus (light, knock, time, etc.). I.P. Pavlov studied the formation of conditioned reflexes in dogs and developed a method for obtaining them. To develop a conditioned reflex, a stimulus is needed - a signal that triggers the conditioned reflex; repeated repetition of the action of the stimulus allows you to develop a conditioned reflex. During the formation of conditioned reflexes, a temporary connection arises between the centers of the analyzers and the centers of the unconditioned reflex. Now this unconditioned reflex is not carried out under the influence of completely new external signals. These irritations from the surrounding world, to which we were indifferent, can now become vitally important. Throughout life, many conditioned reflexes are developed that form the basis of our life experience. But this vital experience has meaning only for a given individual and is not inherited by its descendants.

In a separate category conditioned reflexes distinguish motor conditioned reflexes developed during our lives, i.e. skills or automated actions. The meaning of these conditioned reflexes is to master new motor skills and develop new forms of movements. During his life, a person masters many special motor skills related to his profession. Skills are the basis of our behavior. Consciousness, thinking, attention are freed from performing those operations that have become automated and become skills Everyday life. The most successful way to master skills is through systematic exercises, correcting errors noticed in time, and knowing the ultimate goal of each exercise.

If you do not reinforce the conditioned stimulus with the unconditioned stimulus for some time, then inhibition of the conditioned stimulus occurs. But it doesn't disappear completely. When the experience is repeated, the reflex is restored very quickly. Inhibition is also observed when exposed to another stimulus of greater strength.

8. The individuality of conditioned reflexes is manifested in the fact that 1) an individual inherits only certain conditioned reflexes 2) each individual of the same species has its own life experience 3) they are formed on the basis of individual unconditioned reflexes 4) each individual has an individual mechanism for the formation of a conditioned reflex

20-09-2010 15:22
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Answers (1) Alinka Konkova +1 09/20/2010 20:02

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What are unconditioned reflexes?

An unconditioned reflex is an innate, stereotypical reaction of the body to the influence of the internal or environmental environment, inherited by the offspring from the parents. It remains in a person throughout his life. Reflex arcs pass through the brain and the cerebral cortex does not take part in their formation. The significance of the unconditioned reflex is that it ensures the adaptation of the human body directly to those environmental changes that often accompanied many generations of his ancestors.

What reflexes are unconditioned?

The unconditioned reflex is the main form of activity nervous system, automatic reaction to a stimulus. And since a person is influenced various factors, then there are different reflexes: food, defensive, orientation, sexual... Food ones include salivation, swallowing and sucking. Defensive actions include coughing, blinking, sneezing, and jerking limbs away from hot objects. Approximate reactions can be called turning the head, squinting the eyes. Sexual instincts include those associated with reproduction, as well as caring for offspring. The significance of the unconditioned reflex is that it ensures the preservation of the integrity of the body and maintains the constancy of the internal environment. Thanks to him, reproduction occurs. Even in newborn children, one can observe an elementary unconditioned reflex - this is sucking. By the way, it is the most important. Irritant in in this case touching the lips of any object (pacifier, mother's breast, toy or finger). Another important unconditioned reflex is blinking, which occurs when a foreign body approaches the eye or touches the cornea. This reaction belongs to the protective or defensive group. Also observed in children, for example, when exposed to strong light. However, the signs of unconditioned reflexes are most clearly manifested in various animals.

What are conditioned reflexes?

Conditioned reflexes are those acquired by the body during life. They are formed on the basis of inherited ones, subject to exposure to an external stimulus (time, knocking, light, and so on). A striking example is the experiments conducted on dogs by academician I.P. Pavlov. He studied the formation of this type of reflexes in animals and was the developer of a unique method for obtaining them. So, to develop such reactions, the presence of a regular stimulus - a signal - is necessary. It triggers the mechanism, and repeated repetition of the stimulus allows it to develop. In this case, a so-called temporary connection arises between the arcs of the unconditioned reflex and the centers of the analyzers. Now the basic instinct awakens under the influence of fundamentally new external signals. These stimuli from the surrounding world, to which the body was previously indifferent, begin to acquire exceptional, vital importance. Each living creature can develop many different conditioned reflexes during its life, which form the basis of its experience. However, this applies only to this particular individual; this life experience will not be inherited.

