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“Pavlov, Ivan”, The Encyclopedia of Learning and Memory. (L. Squire, Ed.), New York: Macmillan, 513-16.
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PAVLOV, IVAN
Ivan Petrovich Pavlov (1849--1936) is best known as
the discoverer of the conditioned reflex (see
Figure 1: Ivan Pavlov. Courtesy National Library of
Medicine
conditioning, classical and instrumental.) His
motto, "Observation and Observation!," like that of
Socrates ("The unexamined life is not worth living,"
or, more precisely, "The uninquiring life is not the
life for man"), encapsulates the life and work of this
Nobel laureate physiologist, whose influence on
psychology in general, and on learning and memory
in particular, has been enormous.
Pavlov's life may be viewed as a move from a
religious to a scientific perspective. His ancestry can
be traced to an illiterate eighteenth-century serf
known only by his first name, Pavel (Anokhin,
1949). Pavel's son gained emancipation and became
a member of the clerical estate; during the next two
generations, the family head rose through the
religious hierarchy from church sexton to deacon.
The deacon was able to provide a seminary
education for his sons, who became ordained priests.
The youngest of his three sons, Pavlov's father, Petr
Dmitrievich, became a priest in Riazan.
As Windholz's (1991) account indicates, Petr
Pavlov, who had a library of his own, transmitted to
his son a scholastic attitude toward knowledge. The
father's advice to his children was that any book
should be read at least twice, in order not
to miss anything important and to recall it more
accurately. His son Ivan took this advice to heart
throughout his scientific career but could not accept
his father's position on fundamental (including
religious) issues. According to a later account by
Ivan, "I had heated arguments with my father, which,
because of my position, led to strong words and
ended in serious disagreements" (Pavlov, 1952, p.
447). The exact nature of the disagreements is hard to
specify, but Windholz's suggestion is probably
correct—that significant components were Pavlov's
loss of faith by the time he entered the seminary in
Riazan and his decision to leave the seminary before
completing his studies. In 1870, he entered the
natural sciences section of the Faculty of Physics and
Mathematics at St. Petersburg University. His father
refused to support him financially, yet he had
probably unwittingly set the stage for it by providing
an intellectual oasis during Pavlov's seminary period.
Unlike most seminary students, "Pavlov lived in his
parents' home which gave him considerable freedom
to pursue his own intellectual interests" by being
"able to avoid the discipline imposed upon seminarians living in the dormitory and enjoy [ing]
uninhibited reading in a small room over the family
living quarters" (Windholz, 1991, p. 58).
For psychology, and for his later interests, perhaps
the most important book that the young seminarian
may have read in that small room was Ivan
Sechenov's Reflexes of the Brain (1866). Sechenov
had had a brush with the authorities (the government
censor), who forced him to change the more explicit
title An Attempt to Place Psychical Processes on a
Physiological Basis to the more neutral published one
(Koshotiants, 1945). Nevertheless, the idea that by
studying behavior it is possible to give an account of
subjective processes is evident in Sechenov's thought
and constitutes Pavlov's objective method in
psychology, that is, the objective study of mental
processes. It is important to stress that in this method,
the only restriction on "the levels of explanatory
constructs that are used [is] that the evidence
concerning those constructs be stated in an objective
or scientifically communicable way" (Furedy,
Heslegrave, and Scher, 1984, p. 182). Thus there are
no Watsonian (e.g., Watson, 1913) or Skinnerian
restrictions on the nature of theoretical concepts, but
only on the mode of evaluation of the inferences
about those concepts. (See WATSON, JOHN B.;
SKINNER, B. F.)
514
Pavlov, Ivan
Like Sechenov, Pavlov was a revolutionary
thinker who, however, was able to deal with authority without either surrendering on vital points or
being forced to oppose at the cost of personal ruin.
An early instance of this flexibility is that a seminary
inspector stated on a written certificate at the end of
Pavlov's period of study that "thoughts contrary to
the Christian religion ... I never noticed in him"
(cited in Windholz, 1991, p. 63), well after Pavlov's
religious arguments with his father. Much later, after
he had achieved the pinnacle of scientific status for
his work on the physiology of digestion (the Nobel
Prize, 1904), and had then turned to the study of the
"psychic" salivary (digestive) reflex (i.e., Pavlovian
conditioning), he was able to maintain an active
laboratory throughout the reign of Stalin, a
considerable testament to his political skills.
Yet Pavlov also showed great courage in challenging authority. Horsley Gantt, a young American
scientist who was a visiting member of Pavlov's
laboratory in the 1920s, recounts that in 1926 the
minister of education and head of the department
that supported Pavlov's laboratory came on a site
visit, but Pavlov refused even to meet with him,
much less show him his laboratory. His stated reason
was that he disapproved of the minister's recent
book, The ABC of Communism (Gantt, 1991, p. 68).
