galvanic response. Method for registration of galvanic skin reactions and device for its implementation
Skin-galvanic reaction(GSR) is a bioelectric reaction recorded from the surface of the skin. Synonyms: psychogalvanic reflex, electrical activity of the skin (EAK). GSR is considered as a component of the orienting reflex, defensive, emotional and other reactions of the body associated with sympathetic innervation, mobilization of adaptive-trophic resources, etc., and is the result of the activity of the sweat glands. GSR can be recorded from any part of the skin, but best of all - from the fingers and hands, soles of the feet.
The widespread use of GSR for research and practical purposes was initiated by the French neuropathologist K. Feret, who discovered that when a weak current is passed through the forearm, changes in the electrical resistance of the skin occur (1888), and the Russian physiologist I. R. Tarkhanov (Tarkhnishvili, Tarkhan-Mouravi) , who discovered the skin potential and its change during internal experiences, as well as in response to sensory stimulation (1889). These discoveries formed the basis of two main methods for recording GSR - exosomatic (measurement of skin resistance) and endosomatic (measurement of electrical potentials of the skin itself). Later it turned out that the methods of Feret and Tarkhanov give different results.
K. Jung and F. Peterson (1907) were among the first to show the relationship between GSR and the degree of emotional experience. In GSR, Jung saw an objective physiological "window" into unconscious processes. GSR is one of the most common indicators, due to the ease of its registration and measurement. It is successfully used to control the state of a person when performing various types of activities (diagnosing a functional state), in studies of the emotional-volitional sphere and intellectual activity; is one of the indicators in lie detection. Quite interesting and varied facts were found: a more pronounced increase in GSR in response to more ridiculous jokes (E. Linde); correspondence of GSR peaks to stressful episodes of the film (R. Lazarus et al.); a more significant increase in the electrical conductivity of the skin with the emotion of fear than with the emotion of anger (E. Ex); an increase in GSR during the perception of obscene words (E. McGuinness), etc. All these facts indicate a high sensitivity of GSR indicators. At one time, GSR was seen as something like a universal key to almost all psychological problems (the “magic of objectivity” and the simplistic idea that emotional states can be described using only one parameter, namely arousal, played a role here), but this turned out to be another scientific utopia. The limited possibilities of the GSR as a psychophysiological indicator are evidenced, in particular, by the data of G. Jones (1950) that, within certain limits, there is an inverse relationship between the magnitude of the GSR and the excitation manifested in behavior. In addition, studies on advertising effectiveness have found that GSR scores in ad perceptions are far from unambiguously associated with behavioral responses.
Recently, many psychophysiologists oppose the very term "GSR" and replace it with the more accurate "EAK" ( skin electrical activity), which combines a number of indicators that vary depending on the nature of the stimulus and the internal state of the subject. EAK indicators include skin potential level (SPL, or SPL), skin potential response (RPK, or SPR), spontaneous skin potential response (SRPK, or SSPR), skin resistance level (SRL, or SRL), skin resistance response (RSR). , or SRR), skin conductance level (UPrK, or SCL), etc. In this case, “level” means tonic activity (relatively long-term states), “reaction” - phasic activity (short, within a few seconds, responses to stimuli) and "Spontaneous" - reactions that are difficult to associate with any stimulus. The level of tonic electrocutaneous resistance is used as an indicator of the functional state of C. n. with. Relaxed, eg. during sleep, the resistance of the skin increases, and with a high level of activation it decreases. Phasic indicators react sharply to the state of tension, anxiety, increased mental activity.
Skin-galvanic phenomena have been studied in our country and abroad by various authors and in various directions. The physiological, reflex, physicochemical mechanisms of skin electrical reactions, the physicochemical nature of the electrical potentials of the skin and the influence of the nervous system on them, skin-galvanic reactions in healthy and sick people in the clinic were studied.