An independent category of conditioned reflexes

It is customary to classify into a separate category conditioned reflexes of a motor nature developed throughout life, that is, skills or automated actions. Their meaning is to master new skills, as well as develop new motor forms. For example, over the entire period of his life a person masters many special motor skills that are associated with his profession. They are the basis of our behavior. Thinking, attention, and consciousness are freed up when performing operations that have reached automaticity and become a reality of everyday life. The most successful way to master skills is to systematically perform the exercise, timely correction of noticed errors, and knowledge of the ultimate goal of any task. If the conditioned stimulus is not reinforced by the unconditioned stimulus for some time, it is inhibited. However, it does not disappear completely. If you repeat the action after some time, the reflex will be restored fairly quickly. Inhibition can also occur when a stimulus of even greater strength appears.

Compare unconditioned and conditioned reflexes

As mentioned above, these reactions differ in the nature of their occurrence and have different formation mechanisms. In order to understand what the difference is, just compare unconditioned and conditioned reflexes. Thus, the first ones are present in a living creature from birth; throughout life they do not change or disappear. In addition, unconditioned reflexes are the same in all organisms of a particular species. Their significance lies in preparing a living being for constant conditions. The reflex arc of this reaction passes through the brain stem or spinal cord. As an example, here are some (congenital): active secretion of saliva when a lemon enters the mouth; sucking movement of the newborn; coughing, sneezing, withdrawing hands from a hot object. Now let's look at the characteristics of conditioned reactions. They are acquired throughout life, can change or disappear, and, no less important, each organism has its own individual (its own). Their main function is to adapt a living creature to changing conditions. Their temporary connection (reflex centers) is created in the cerebral cortex. An example of a conditioned reflex is the reaction of an animal to a nickname or the reaction of a six-month-old child to a bottle of milk.

Unconditioned reflex diagram

According to the research of academician I.P. Pavlova, general scheme unconditioned reflexes is as follows. Certain receptor nerve devices are affected by certain stimuli from the internal or external world of the body. As a result, the resulting irritation transforms the entire process into the so-called phenomenon of nervous excitation. It is transmitted along nerve fibers (as if through wires) to the central nervous system, and from there it goes to a specific working organ, already turning into a specific process at the cellular level of a given part of the body. It turns out that certain stimuli are naturally connected with this or that activity in the same way as cause and effect.

Features of unconditioned reflexes

The characteristics of unconditioned reflexes presented below systematize the material presented above; it will help to finally understand the phenomenon we are considering. So, what are the features of inherited reactions?

Unconditioned instinct and reflex of animals

The exceptional constancy of the nervous connection underlying unconditional instinct is explained by the fact that all animals are born with a nervous system. She is already able to respond appropriately to specific environmental stimuli. For example, a creature may flinch at a sharp sound; he will secrete digestive juice and saliva when food enters his mouth or stomach; it will blink when visually stimulated, and so on. Innate in animals and humans are not only individual unconditioned reflexes, but also much more complex forms of reactions. They are called instincts.

An unconditioned reflex, in fact, is not a completely monotonous, template, transfer reaction of an animal to an external stimulus. It is characterized, although elementary, primitive, but still by variability, variability, depending on external conditions (strength, peculiarities of the situation, position of the stimulus). In addition, it is influenced by the internal states of the animal (decreased or increased activity, pose and others). So, also I.M. Sechenov, in his experiments with decapitated (spinal) frogs, showed that when exposed to the fingers hind legs In this amphibian, the opposite motor reaction occurs. From this we can conclude that the unconditioned reflex still has adaptive variability, but within insignificant limits. As a result, we find that the balancing of the organism and the external environment achieved with the help of these reactions can be relatively perfect only in relation to slightly changing factors of the surrounding world. The unconditioned reflex is not able to ensure the animal’s adaptation to new or sharply changing conditions.