The fact that Pavlov's laboratory survived and
thrived following this piece of incredible political
insolence suggests both his intellectual integrity and
his skill in knowing just how far he could go in
challenging authority. He shared with Socrates and
other great thinkers the passion for inquiry and the
world of the mind, but unlike Socrates he retained
the practical skills necessary to survive in the
political world.
One mark of Pavlov's fame is that he is one of the
handful of modern thinkers whose name is used
adjectivally to describe concepts. Pavlovian concepts
in psychology are widely referred to and may be
classified in three areas, the last of which is the most
relevant to learning and memory. The first area is
that of popular psychology, wherein the term
Pavlovian
response
refers
to
automatic,
nonreflective, reflexlike reactions. In this vein, the
brainwashing activities of the Chinese and the North
Koreans in the 1950s were considered to be
"Pavlovian," and much of orthodox Marxist writings
in psychology during the same period in the Soviet
Union paid lip service to "Pavlovian principles."
Of general scientific interest for personality
theory
is the Pavlovian notion of differing strengths in the
nervous system, a concept that arose from Pavlov's
study of experimental neurosis occurring from the
breakdown of conditional discrimination in dogs. In
the West, Eysenck's work on extraversion and
introversion draws heavily on these Pavlovian
concepts. Detailed analysis of this psychological (and
physiological) theorizing is not relevant here, but it is
worth noting that the theoretical ideas and concepts
involved are quite complex and go well beyond the
observable data that Watson (1913) argued were the
only proper subject matter of psychology.
For the psychology of learning, however, Pavlov's
most important concept is indubitably that of the
conditioned reflex, which is a form of learning
resulting from "classical" or "Pavlovian" conditioning. In classical conditioning, a stimulus (e.g.,
food) that unconditionally elicits the to-be-learned
response (e.g., salivation, the unconditioned response
or UR) is paired with a "neutral" stimulus (e.g., bell)
that, conditional on being paired repeatedly with the
unconditioned stimulus (US), comes to elicit
salivation as the conditioned reflex or response (CR).
In Pavlov's view, the classical conditioning
preparation was contrary to "subjective psychology
[which] held that saliva flowed because the dog
wished to receive a choice bit of meat" (Grigorian,
1974, p. 433). This sort of cognitive and purposive
formulation is akin to interpretations of the Skinnerbox bar press, instrumental conditioning in terms of
bar-pressing being emitted by the rat "in order to get
the food."
The conditioned reflex concept was of considerable theoretical importance in psychology during the
heyday of LEARNING THEORY in the 1940s and 1950s.
During this period, learning theory was viewed as
primary, as illustrated by the dictum that learning
theory is behavior theory. And classical conditioning
was considered to be the basic building block that
underlay all forms of learning and behavior. The
dominant learning-theory approach was that of the
stimulus-response (S-R) theorists like C. L. HULL
(1943) and K. W. SPENCE (1956), and an important
concern was the theoretical attempt to account for
apparently cognitive, stimulus-stimulus behavior in
terms of S-R principles, that is, through the learning
of responses only. The fractional anticipatory goal
response construct was the S-R theoretical concept of
choice, and both Hull (1931) and Spence (1956)
specifically asserted that this theoretical response
mechanism
was
learned
through
classical
conditioning.
Pavlov, Ian
In addition to such theoretical usage of classical
conditioning, there was widespread empirical research directed at observing the acquisition and
extinction of the CR as a phenomenon in its own
right, although the dominant preparation under study
was not the animal salivary one but the human eyelid
conditioning experiment. In this preparation, an air
puff to the eye served as the US, a blink as the UR
and CR, and (usually) a tone as the CS (conditional
stimulus). Consistent with the prevailing S-R
emphasis, eyelid conditioning was found to be
critically determined by various independent variable
manipulations and dependent variable measurements.
Concerning independent variables, the most
important one was the period between CS and US
onsets, the CS-US interval. The optimal CS-US
interval was slightly less than 0.5 second, and CS-US
intervals of 2 seconds or greater produced no
conditioning at all (i.e., no increase in CS-elicited
blinks as a function of paired CS-US trials). The CSelicited response latency measurement was also
found to be crucial: shorter-latency blinks (occurring
within 150 milliseconds following CS onset) were
found to decrease rather than increase as a function
of repeated CS-US pairings, so that only longerlatency blinks (the frequency of occurrence of which
did increase as a function of CS-US pairings) were
classified as CRs.
The decline of the S-R approach in psychology
and the "paradigm shift" to the cognitive, S-S approach resulted in a radical shift in theoretical
perspective on Pavlovian conditioning. According to
its most famous modern exponent, Pavlovian
conditioning is "now described as the learning of
relations among events so as to allow the organism
to represent its environment" (Rescorla, 1988, p.
