Pavlov’s classical conditioning

Chapter 3

What we are going to discuss

• Pavlov’s experiments and theories

– Some empirical relationships

• Reinforcement, extinction, spontaneous recovery.

• Generalization and differentiation.

– Pavlov’s other empirical relationships

• Favorable and unfavorable time relationships between conditioned and unconditioned stimuli.

– Conditioned and unconditioned stimuli do not overlap temporally.

» Simultaneous conditioned response.

» Delayed conditioned response

– Conditioned and unconditioned stimuli do not overlap temporally

» Short-trace conditioned response

» Long-trace conditioned response

» Backward conditioned response.

– Time interval functions as the conditioned stimulus

What we are going to discuss

• Varieties of inhibition

– External inhibition

– Internal inhibition

– Dis-inhibition

• Pavlov’s cerebral physiology

– Association, Irradiation, concentration and reciprocal induction

– Hypnosis and sleep

– Types of nervous system

– Second signal system

– Pathological states

• Estimate of Pavlov’s contribution to learning

Pavlov’s experiments and theories

• Some empirical relationships

• Reinforcement, extinction, spontaneous recovery.

– When reinforcement is discontinued and the conditioned stimulus is presented alone,

– the conditioned response gradually diminishes and disappears( experimental extinction) .

– after elapsed time without further repetition of any kind, the conditioned salivation has returned (spontaneous recovery)

Pavlov’s experiments and theories

• Generalization and differentiation.

– Generalization: is the tendency for the conditioned stimulus to evoke similar responses after the response has been conditioned.

• For example, if a child has been conditioned to fear a stuffed white rabbit, the child will exhibit fear of objects similar to the conditioned stimulus.

– Differentiation: is the ability to differentiate between a conditioned stimulus and other stimuli that have not been paired with an unconditioned stimulus.

• For example, if a bell tone were the conditioned stimulus, discrimination would involve being able to tell the difference between the bell tone and other similar sounds.

Pavlov’s other empirical relationships

• Favorable and unfavorable time relationships between conditioned and unconditioned stimuli.– Simultaneous conditioned response.

– The conditioned stimulus begins from a fraction of a second to 5 seconds before the unconditioned stimulus, and continues until the latter occurs.

– The conditioned response tends to follow the beginning of the conditioned stimulus almost immediately.

– Delayed conditioned response– The conditioned stimulus begins from 5 seconds to several minutes before the

unconditioned stimulus, and continues until the latter occurs. – Although the conditioned response begins before the unconditioned stimulus,

it follows the onset of the conditioned stimulus by a delay proportional to the length of the interval between the two stimuli.

– Delayed conditioned responses are difficult to form unless a simultaneous conditioned response has already been established.

Pavlov’s other empirical relationships

• Conditioned and unconditioned stimuli do not overlap temporally.– Short-trace conditioned response. The conditioned

stimulus is removed for a few seconds before the unconditioned stimulus begins.

– Long-trace conditioned response. The interval between the cessation of the conditioned stimulus and the beginning of the unconditioned stimulus is 1 minute or more.

– Backward conditioned response. The conditioned stimulus does not begin to act until after the cessation of the unconditioned stimulus.

Pavlov’s other empirical relationships

• Time interval functions as the conditioned stimulus.

– Temporal conditioned response: An unconditioned stimulus is presented at regular intervals of time. If it is now omitted, a conditioned response will occur at approximately the usual interval. Intervals as long as 3O minutes have been used successfully with dogs.

Discuss Varieties of inhibition

• The inhibitory phenomena within conditioning, first described in connection with extinction, became of great interest to Pavlov, and a classification of various types of empirical manifestations of inhibition was arrived.

• The summary by Hilgard and Marquis of these types of inhibition follows:

– External inhibition. Internal inhibition.

Discuss Varieties of inhibition

• External inhibition: Temporary decrement of a conditioned response due to an extraneous stimulus

– when a loud sound reduces conditioned salivation to a light.

Discuss Varieties of inhibition

• Internal inhibition: Internal inhibition develops slowly and progressively, when a conditioned stimulus is repeatedly presented under one of the following conditions.

– Experimental extinction.

– Differential inhibition

– Conditioned inhibition

– Inhibition of delay

• Experimental extinction. The weakening of response to a conditioned stimulus which is repeated a number of times without reinforcement.

• Differential inhibition. A conditioned response given originally to either of two stimuli is restricted to one of them through the reinforcement of one and the non-reinforcement of the other. The non-reinforced negative stimulus becomes inhibitory.

• Conditioned inhibition. A combination of stimuli is done ineffective through no reinforcement without only one stimulus which alone continues to evoke the conditioned response. The other stimuli in the combination are conditioned inhibitors.

• Inhibition of delay. If a regular interval of sufficient duration elapses between the start of a conditioned stimulus and its reinforcement, during the early portion of its isolated action the conditioned stimulus becomes not only ineffective, but actively inhibitory of other intercurrent activities. There may be temporary disinhibition at the onset of the conditioned stimulus, so that there is a slight conditioned response before the inhibition is manifested.

• Dis-inhibition

– Temporary reappearance of an inhibited conditioned response due to an extraneous stimulus.

– This may be considered as an external inhibition of an internal inhibition.

Pavlov’s cerebral physiology

• Association, Irradiation, concentration and reciprocal induction

– Association• the conditioned stimulus excites a center.

• The unconditioned stimulus excites another center

• These two build up a connection through attraction or drainage of impulses from first aroused center to the second.

• The direction of attraction is both a matter of time order

• relatively, the unconditioned center normally being more highly excited.