Registration and fixation of the galvanic skin response (or galvanic skin potential) for the purpose of instrumental lie detection is carried out using a polygraph and special software. The galvanic skin response (hereinafter referred to as GSR) is taken by means of a simple sensor consisting of two electrodes, which are attached to the human skin surface, in particular, to the “pads” of the nail (upper) phalanges of the fingers.
Despite the available studies (Vasilyeva V.K. - 1964; Raevskaya O.S. -1985), confirming the presence of some differences in skin potentials, depending on the place of removal of the GSR (left or right side of the body), in my opinion, this does not fundamental influence on the results of the interpretation of polygrams when conducting surveys using a polygraph. However, if you have a choice, I recommend shooting GSR from the fingers of the left hand, since it is traditionally believed that a more pronounced reaction is taken from the left hand, which is under the control of the “more emotional” right hemisphere of the brain.
In this paper, we use research materials obtained using the polygraph "KRIS" manufactured by Varlamov and the corresponding software "Sheriff".
It has been established that electrical phenomena in living tissues, including human skin, are due to ionic changes.
The study of GSR began in the 19th century. According to available data, in 1888 Feret and in 1889 Tarkhanov discovered two phenomena of skin electrical activity. Feret discovered that the resistance (electrical conductivity) of the skin changes when a current of 1-3 volts is passed through it in the dynamics of the impact of emotional and sensory stimuli. The phenomenon of GSR, discovered a little later by Tarkhanov, consists in the fact that when measuring the potential of the skin with a galvanometer, a change in this potential is detected depending on the emotional experiences of a person and the supplied sensory stimuli. Obviously, under such circumstances, the Feret method measures GSR by measuring skin resistance, and the Tarkhanov method measures GSR by measuring skin potential. Both methods measure GSR in the dynamics of the supply (presentation) of stimuli. In connection with the obvious dependence of GSR on mental phenomena, for some time GSR was called the psychogalvanic reaction or the Feret effect. The change in the potential of the skin was for some time called the Tarkhanov effect.
Later scientists (Tarkhanov I.R. - 1889; Butorin V.I., Luria A.R. -1923; Myasishchev V.N. -1929; Kravchenko E.A. - 1936; Poznanskaya N.B. - 1940; Gorev V.P. -1943; Kraeva N.P. - 1951; Vasilyeva V.K. -1960; Varlamov V.A. -1974; Kondor I.S., Leonov N.A. -1980; Krauklis A.A. -1982; Arakelov GG -1998 and many others) developed and confirmed the indicated ionic theory of bioelectric potentials. According to d.b.s. Vasilyeva V.K. (1964), one of the first in our country the ionic theory of bioelectric potentials and currents was substantiated by V.Yu. Chagovets (1903).
The simplest and clearest concept of GSR, from a psychological point of view, in my opinion, was proposed in 1985 by L.A. Karpenko: “Galvanic skin response (GSR) is an indicator of skin electrical conductivity. It has phasic and tonic forms. In the first case, GSR is one of the components of the orienting reflex that arises in response to a new stimulus and dies away with its repetition. The tonic form of GSR characterizes slow changes in skin conductance that develop, for example, with fatigue ”(A Brief Psychological Dictionary / Compiled by L.A. Karpenko; Under the general editorship of A.V. Petrovsky, M.G. Yaroshevsky. - M.Zh Politizdat, 1985, p. 144).
In 2003 Nemov R.S. gave the following definition: “Galvanic skin response (GSR) is an involuntary organic reaction recorded using appropriate devices on the surface of human skin. GSR is expressed in a decrease in the electrical resistance of the skin surface to the conduction of an electric current of low strength due to the activation of the sweat glands and subsequent moisturizing of the skin. In psychology, GSR is used to study and evaluate the emotional and other psychological states of a person at a given moment in time. By the nature of the GSR, they also judge the performance of various types of activities by a person ”(Psychology: Dictionary-Reference Book: in 2 hours - M .: VLADOS-PRESS Publishing House, 2003, part 1 p. 220).
