Thursday, April 30, 2020

Outline of Pavlov's lectures on Conditioned Reflexes 1927

What follows is my outline for Pavlov's Lectures Conditioned Reflexes (1927). Bracketed numbers refer to page numbers according Anrep's translation as found in the Classics in the History of Psychology page. The rest are my sparce notes. 

Lecture I


Recent physiological investigations

Investigative options

Through (then actual) psychology

Brand-new path of physiology stemming by the reflex as described by Descartes

A necessary reaction to an external stimulus through a definite nervous path

Objective and experimental


Pavlov's own frustrations in subjective methods

25 years of investigations and systematization (at the time of the lectures) with collaborators

Description of reflexes in general

These are for the survival of the organism (through adaptability)

Inhibitory and excitatory


Chains of reflexes

Identification of reflexes [12]

Example of freedom reflex

Investigatory reflex

Dynamic balance of reflexes in the organism



Lecture II



Choice of secretory reflex


Isolation from other stimuli [20]

Defense of isolation


Demonstration #1 [22]

Plain vanilla with metronome


Demonstration #2 [22]

Conditioned reflex. Signalization through sight . Food, conditioned itself


Demonstration #3 [23]

Food as an unconditional stimulus


Nomenclature of unconditioned and conditioned reflexes

Conditioning as learning


Conditions for successful conditioning [26, 392]

  1. It must overlap in time with the unconditioned stimulus;

The conditioned stimulus has to have some lead time;

The reverse doesn't generate a bond

  1. The organism has to be alert;

And free from any other nervous activity (as that arising from competing stimuli)

  1. A good state of health;
  2. The stimulus has to be mild or not overbearing.


Transformation of an unconditioned reflex into a conditioned one


Threshold of stimulus intensity


Lecture III


Second order conditioning

Third order conditioning found to be impossible


Conditioning through rituals [35]

Demonstration #4 [36]

Speculation on nervous connections


Characteristics of stimuli

Individual fluctuations in internal or external environment of the organism may, singly or collectively, acquire the properties of a conditioned stimulus



Trace conditioned reflex

Time lapse


Inhibition [43]




Description of external stimuli disrupting the conditioning of the dog [44]

Lasting effects

Old, established reflexes are more difficult to inhibit

Strength or unusualness of the stimulus has a proportional effect [46] !?

However, if not reinforced, they eventually lose their inhibitory powers !? Hence, they may be termed temporary inhibitory stimuli

Permanent external inhibition


Lecture IV


Internal inhibition

Develops progressively, often with difficulty, as opposed to external inhibition


Extinction (primary)

Weakening of the conditioned reflex by repeated application of the conditioned stimulus without reinforcement

Demonstration #5a

Fluctuations in the curve of extinction

External influences


Rate of extinction [51]

Peculiarities of each organism

Strength of previous conditioning

Number of trials

Intensity of the unconditioned reflex

Length of pause between successive repetitions

Secondary extinction

When primary extinction is happeningother conditioned reflexes are also affected notwithstanding if these are:

Homogeneous conditioned reflexes

Based on the same unconditioned reflex

Heterogeneous conditioned reflexes

On a different unconditioned reflex

After several extinctions even the unconditioned reflex might weaken [54]

The permanency of the secondary reflex also depends on

Its own reinforcement and extinction

If it's weaker than the primary reflex acted upon

When the stimulus is compound, the individual stimuli also suffer from secondary extinction

Similarly, the stronger the stimulus, the more effect it will have on the weaker and viceversa


Extinction beyond zero [58]

Measured by its effects on the secondary reflex

Spontaneous recovery

Demonstration #5b

Recovery by a few pairings

Extinction is regarded (by Pavlov) as a special case of inhibition and thus it cannot be completely destroyed. (Hence, nervous connections are rendered latent and subject to reestablishment)


Deviations in the curve of extinction


Temporary restoration of the condition reflects is regarded as a dis-inhibition [66] or inhibition of a inhibition


Lecture V


Internal inhibition (continued)

Combinations of stimuli

Conditioned inhibition/differential inhibition

An unreinforced combination will render an otherwise positive stimulus inactive

Temporal considerations

Overlap of a few seconds in the stimuli is of the essence for inhibition

A clear temporal separation of the stimuli renders the additional one as positive (of the second order) rather than inhibitory (provided it is not very intense, in which case it would work as an external inhibition)

Curve behavior [72]

Other factors

Character of the individual

Intensity of the stimulus

First establishment of an inhibitory process or a succeeding one


Summation or repetition of an inhibitory process [79]

Shortening of its effects

Dis-inhibition [82]

By the introduction of just another external stimuli the inhibition is partially lifted


Lecture VI


Internal inhibition (continued)


Interval between stimulus and reinforcement of the unconditioned reflex




By retarding a simultaneous reflex gradually

By jumping from a simultaneous reflects to a delayed one

There's an initial disappearance of the reflex, however, it gradually strengthens with enough trials and moves into intermediate position between the stimulus and the reinforcement