As for instincts, sometimes they are expressed in the form of simple actions. For example, the rider, thanks to his sense of smell, finds the larvae of another insect under the bark. It pierces the bark and lays its egg in the found victim. This ends all of its actions that ensure continuation of the family. There are also complex unconditioned reflexes. Instincts of this kind consist of a chain of actions, the totality of which ensures procreation. Examples include birds, ants, bees and other animals.

Species specificity

Unconditioned reflexes (specific) are present in both humans and animals. It should be understood that such reactions will be the same in all representatives of the same species. An example is a turtle. All species of these amphibians retract their heads and limbs into their shell when danger arises. And all the hedgehogs jump and make a hissing sound. In addition, you should know that not all unconditioned reflexes occur at the same time. These reactions vary with age and season. For example, the breeding season or the motor and sucking actions that appear in an 18-week fetus. Thus, unconditioned reactions are a kind of development for conditioned reflexes in humans and animals. For example, as cubs grow older, they transition into the category of synthetic complexes. They increase the body's adaptability to external conditions environment.

Unconditional inhibition

In the process of life, each organism is regularly exposed - both from the outside and from the inside - to various stimuli. Each of them is capable of causing a corresponding reaction - a reflex. If all of them could be realized, then the life activity of such an organism would become chaotic. However, this does not happen. On the contrary, reactionary activity is characterized by consistency and orderliness. This is explained by the fact that unconditioned reflexes are inhibited in the body. This means that the most important reflex at a particular moment in time delays the secondary ones. Typically, external inhibition can occur at the moment of starting another activity. The new pathogen, being stronger, leads to the attenuation of the old one. And as a result, the previous activity will automatically stop. For example, a dog is eating, and at that moment the doorbell rings. The animal immediately stops eating and runs to meet the newcomer. Occurs abrupt change activity, and the dog’s salivation stops at this moment. Unconditional inhibition of reflexes also includes some innate reactions. In them, certain pathogens cause the complete cessation of certain actions. For example, the anxious clucking of a hen makes the chicks freeze and hug the ground, and the onset of darkness forces the canary to stop singing.

In addition, there is also a protective It arises as a response to a very strong stimulus that requires the body to take actions that exceed its capabilities. The level of such influence is determined by the frequency of impulses of the nervous system. The more excited a neuron is, the higher the frequency of the stream of nerve impulses it generates. However, if this flow exceeds certain limits, then a process will arise that will begin to interfere with the passage of excitation through the neural circuit. The flow of impulses along the reflex arc of the spinal cord and brain is interrupted, resulting in inhibition that preserves executive bodies from complete exhaustion. What conclusion follows from this? Thanks to the inhibition of unconditioned reflexes, the body selects from all possible options the most adequate one, capable of protecting against excessive activity. This process also contributes to the exercise of so-called biological precautions.

Reflex- this is the body’s response to irritation from the external or internal environment, carried out with the help of the central nervous system. There are unconditioned and conditioned reflexes.

Unconditioned reflexes- these are congenital, permanent, hereditarily transmitted reactions characteristic of representatives of a given type of organism. For example, pupillary, knee, Achilles and other reflexes. Unconditioned reflexes ensure the interaction of the organism with the external environment, its adaptation to environmental conditions and create conditions for the integrity of the organism. Unconditioned reflexes arise immediately after the action of a stimulus, since they are carried out according to ready-made, inherited, reflex arcs, which are always constant. Complex unconditioned reflexes are called instincts.
Unconditioned reflexes include sucking and motor reflexes, which are already characteristic of an 18-week fetus. Unconditioned reflexes are the basis for the development of conditioned reflexes in animals and humans. In children, with age, they turn into synthetic complexes of reflexes, which increases the body’s adaptability to external environment.

Conditioned reflexes- reactions are adaptive, temporary and strictly individual. They are inherent only in one or several representatives of the species, subjected to training (training) or influence natural environment. Conditioned reflexes are developed gradually, in the presence of a certain environment, and are a function of the normal, mature cortex of the cerebral hemispheres and lower parts of the brain. In this regard, conditioned reflexes are related to unconditioned ones, since they are a response of the same material substrate - nervous tissue.