The most concise definition of GSR can be found in N.A. Larchenko: “Galvanic skin response is an indicator of skin electrical conductivity that changes with various mental illnesses” (Dictionary-reference book of medical terms and basic medical concepts / N.A. Larchenko. - Rostov-na - Don: Phoenix, 2013, p. 228).
There are a lot of modern definitions of GSR, while there is no strict and precise generalizing theory of the galvanic skin response. Given the numerous scientific studies carried out in our country and abroad, we have to admit that many questions remain in the study of the GSR. “The electrical activity of the skin (EC) is associated with the activity of sweating, but its physiological basis has not been fully studied” (Psychophysiology: a textbook for universities / Edited by Yu.I. Aleksandrov, St. Petersburg: Peter, 2012, p. 40). Without going into a list of theories, it should be noted that for the purpose of instrumental lie detection, GSR is perhaps the most effective indicator of a person's psychophysiological activity. The most important for the instrumental detection of lies is the connection of the galvanic skin reaction with the physiological and mental processes of a person, the stable connection of the amplitude, length and dynamics of the GSR with verbal and non-verbal stimuli that cause it, as well as the fact that these connections are reflected to varying degrees. “Numerous studies conducted by various authors have shown that GSR reflects the general activation of a person, as well as his tension. With an increase in the level of activation or an increase in tension, the skin resistance decreases, while with relaxation and relaxation, the level of skin resistance increases. page 17).
According to Varlamov V.A. “Analysis of data on the mechanism of occurrence and regulation of a skin reaction, its informative signs showed that:
- tonic skin reaction is a reflection of deep processes of functional restructuring in the central nervous system;
- the magnitude of the response of the galvanic skin reflex is directly dependent on the novelty of the stimulus, the typological features of higher nervous activity, the level of motivation of the subject and his functional state;
- the dynamics of the indicators of phasic CR can be a criterion for the degree of emotional overstrain of the human functional system. If a further increase in emotional stress leads to a decrease in phasic CR, then this indicates the limit of the subject's functional capabilities;
- methods of registration, measurement of the dynamics of skin resistance, or the potential of the skin, in terms of information content, do not differ;
— informative features of the RC curve are common to any periodic curves.
When analyzing CR, it is necessary to take into account the characteristics of the mobility of the nervous system of people, taking into account regional and national characteristics. According to the CR curve, it is impossible to determine which nationality representative is being tested, but the fact that he, for example, is a representative of the southern peoples, temperamental, with a mobile nervous system, can be determined. (Varlamov V.A., Varlamov G.V., Computer lie detection, Moscow-2010, p.63).
Given the above, I consider it appropriate to determine the main characteristics of the GSR necessary for accounting and understanding for the purposes of psychophysiological research (surveys) using a polygraph and the so-called instrumental lie detection.
Galvanic skin response (GSR) is an indicator of the electrical conductivity and resistance of the skin, its own electrical potential of the skin. It has been established that these indicators change in a person depending on external and internal conditions. The most important, in my opinion, conditions include: the psychological state of a person, the physiological state of a person, the adaptive capabilities of a person, environmental conditions, the strength, frequency and intensity of the stimulus presented, etc.
Galvanic skin response (GSR) has phasic and tonic components. The phasic component characterizes the psychophysiological reaction associated with the recognition of the presented stimulus. These characteristics are associated with the recognition of such components of the presented stimulus as its novelty, intensity, suddenness-expectancy, strength, semantic content, and emotional significance. The tonic component characterizes the psychophysiological state of the organism under study, the degree of adaptation to the presented stimulus.
The galvanic skin response (GSR) under controlled conditions is practically not amenable to correct conscious control. In the presence of external or internal conditions affecting the state of the GSR, by the nature of the change in the phasic and tonic components of the GSR, one can quite objectively determine the qualitative characteristics of the influencing factors. This circumstance makes it possible to fairly objectively distinguish spontaneous GSR from arbitrary GSR.
The galvanic skin response (GSR) at the time of a psychophysiological study using a polygraph can be considered as an indicator of the degree of recognition of the presented stimulus, an indicator of emotion, an indicator of a stress reaction, an indicator of the functional state of the body, and all of the above at the same time.