• Pavlov is clear that what he calls conditioning is what psychologists have called association.

• Thus, the temporary nervous connection is the most universal physiological phenomenon, both in the animal world and in ourselves.

• At the same time it is a psychological phenomenon—that which the psychologists call association

Pavlov’s cerebral physiology

• Association, Irradiation, concentration and reciprocal induction• Irradiation

– that provides the basis for generalization– Through the influence of corresponding stimuli.

– concentration• It provides the basis for differentiation. ( the capacity to

discriminate more and more precisely)• finer analysis would be destroyed if irradiation were not

corrected by concentration of excitation back to the original special cells.

Pavlov’s cerebral physiology

reciprocal induction• The interrelations of Irradiation and concentration are governed

by reciprocal induction• Thus differentiation by the methods of contrasts, in which the

positive stimulus is reinforced, the negative one not, develops an inhibitory process in relation to the negative stimulus that reduces the irradiation of excitation from the positive stimulus, and concentrates it where it belongs.

• The inhibition irradiates also, which can be demonstrated by showing that immediately after presenting the negative stimulus the response to the positive one is also weakened.

• This is true in the early stages of the establishment of a differentiation; later, when both excitation and inhibition have been concentrated, reciprocal induction takes place.

Pavlov’s cerebral physiology

• Hypnosis and sleep• The irradiation of weak inhibitory processes over the cortex produces a state

of partial sleep that is called by Pavlov hypnosis and related by him to hypnotic phenomena familiar in man.

– There are some peculiarities in the behavior of conditioned responses when a dog is in this state of irradiated weak inhibition. Three phases are associated with the condition:

» Equalization phase: all conditioned stimuli are equal in effect, regardless of intensity.

» Paradoxical phase: weak stimuli yield more secretion than strong ones.

» Ultraparadoxical phase: positive conditioned stimuli are ineffective; negative stimuli now produce secretion.

• If the irradiation of inhibition is more widespread, and the inhibition more intense, then sleep ensues.

• It was found that if vision, hearing, and olfaction were all destroyed at once through damaging the sense organs without injuring the central nervous system, the dog would sleep as much as 23 hours per day

Pavlov’s cerebral physiology

• Types of nervous system• Pavlov recognized four types of genotypic nervous system.

• These four types has similarity with ancient classification of temperaments that has come down from Hippocrates.

• sanguine (optimistic leader-like), choleric (bad-tempered or irritable), melancholic (analytical and quiet), and phlegmatic (relaxed and peaceful)

• Where excitation and inhibition are both strong, but equilibrated, two types arise. – If the states are labile, the sanguine temperament results;

– if they are inert, then the phlegmatic temperament is found.

• Where excitation and inhibition are both strong, but equilibrated un equilibrated, then the temperament is choleric.

• Finally, when both excitation and inhibition are weak, whether the states are labile or inert, – a melancholic temperament ensues.

Pavlov’s cerebral physiology

• Second signal system

• While in his own work Pavlov recognized that the ability to speak greatly enlarged man's potentialities

• later Soviet scientists have recognized that– The conditioned reflex mechanisms that man shares with lower animals

are grouped together as the first signal system.

– speech in man provides a second signal system.

• Pavlov speculates that the frontal lobes play an essential part in the operation of the second signal system

Pavlov’s cerebral physiology

• Pathological states

– He felt that the experimental neuroses animals were similar to neurasthenia in man.

– that persecution delusions corresponded to the ultra paradoxical phase in hynotic states in the dog.

– that catatonic schizophrenia was a hypnotic like state of protective inhibition.

– that manic-depressive reactions represented a derangement of the normal relations between excitatory and inhibitory processes.

– Obsessional neuroses and paranoia must be due to a pathological inertness of the excitatory processes of different motor cells.

PAVLOV'S CONTRIBUTION

• Capacity.

– The capacity to form conditioned reflexes is in part a matter of the type of nervous system.

– hence there are some congenital differences in learning ability..

PAVLOV'S CONTRIBUTION

• Practice:

– In general, conditioned reflexes are strengthened with repetition under reinforcement, but care always has to be taken to avoid the accumulation of inhibition, for inhibition may appear even within repeated reinforcement.

PAVLOV'S CONTRIBUTION

• Motivation

– There is no need to reduce motivation in classical conditioning because it is proved to be important for learning but Pavlov didn’t avouch the importance of motivation

PAVLOV'S CONTRIBUTION

• Understanding. – Such kind of Subjective terms are to be avoided.

– Pavlov finds no use for terms such as understanding or insight.

– but in one place he said that insight/ understanding means utilization of knowledge, utilization of the acquired connections.

– This is the characteristic associationist view of understanding: the utilization of past experience through some kind of transfer.

– The problem of novelty is not raised.

PAVLOV'S CONTRIBUTION

• Transfer:

– result of generalization

– By this process one stimulus serves to evoke the conditioned reflex in the case of another similar stimulus.

– In language system words substitute readily one for another, and thus permit wide generalization

PAVLOV'S CONTRIBUTION

• Forgetting. – Pavlov did not deal systematically with the retention or

forgetting of conditioned reflexes over time.

– partly because the same animals were used over and over again, their conditioned reflexes were greatly over-learned, and forgetting was not a laboratory problem.

– he always spoke of conditioned reflexes as temporary.

– It is important to distinguish between extinction and forgetting• Extinction involves unlearning something

• spontaneous recovery following extinction, and a weakened conditioned reflex is not therefore a forgotten one.

The End

Thanks