It is difficult to establish a delayed reflex without a previous application of a simultaneous regime

Intervening factors

Character of the individual

Type of conditioned stimulus used [90]

Trials during the preliminary stage

Whether the stimulus is continued or intermittent

Nature of the delay inhibition

Initially strong and not a gradual summation of the excitatory processes nor fatigue

Other stimuli acting on the delay phase

These may disrupt or not the inhibition depending on their type (strength)[94] or their repetition [98]

Initial excitatory behavior versus posterior inhibitory in the delay phase from one stimulus [103]

A compound stimulus is formed with the lapse of time experienced

Latent period

Brief recapitulation [106]

Experimental extinction

Conditioned inhibition

Inhibition of delay


Second order inhibition


Lecture VII


Reflex mechanisms

Analyzing mechanism

By which it selects out of the whole complexity of the environment those units which are of significance

Synthesizing mechanism

By which individual units can be integrated into an excitatory complex


Previous investigations of the analyzing mechanism

The superiority of the scope of the conditioned reflex



Initially, all the characteristics of the environment serve as a generalized stimulus and after some trials, the relevant stimulus from it come to the foreground, while those that are not, fall back [115]

Not based on dis-inhibition

Establishment of differentiations

Through repeated reinforcement

Not as effective if at all

By contrast [118, 122]

First, establish a reflex;

Present a similar, though contrasting in some aspect, stimuli without reinforcement;

Work from there to even finer contrasts


The non-reinforced stimuli lose their excitatory processes through inhibition […, 125]

Though not without fluctuations [120]

Can work with either positive or negative conditioned stimuli

Differential inhibition is the fourth type of internal inhibition


Intensity of the stimulus

Intensity of the unconditioned reflex



Lecture VIII


Instrumentation recap


Sense (analyzers) sensibility


Auditory [134]

Tone, pitch, rhythm

Instrument limits

Tactile [137]



Nutritive substances

Rejectable substances

Synthesis [141]

Compound stimuli

Overshadowing of different stimuli in type

Cutaneous is stronger than auditory; stronger than auditory; stronger than visual

Nevertheless, the weaker stimulus is necessary for the production of the conditioned reflects a when it has been compounded with a stronger one. Also on the weaker element can bring down a compound stimulus if it is not singly reinforced (inhibition).

If single stimuli already have served on conditioning, there is no overshadowing when compounded [IX]

Successive stimuli [145]

With same or different analyzers

Modifications of patterns

A set pattern can be differentiated from unreinforced ones although this, takes time

Individual stimuli lose their excitatory properties

Elementary and higher forms of analysis and synthesis [148]

Sense limits



Lecture IX


Irradiation and concentration

Internal inhibition initiated in a single definite point of an analyzer, rapidly irradiates over the whole analyzer, after which it is slowly concentrated upon its initial point. This can be traced.


Supposition that there is a correspondence between the analyzers and that of the cortex in regards of neighboring areas [154, 214]


Investigation of the nature of the phenomena [156]

Places of secondary and primary extinction


Auditory specific


Lecture X


Secondary inhibition of the other analyzers

Inhibition initiated in one analyzer reveals itself in other analyzers as well in the form of inhibitory aftereffect

Dependent on inhibition strength

Nonetheless the effect is weaker than in the primary analyzer


Experimental methodology [171]

Difficulties [175]


Aftereffects of the excitatory processes


Generalization of any recently established conditioned stimulus [185]


Lecture XI


Mutual induction


Positive induction

Inhibition leading to increased excitation

Following the extinction in some other area of stimulus within the analyzer

Not the form of dis-inhibition [190]

Depends on

The intensity of inhibition

Coarseness (or just how fine) of differentiation [194]

Coarser differentiation loses its induction when followed by finer training

Represents a temporary, phasic phenomenon in the establishment of inhibition

There are exceptions

Negative induction [196]

Excitation leading to increased inhibition

Difficulties in its investigation

Lecture XII


Interaction of irradiation and concentration with induction

These processes interact with one another

Sensitivity [208]

Of single non-reinforcement


Small influences over extended periods

Undulation (waves) in time and distribution of inhibition

Correspondence [214]


Positive induction applied to a definite place limits the spread of the inhibitory process


The interaction between expectation and mediation is determined either by the face of establishing new relations in the cortex or by the type of nervous system in different animals


Lecture XIII


The cortex as a mosaic of functions

Some cells respond to excitation while others to inhibition in a localized manner

Suggested problems (unresolved)

Functional demarcation

Its mechanism


Variability and stability [227]

Dynamic system [232]


Lecture XIV


Second kind of inhibition: inhibition in the cortex

Under the influence of conditioned stimuli that cortex sooner or later (sometimes very slowly) develops inhibition. This happens in a progressive manner

Frequent repetitions accelerates this process [237, 242]

This is attributed to the sensibility of the cortical elements which become functionally exhausted [244]

In other words, it is a protective mechanism



Shortening of the reinforcement delay

Avoiding many repetitions in one session

Interruption of the trials


Increase in the strength of the conditioned stimulus

Increase of the number of the conditioned stimuli (positive induction)