It is known from classical psychophysiology that GSR is associated with the thalamic and cortical regions of the brain. It is believed that the activity of the neocortex is regulated by the reticular formation, while the hypothalamus maintains autonomic tone, the activity of the limbic system, and the overall level of human wakefulness. It has also been proven that GSR is partially influenced by the human parasympathetic system.
Fragment from the book "Encyclopedia of the polygraph"
galvanic skin response - GSR) - bioelectrical activity, fixed on the surface of the skin and due to the activity of the sweat glands, - an indicator of the electrical conductivity of the skin. It acts as a component of the reactions of the emotional body associated with the work of the sympathetic nervous system. It can be recorded from any area of the skin, but the fingers and hands or soles of the feet are usually used. It serves to analyze the states of a person, his emotional-volitional and intellectual processes. Has two forms:
1) the physical form is one of the components of the orienting reflex, arising in response to a new stimulus and fading with its repetition;
2) tonic form - characterizes slow changes in skin conductivity, which develop, for example, with fatigue.
In the structure of the galvanic skin reaction, various components can be distinguished:
1) the level of tonic activity - as a kind of background, relatively long-term state;
2) reaction in response to stimuli - which lasts for several seconds;
3) spontaneous reactions - not associated with a specific stimulus. At the same time, the level of tonic activity acts as an indicator of the functional state of the central nervous system: skin resistance increases in the state of relaxation, decreases with activation.
Change in the electrical resistance of the skin. GSR is widely used in measuring activation levels and is commonly associated with the idea of a lie detector.
Galvanic skin response (GSR)
Specificity. Bioelectrical activity, fixed on the surface of the skin, due to the activity of the sweat glands. It acts as a component of various functional states, an orienting reflex, emotional reactions of the body associated with the work of the sympathetic nervous system. Bears the imprint of individual differences. It serves to analyze the states of a person, his emotional-volitional and intellectual processes.
Kinds. In the structure of the GSR, various components can be distinguished:
The level of tonic activity as a kind of background, relatively long-term state,
A response to stimuli that lasts for several seconds
- "spontaneous" reaction, unrelated to any specific stimulus.
At the same time, the level of tonic activity acts as an indicator of the functional state of the central nervous system: skin resistance increases in a relaxed state, decreases when activated.
Diagnostics. It can be recorded from any area of the skin, but the fingers and hands or soles of the feet are usually used. For registration, measurement can be carried out:
Differences in skin potentials (Tarkhanov's method, developed in 1890);
Changes in skin resistance (Fere's method, developed in 1888).
GALVANIC SKIN RESPONSE
Measuring the electrical sensitivity of the skin with a galvanometer. Two methods are used: the Feret measurement, which records changes in skin resistance when a weak electric current is passed, and the Tarkhanov measurement, which records the weak current actually produced by the body. Since Feret's measurements increase with sweating, it has often been suggested that it is an indicator of emotional tension or anxiety. It turned out that this assumption is difficult to substantiate, and perhaps it is best to consider this indicator simply as a measure of physiological arousal: see lie detector, polygraph. There are alternative names for the skin reaction, which are usually used synonymously, for example, psychogalvanic reaction, electro-dermal reaction, electrical skin reaction, Feret's phenomenon and Tarkhanov's phenomenon.
GALVANIC SKIN RESPONSE (GSR)
an indicator of the electrical conductivity of the skin, estimated by the value of the electrical resistance of the skin or the difference in electrical potentials between two points of the skin. The most pronounced GSR occurs when it is registered from the fingertips, palms and back surface of the hands, as well as from the sole of the foot. GSR has phasic and tonic forms. In the first case, GSR is one of the components of the orienting reflex that arises in response to a new stimulus and dies away with its repetition. Unlike phasic short-term GSR, the tonic form characterizes slow changes in electrical skin resistance. Its value can serve as an indicator of the functional state of a person. In sleep, when vigilance is lost, the resistance value becomes greater, and when the level of body activation is high (for example, in a state of emotional stress), it decreases. Phasic fluctuations in electroskin potentials that spontaneously arise in the absence of external stimuli also reflect the human condition associated with anxiety, tension, and internal mental activity. In general and engineering psychology, GSR is widely used as a tool for monitoring and diagnosing the functional state of a person, as well as in studies of intellectual activity, features of the emotional and volitional spheres of a person. Based on the analysis of the GSR, such a device as a lie detector was built (see also Electric activity of the skin).