If the conditions for the development of reflexes are constant from generation to generation, then the reflexes can become hereditary, that is, they can turn into unconditioned. An example of such a reflex is the opening of the beak of blind and fledgling chicks in response to the shaking of the nest by a bird flying in to feed them. Since shaking the nest is followed by feeding, which was repeated in all generations, the conditioned reflex becomes unconditioned. However, all conditioned reflexes are adaptive reactions to a new external environment. They disappear when the cerebral cortex is removed. Higher mammals and humans with damage to the cortex become deeply disabled and die in the absence of the necessary care.

Numerous experiments conducted by I.P. Pavlov showed that the basis for the development of conditioned reflexes is formed by impulses arriving along afferent fibers from extero- or interoreceptors. For their formation it is necessary following conditions: 1) the action of an indifferent (in the future conditioned) stimulus must precede the action of an unconditioned stimulus. With a different sequence, the reflex is not developed or is very weak and quickly fades away; 2) for a certain time, the action of the conditioned stimulus must be combined with the action of the unconditioned stimulus, that is, the conditioned stimulus is reinforced by the unconditioned. This combination of stimuli should be repeated several times. Besides, prerequisite When developing a conditioned reflex, there is a normal function of the cerebral cortex, the absence of painful processes in the body and extraneous stimuli.
Otherwise, in addition to the reinforced reflex being developed, an indicative or reflex of the internal organs (intestines, bladder, etc.) will also occur.

An active conditioned stimulus always causes a weak focus of excitation in the corresponding area of the cerebral cortex. The unconditioned stimulus that is connected (after 1-5 s) creates a second, stronger focus of excitation in the corresponding subcortical nuclei and the area of the cerebral cortex, which distracts the impulses of the first (conditioned) weaker stimulus. As a result, a temporary connection is established between both foci of excitation of the cerebral cortex. With each repetition (i.e. reinforcement), this connection becomes stronger. The conditioned stimulus turns into a conditioned reflex signal. To develop a conditioned reflex, a conditioned stimulus of sufficient strength and high excitability of the cells of the cerebral cortex are required, which must be free from external stimuli. Compliance with the above conditions accelerates the development of a conditioned reflex.

Depending on the method of development, conditioned reflexes are divided into secretory, motor, vascular, reflexes of changes in internal organs etc.

A reflex developed by reinforcing a conditioned stimulus with an unconditioned one is called a first-order conditioned reflex. Based on it, you can develop a new reflex. For example, by combining a light signal with feeding, a dog has developed a strong conditioned salivation reflex. If you give a bell (sound stimulus) before the light signal, then after several repetitions of this combination the dog begins to salivate in response to the sound signal. This will be a second-order reflex, or secondary, reinforced not by an unconditioned stimulus, but by a first-order conditioned reflex. When developing conditioned reflexes of higher orders, it is necessary that a new indifferent stimulus is turned on 10-15 s before the onset of the conditioned stimulus of a previously developed reflex. If the stimulus acts at intervals that are closer or combined, then a new reflex will not appear, and the previously developed one will fade away, as inhibition will develop in the cerebral cortex. Repeated repetition of jointly acting stimuli or a significant overlap of the time of action of one stimulus on another causes the appearance of a reflex to a complex stimulus.

A certain period of time can also become a conditioned stimulus for developing a reflex. People have a temporary reflex to feel hungry during the hours when they usually eat. Intervals can be quite short. In children school age reflex for time - weakening of attention before the end of the lesson (1-1.5 minutes before the bell). This is the result not only of fatigue, but also of the rhythmic work of the brain during training sessions. The reaction to time in the body is the rhythm of many periodically changing processes, for example, breathing, cardiac activity, awakening from sleep or hibernation, molting of animals, etc. Its occurrence is based on the rhythmic sending of impulses from the corresponding organs to the brain and back to the effector organs devices.

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