Excerpts from Lectures on Conditioned Reflexes, Volume II: Conditioned Reflexes and Psychiatry

Ivan Petrovitch Pavlov


Pavlov’s laboratory, built for him by the Soviet government about 1930

Modern Definitions


Unconditioned Stimulus (US or UCS) Food A stimulus which produces an Unconditioned Response without conditioning being required
Unconditioned Response (UC or UCR) Salivation An automatic or inherent response to the Unconditioned Stimulus
Conditioned Stimulus (CS) Bell Initially neutral with respect to the Unconditioned Response which is, by conditioning, associated with the Unconditioned Stimulus
Conditioned Response (CR) Salivation The response to the Conditioned Stimulus once classical conditioning has been established
Classical Conditioning Salivation in response to a bell Said to have occurred when the Conditioned Stimulus produces the Conditioned Response

Pavlov’s Definitions


Ambivalence A symptom peculiar to schizophrenics appearing very intensively and extensively in the ultraparadoxical states (149)
Behaviourism At the present time, on the basis of nearly thirty years of experimentation done by myself with my numerous co-workers, I feel justified in asserting that the total external as well as internal activity of a higher animal, such as the dog, can be studied with complete success from a purely physiological angle, i.e., by the physiological method and in terms of the physiology of the nervous system (44)
Concentration The basic processes of the whole central nervous system are obviously identical – excitation and inhibition. There is sufficient reason to believe that the chief laws of these processes are irradiation and concentration and their reciprocal relations (87)
Conditioned Reflex The organism responds with a definite complex activity to an external excitation to which it did not respond previously (47). A temporary connexion between an external agent and the activity of the organism called forth in response to it (169)
Cyclism Succession of mania and depression (Gantt 14). Alternating periods of weakened activity and abnormally increased activity (184)
Delayed Reflex A special adaptation [due to inhibition], in order that the conditioned reflex might not occur prematurely, so that energy beyond the necessary measure is not uselessly expended (121)
Echolalia Syndrome common in schizophrenia: The pronunciation by the patient of the words of the one with whom he is conversing (41)
Echopraxia Syndrome common in schizophrenia: The performance of all the movements of the person to whom he is giving his attention (41)
Extinction A dog without cerebral hemispheres does not react to the mass of stimuli falling on him from the external world, the external world for him is, so to speak, contracted. Such a dog is not able to extinguish reflexes, for example, inhibition of the orienting reflex takes place only after many repetitions, while in the normal animal extinction occurs after 3-5 repetitions (66-7)
Feelings There is reason to think that the described physiological processes in the cerebral hemispheres correspond to what we subjectively call in ourselves, feelings, in the general form of both positive and negative, witht he innumerably shades and variations, thanks to either their various combinations or their different tensions. Here belong the feelings of difficulty and facility, alertness and fatigue, gratification and vexation, joy, triumph and despair, etc. Frequently, it seems to me that the depressed feelings experienced by a change in the customary mode of living, such as loss of a position or of loved ones, to say nothing of mental crises and shattered beliefs, have their physiological basis to a large extent in the changes, in the destruction of the old dynamic stereotypy with the difficulty of establishing a new one (100)
Freedom Reflex The reaction of struggling when the movements of the animals are hampered (53)
Hypersthenia In dogs of the excitory and strong type, the neurosis consisted in almost complete disappearance of the inhibitory reflexes, i.e., a marked weakening almost to zero of the inhibitory processes (cf. neurasthenia) (fn 74)
Hypnosis Paralysis of the motor skeletal musculature, especially of those muscles most concerned with the given excitation... animals stood like marble statues, drooling at the mouth but unable to take the food (Gantt, 14). Inhibition... has a tendency to spread, unless it meets with a counteraction in the conditions of a given environment. It expresses itself in phenomena of either partial or total sleep. Partial sleep is, evidently, the so-called hypnosis (51). Besides the conventional historical method of hypnotising dogs (turning them on the back and holding them in this unnatural position)... hypnosis can be produced by the continuation of one and the same stimulus, finally resulting in an inhibitory state of the corresponding cortical cells, representing on the one hand various degrees of tension and the other hand a varying extent of spread over the cerebral hemispheres and farther down into the brain (75)
Hypnotic Phase Intermediate phases between the waking state and complete sleep (39)
Hypnotism Naturally with the greater complexity of the human brain the hypnotic phenomena are considerably more varied in the human than in the animal. But it is possible that some of the hypnotic phenomena for one or another reason are more clearly marked in the animal, the more so because human hypnosis presents considerable variations depending upon the individual and the methods of hypnotization (40)
Hysteria Due to the weakness of the cerebral hemispheres in the hysteric there is a continual manifestation in different combinations of three special physiological phenomena: the readiness with which the hypnotic state occurs because even the habitual daily stimulations are ultramaximal and are accompanied by transmarginal overflow of inhibition (paradoxical phase), the extreme fixation and concentration of the nervous processes in separate points of the cortex, thanks to the predominance of the subcortex, and finally the extraordinary intensity and extension of the negative induction, i.e., inhibition in consequence of the reduced positive tonus of the other parts of the cortex (114)