In 1888, Dr. Feret described the following case. A patient with hysterical anorexia, whom he tactfully refers to as "Madame X," complained of electrical tingling sensations in her hands and feet. Feret noticed that these sensations intensified when the patient inhaled some smell, looked at a piece of colored glass, or listened to the sound of a tuning fork. We do not know whether the patient's tingling in the extremities ceased, but during the examination Feret found that when a weak current was passed through the forearm, there were systematic changes in the electrical resistance of the skin. Two years later, Tarkhanov independently showed that similar electrical shifts can be observed without the application of an external current. Thus, he discovered the skin potential and, in addition, established that this potential changes both during internal experiences and in response to sensory stimulation.
Later, this electrical activity of the skin was called the "galvanic skin response" (CSR). This term has survived to this day. Although it was difficult to measure such subtle shifts with primitive instruments used at the beginning of the century, the predictability and drama of GSR has attracted the attention of many researchers. If you have never observed this simple phenomenon, it will be difficult for you to imagine the excitement of the early explorers who saw endless possibilities in this field. Imagine that your fingers are connected to a huge machine with the help of an intricate tangle of wires and that you are in an old laboratory of the beginning of our century. Now imagine that every time you mentally imagine the face of a friend, the arrow of the measuring device moves!
One of the first researchers of the GSR was Carl Jung. He viewed GSR as an objective physiological "window" into unconscious processes, which was postulated by his mentor Freud. It was in Jung's work that it was first shown that the magnitude of the electrical reaction of the skin reflects, apparently, the degree of emotional experience. The more you are affected by what you imagine, the more the arrow deviates.
In this atmosphere of enthusiasm, hundreds of scientists began to use their cumbersome equipment to determine in which situations GSR arises. In one study of fear, Nancy Bailey tested her fellow students with the following stimuli: they listened to a story about cattle drowning in the sea; they held a burning match in their hand until it began to burn their fingers; then, four feet away, a revolver was fired, loaded with a blank cartridge which made a particularly loud sound; and some were given this revolver to shoot themselves. Based on the subjective report of the subjects and the analysis of physiological reactions, Bailey came to the conclusion that there are two types of fear: fear of surprise and fear due to understanding of the situation. Waller studied GSR in subjects who mentally imagined a German air raid on London, and Linde (1928) found that funnier jokes consistently produced greater GSR (to the delight of psychophysicists, this relationship turned out to be a Weber-Fechner logarithmic curve).
The electrical changes in the skin are so striking and so easy to measure that where psychophysiologists were looking for the basic laws of behavior, other people saw practical possibilities. At one time, advertising agencies were looking at whether the GSR in response to an advertisement could predict how effectively the advertisement would influence the sale of a product. In one preliminary study, a group of housewives had the highest GSR for pancake flour ads that were actually more effective than other ads. However, the same experiment, carried out on the same group of subjects with advertisements for baby food, was less successful. No wonder. This and many other similar studies were based on the assumption that the advertising that causes the most emotional reaction in people should have the greatest effect on the sale of the product; but this assumption in different cases could be both true and false. Be that as it may, the use of GSR in advertising turned out to be another short-lived fad.
Many electronic equipment companies now sell inexpensive devices that can produce tones of varying pitch or loudness depending on the resistance in the circuit. A person can become the soul of the evening if, by connecting such a machine to the palms of an unsuspecting friend, he asks him purely personal questions. The machine will probably begin to publish treacherous screams in all cases when he lies. This is, of course, just a harmless toy, but only as long as it is not used to invade the privacy of innocent viewers.