151). It is interesting to compare this cognitive
("relations between events") and purposive ("so as to
allow") formulation with the "subjective psychology" account cited above, which Pavlov opposed. At a more empirical level, the 1970s and
1980s also saw the virtual abandonment of the eyelid
preparation as a means of studying the Pavlovian
(response) conditioning phenomenon. An improved
form of the preparation (the rabbit nictitating
membrane preparation developed in the 1960s) has
been employed, but predominantly as a technique to
study the effects of physiological manipulations
rather than the phenomenon of conditioning itself.
Consideration of the CS-US interval has essentially
disappeared, to the extent that, in the currently
dominant Rescorla-Wagner (1972) model of
Pavlovian conditioning, the CS-US interval
515
does not appear as a parameter. Considering the fact
that, as indicated above, the CS-US interval is crucial
in preparations such as eyelid conditioning, this
omission may seem strange. However, most of the
evidence and experimental work of current cognitive
S-S Pavlovian conditioners is based on preparations
where conditioning is not measured directly through
assessing the CR, but indirectly through assessing the
effect of the CS on some instrumental indicator
behavior, as in the conditioned emotional response
preparation. Such indicator-behavior preparations are
more likely to suggest that Pavlovian conditioning is
the learning of "relations between events" (i.e.,
cognitive, S-S learning of CS/US contingency) rather
than the learning of (conditional) responding (i.e., the
CR) to the CS.
It is also interesting to note that not only during
the current cognitive S-S phase, but also during the
earlier S-R phase, of Western experimental psychology, no body of systematic reports of Pavlovian
dog salivary conditioning emerged in the journal
literature. Pavlov's methods were based on single case
studies, and the dependent variable differences were
reported quasi-anecdotally rather than with specified
reliability in terms of the rules of statistical inference.
Furthermore, his preparation is extremely difficult to
work with. For example, the typical subject requires
some 3 months of adaptation to the holding harness
before the food reliably elicits salivation rather than
competing struggling behavior. Still, the Pavlovian
emphasis on using behavior as the objectively
observed dependent variable has been retained by
both the S-R experimentalists and their cognitive, S-S
oriented successors.
The Pavlovian emphasis on observation has been
carried on as an intellectual tradition by the Pavlovian
Society. This international organization was founded
in the United States in 1955 by Horsley Gantt, who,
as noted above, worked in Pavlov's laboratory in the
1920s. The official journal of this society was first
Conditional Reflex, then Pavlovian Journal of
Biological Science, and, most recently (1991),
Integrative Behavioral and Physiological Science.
Although few members of this interdisciplinary group
(whose backgrounds and interests range from singlecell physiology to psychoanalysis) specialize in
classical-conditioning research, the common ground
is provided by the society's motto ("Observation and
Observation"). To them it means that whatever the
differences may be between favored theoretical
positions, the
516
Pavlov, Ivan
issues should be debated in the light of the observed
evidence.
REFERENCES
Anokhin, P. K. (1949). Ivan Petrovich Pavlov. Zhizn,
deiatel'nost i nauchnaia shkola Moscow and Leningrad:
Izdatel'stvo Akademii Nauk SSSR.
Furedy, J. J., Heslegrave, R. J., and Scher, H. (1984).
Psychophysiological and physiological aspects of Twave amplitude in the objective study of behavior.
Pavlovian Journal of Biological Science 19, 182-194.
Gantt, W. H. (1991). Ideas are the golden coins of science. Integrative Physiological and Behavioral Science
26, 68-73.
Grigorian, N. A. (1974). Pavlov, Ivan Petrovich. In Dictionary of scientific biography, vol. 10, pp. 431—435.
New York: Scribner.
Hull, C. L. (1931). Goal attraction and directing ideas
conceived as habit phenomena. Psychological Review
38, 487-505.
-------- (1943). Principles of behavior: An introduction
to behavior theory. New York: Appleton-CenturyCrofts.
Koshotiants, K. S. (1950). /. M. Sechenov. Moscow. Izdatel'stvo Akademii Nauk SSSR.
Pavlov, I. P. (1952). Ivan Petrovich Pavlov (avtobiografiia). In his Polnoe sobranie sochinenii, vol. 6.
Moscow and Leningrad: Akademii Nauk SSSR.
Rescorla, R. A. (1988). Pavlovian conditioning: It's not
what you think it is. American Psychologist 43, 151—
160.
Rescorla, R. A., and Wagner, A. R. (1972). A theory of
Pavlovian conditioning: Variations in the effectiveness
of reinforcement and nonreinforcement. In A. H. Black
and W. F. Prokasy, eds., Classical conditioning vol. 2,
Current theory and research New York: AppletonCentury-Crofts.
Sechenov, I. (1866). Refleksy golovnogo mozga St. Petersburg: Tipographiia A. Golovachova.
Spence, K. W. (1956). Behavior theory and conditioning.
New Haven: Yale University Press.
Watson, J. B. (1913). Psychology as the behaviorist views
it. Psychological Review 20, 158-177.
Windholz, G. (1991). I. P. Pavlov as a youth. Integrative
Physiological and Behavioral Science 26, 51—67.
John J. Furedy