Increasing the strength of the unconditioned stimulus


When the inhibition has taken hold even the conditioned stimulus fails

A new conditioned stimulus restores the subject [239-241]


Lecture XV


A general spreading of this inhibition is possible: sleep or internal inhibition


Development of inhibitions

Prolonged action of a conditioned stimulus

Perhaps even more so with extinction

In differentiation it is clearer

Happens also with delayed reflexes


Starts with drowsiness and develops into deep sleep

The unconditioned stimulus even loses efficacy

With non-reinforcement

Reinforcement delays the progression of the secondary inhibition


Powerful stimuli (such as electric shocks) can also be found to develop internal and secondary inhibition


Some analyzers (senses) lend themselves more readily to inhibitions than others


Internal inhibition is explained as a scattered sleep [253] and functional fatigue [259]


Avoidance tactics [254]

The addition of other stimuli [255]

Even add to the sleep [258]

Monotonous stimuli on humans


Surgical investigations [259]


From sleep to inhibition [260]

With delays

Summation of inhibitions (cf. 256)


Excitation preceding drowsiness [263]


Final considerations


Lecture XVI


Transitional stages into sleep

Partial; localized sleep

Alert posture but unresponsive

Complete inhibition in the cortex; motor centers still free from inhibition



Subject's previous conditioning history

Numerous applications

Nature of the neutral stimuli

Weak and/or prolonged

Strong and short

May cause the spread of partial division into other areas of the cortex: "animal hypnotism" [269,312]


Variation of intensity in compound stimuli as a means of comparing them [269]

What can happen over many days (pathological) can be replicated in a few minutes in the transition to sleep

Paradoxical phase [271]

Strong stimuli do not have an effect while weak ones have a disproportionate one

Equalization phase

All the stimuli become equal in their effect

Intermediate (unnamed) phase

Medium strength stimuli have the greater effect

Return to normal


Relation to induction [276]


Narcotics [278]

Other transition controls [280]


No definite order in the phases can be established


Lecture XVII


Pathological disturbances arising from function


Dependence on types

Equal influences do not have the same effects […, 299]




Vivacious, but most likely to fall into drowsiness in the absence of stimuli. Predisposition to excitation […, 293]


Fraidy, but more apt to yield regular results under conditioning.  Predisposition to inhibition (Cf. Introverts).

Intermediate types [288]





Conflict between excitation and inhibition [292]



There is a breakdown of conditioned reflexes [290, ]. Acute neurosis





Rest [290,]

Stepping back and starting afresh [291, 319]

Chemical compounds [299]

Companionship [296]

Other stimuli [318]


Lecture XVIII


Transition from inhibition to excitation

Possibilities [311]

From a single point to the whole cortex

As injurious agent upon the cortex


Congenital weaknesses [312]

Definite conditions bring forth abnormalities

Types of stimuli according to intensity

The case of Petrograd 1924

Unusually strong stimulus

Breakdown of conditioned reflexes

Their restoration. Neurotic sequels (PTSD?)


Constitutions predisposed to inhibition become even more susceptible to it. Chronic pathological state [, 397]


Lecture XIX


Physical disturbances or interventions

Methodology and difficulties

Experimenter reflexes are the most likely to disappear well inherent, natural, reflexes are the first to resurface

Usually the greater the lesion, the greater it takes to recover

Recovered reflexes are often stronger [324] while inhibitions weaker

Complications [325]

Peculiar symptoms

Extirpation the whole cortex [328]

Simple reflex machine. Unconditionable

Acoustic analyzer centers [330]


Lecture XX


Visual analyser

Tactile analyser

Motor analyser


Lecture XXI


Activity after lesions

Example of reestablishment of conditioned reflexes [374]


Lecture XXII


Investigatory viewpoints

The one taken: the laws governing a complex system founded on the processes of excitation and inhibition

Determination and tabulation of different phases of the cortical activity

Absence or presence of inhibition or excitation

Their conditions

Their interrelations


Difficulties encountered [378]

Exquisiteness and complexity of the system



Reassessment of the old points of view

Secondary conditions [383]

Stimuli intensity


Way forward

Reducing the mass of various separate observations to terms of a progressive diminishing number of general more fundamental units [387]



Mechanism of dis-inhibition [390]

Necessary elements of conditioning



Lecture XXIII


Results in application to man



Habits identified as a chain of conditioned reflexes

Graduality in acquisition

Interruptions as disruptions of performance

Other similarities

Monotonous stimuli inducing drowsiness

Alertness and sleep

Pathological cases

Nervous and psychic disturbances

Violent changes in life, powerful stimuli…

(Petrograd 1924)

Cortex injury

Some individuals remain unaffected [397]

Identification with neurasthenia and hysteria [398]

Sleep disorders

Therapeutic measures [401]

Borderline states [404]

Hypnotic states


The conscious and the unconscious [410]


Final words

Much to explore and to systematize there still is


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