More expensive versions of the same devices are sold in the name of science and religion. It can be said that the less sophisticated the consumer is in worldly affairs, the sooner he will pay money to measure the reaction of his sweat glands.
1. A method for recording galvanic skin reactions, including fixing two electrodes on the human body, applying an electric voltage to them, registering the change in time of the electric current flowing between the electrodes and fixing current pulses in the frequency band of the physical component of the electrodermal activity, characterized in that they analyze the shape of each pulse in the sequence of pulses in the frequency band of the physical component, for which the signal is recorded in the form of a time derivative of the logarithm of the numerical value of the electric current, the magnitude of the trend is determined due to changes in the signal in the frequency band of the tonic component of the electrodermal activity, and the value of the first derivative is corrected by subtracting from it the trend value, register the second time derivative of the logarithm of the numerical value of the electric current, determine the beginning of the pulse of the mentioned signal by the moment the second derivative of the threshold value is exceeded, and then determine They determine the correspondence of the pulse shape to the established criteria, and if there is such a correspondence, the analyzed pulse is referred to the pulses of the physical component, and in the absence of such a correspondence, they are referred to as artifacts.
2. The method according to claim 1, characterized in that the trend value is determined as the average value of the first derivative over a time interval, preferably from 30 to 120 s.
3. The method according to claim 1, characterized in that the trend value is determined as the average value of the first derivative over a time interval of 1 - 2 s, provided that the values of the first and second derivatives are less than the specified threshold values during this time interval.
4. The method according to any one of claims 1 to 3, characterized in that the arrival time of the pulse of the first derivative is considered the moment when the second derivative exceeds the threshold value by at least 0.2%.
5. The method according to any one of claims 1 to 4, characterized in that when determining the shape of the pulse, the values of the maximum f max and minimum f min of the values of the first derivative are recorded minus the trend value, their ratio r, the time interval t x between the minimum and maximum of the first derivative , while the moments of reaching the maximum and minimum values of the first derivative are determined by the moment of sign change of the second derivative.
6. The method according to claim 5, characterized in that the criteria for belonging of the analyzed pulse to the signal of the physical component of the electrodermal activity are inequalities
0,5 < f max < 10;
-2 < f min < -0,1;
1,8 < t x < 7;
1,5 < r < 10.
7. A device for recording galvanic skin reactions, containing electrodes with means for their fastening connected to the input device, means for suppressing impulse noise, means for isolating a signal in the frequency band of the physical component of electrodermal activity, means for detecting pulses of the physical component, a registration unit, characterized in that the means for separating the signal in the frequency band of the physical component, the means for suppressing impulse noise and the means for detecting pulses of the physical component are made in the form of a low-pass filter connected in series to the input device, a block for converting the input signal into the first and second time derivatives and a block pulse shape analysis, while the output of the latter is connected to the input of the registration unit.
8. The device according to claim 7, characterized in that the input device is a stabilized source of electrical voltage and a resistor connected in series to the electrodes, a logarithmic amplifier with a differential input stage, while the resistor shunts the inputs of the logarithmic amplifier.
9. The device according to claim 7 or 8, characterized in that the unit for converting the input signal into the first and second time derivatives is made in the form of the first and second differentiators and a low-pass filter, while the output of the first differentiator is connected to the inputs of the second differentiator and the low-pass filter frequencies whose outputs are block outputs.
10. The device according to any one of claims 7 to 9, characterized in that the shape analysis unit includes means for determining the maximum rate of change of the signal at the leading and trailing edges of the analyzed pulse, means for determining the asymmetry of its shape, means for determining the pulse width, means for comparing the mentioned values with the established limits for generating a signal that the analyzed pulse belongs to the signal of the physical component of the electrodermal activity.
11. The device according to claim 7, characterized in that the low-pass filter, the unit for converting the input signal into the first and second time derivatives and the unit for analyzing the shape of the pulses are made on the basis of a computer connected to the input device via an analog-to-digital converter.