Inhibition A protective mechanism. When the conditioned stimuli became too strong that the result produced would exceed the capacity of the given nervous system... excitation became replaced by inhibition, thus protecting the weak cortical cells from excessive excitation (Gantt, 14)
Inverse phase Phase associated with negativism (40)
Irradiation The processes of excitation and inhibition, originated at definite points of the cortex under the influence of corresponding stimuli, necessarily irradiate over a large or smaller area of the cortex, and then again concentrate in a limited space (the law of irradiation and concentration of nervous processes) (49)
Negativism In our experimental animals such negativism in our experimental animals was customary. With the conditioned food stimulus we feed the dog but he stubbornly turns away. Another interesting detail is especially marked in the inverse phase. When you remove the food from the dog he now attempts to get it. This can be repeated time after time. But when hypnosis disappears the dog greedily takes the food (40)
Neurasthenia In inhibitory and weak dogs [when neurosis was manifest], all positive conditioned reflexes vanished and the dog became very drowsy (cf. hypersthenia) (fn 74)
Neurosis This happens mainly under three conditions, three circumstances. Either extremely stong stimuli in the nature of conditioned stimuli are used in the place of those that are only weak or moderately strong and which ordinarily determine the animal’s activity; i.e., its excitory processes are overstrained. Or the animal is required to exert a very strong or a very protracted inhibition; i.e., its inhibitory processes are overstrained. Or, finally, a conflict between both these processes is produced; i.e., conditioned positive and negative stimuli are applied one right after the other. In all these cases witht he proper animal there develops a chronic disturbance of the higher nervous activity, a neurosis (84)
Orienting Reflex The investigatory reflex [to stimuli] (52)
Paradoxical Phase Phase in which the animal loses its reactions to strong stimuli, but reacts normally to the weak (40)
Periodicity Another fact which was frequently observed in the study of pathologic conditioned reflexes and which is obviously related to human neuroses and psychoses is the cyclism displayed by nervous activity. Disturbed nervous activity appeared to be more or less regularly fluctuating. First came a period of extremely weakened activity (conditioned reflexes were chaotic and often entirely disappeared or were reduced to a minimum); after several weeks or even months this was followed as though spontaneously and without any apparent reason by a more or less complete return to the normal condition – which was sometimes even entirely reestablished – only to be succeeded by another period of pathological activity. In other cases this cyclism was manifested by alternating periods of weakened activity and of abnormally increased activity. One cannot fail to see an analogy between these fluctuations and cyclothymia and manic-depressive psychoses (184)
Perseveration Many descriptive names may be applied [to this] pathological phenomenon – blockage, unusual inertia, increased concentration, exceptional tonicity. Henceforward we shall preferably use the term “pathological inertness” (153)
Reciprocal induction Having formed conditioned inhibition by differentiation we can see that such an inhibition is active rather than indifferent, because a positive stimulus used immediately after the inhibitory is without effect, showing the existence of an inhibitory state. This may be constant or, in the case of a delayed reflex, temporary, saving the cortex from useless work. The inhibition may spread (irradiation) or become concentrated, or evoke the opposite process – excitation (reciprocal induction) (63)
Schizophrenia The first to come under my observation was schizophrenia. My attention rested particularly on the symptoms of apathy, dullness, immobility and stereotyped movements, and, on the other hand, playfulness, unconventionality and in general childish behaviour inappropriate to patients with such illnesses (hebephrenia and catatonia)... I came to the conclusion that they are the expression of a chronic hypnotic state (39-40)
Sleep We have established beyond doubt the fact that sleep is inhibition spreading over all the hemispheres (39)
Stereotypy Stubbornly continued repetition of the same movements. In several of our dogs too this is clearly observed (40)
Supramaximal Supramaximal and transmarginal are both translated to ultramaximal (Gantt, 14)
Transmarginal Supramaximal and transmarginal are both translated to ultramaximal (Gantt, 14)
Ultramaximal Phase Stimulations which on account of their intensity produce an effect opposite to the normal stimulation (Gantt, fn. 88). Above a certain limit of intensity an excitory stimulus produces inhibition (103)
Unconditioned Reflex Making the cut [in the brain] still higher, extirpating only the cerebral hemispheres, you have very complex reflexes for the purpose of special movements to preserve the whole organism and its form. Such a dog arranges his internal activity well, and thanks to this he can remain healthy and live very much like a normal animal. He tries to get food, defends himself from every harm, does not tolerate a limitation of his movements; the orienting reflex is clearly present. These complex acts we call unconditioned reflexes (61). A permanent connexion between an external agent and the activity of the organism called forth in response to it (169)

Page numbers refer to Ivan Petrovitch Pavlov, Lectures on Conditioned Reflexes, Volume II: Conditioned Reflexes and Psychiatry, translated and edited by W. Horsley Gantt, Lawrence & Wishart Ltd., London 1941.

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