PAVLOV, IVAN (1849-1936)

The Russian physiologist Ivan Petrovich Pavlov is best known as the discoverer of the conditioned reflex. The life and work of this Nobel laureate is encapsulated in his motto, "Observation and observation!" His work had an enormous influence on psychology in general and on the theory of learning and memory in particular.

Early Life and Work

Pavlov evolved from a religious to a scientific framework. His ancestry tracex 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. Pavlov's father, Petr Dmitrievich, the youngest of these sons, was a priest in Riazan, an ancient town about 120 miles south of Moscow.

Petr Pavlov, as Windholz notes (1991), had a library of his own and transmitted to his son a love of knowledge. His 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; Ivan took this advice to heart throughout his scientific career. But he could not accept his father's position on some fundamental issues, including religious ones. "I had heated arguments with my father," Ivan wrote later, "which, because of my position, led to strong words and ended in serious disagreements" (Pavlov, 1952, p. 447). Windholz suggests that the main sources of discord were Pavlov's loss of faith by the time he entered the seminary in Riazan in 1864; he left before completing his studies there.

When, in 1870, Pavlov enrolled in natural sciences in the Faculty of Physics and Mathematics at St. Petersburg University, his father refused to support him financially. Yet his family unwittingly supported this important change by providing an intellectual oasis during Pavlov's seminary period. Windholz notes that, 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).

An 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 government censor, who forced him to change his original title—An Attempt to Place Psychical Processes on a Physiological Basis—to a less provocative one (Koshotiants, 1945). The idea that the study of behavior can yield an objective account of subjective processes is nevertheless evident in Sechenov's work. This assumption was the basis Pavlov's method in psychology: the objective study of mental processes. 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 or Skinnerian restrictions on the nature of theoretical concepts; the only restrictions pertain to the mode of evaluation of the inferences about those concepts.

Like Sechenov, Pavlov was a revolutionary thinker who was able to finesse his encounters with authority without surrendering on vital points or courting personal ruin. The ultimate testament of his political skill was his ability to run an active laboratory during Stalin's regime. By this time, he had achieved the pinnacle of scientific status for his work on the physiology of digestion (the Nobel Prize, 1904), and had turned to the study of the "psychic" salivary (digestive) reflex (i.e., Pavlovian conditioning). Yet Pavlov also showed courage in challenging authority and asserting his intellectual integrity. Horsley Gantt, a young American scientist who was a visiting member of Pavlov's laboratory in the 1920s, recounts that when, in 1926, the minister of education and head of the department that supported Pavlov's laboratory visited the site, Pavlov refused even to meet with him, much less show him the laboratory. His stated reason was that he disapproved of the minister's recent book, The ABC of Communism (Gantt, 1991, p. 68). The survival and subsequent success of Pavlov's laboratory in the wake of this political insolence suggests that he knew just how far he could go in challenging authority.

One mark of Pavlov's fame is that his name is attached to key psychological ideas. The term "Pavlovian response" usually refers to automatic, nonreflective, reflexlike reactions. (The "brainwashing" activities of the Chinese and the North Koreans in the 1950s were considered to be "Pavlovian." Orthodox Marxist writings in psychology during the same period in the Soviet Union paid lip service to "Pavlovian principles").

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, is of general interest for personality theory. In the West, Hans Eysenck's work on extroversion and introversion drew heavily on these Pavlovian concepts. The theoretical ideas and concepts are complex and go well beyond the observable data that Watson (1913) argued were the only proper subject matter of psychology.

Classical Conditioning

Pavlov's most important conceptual contribution, however, was in experimental psychology. His most influential concept is that of the conditional reflex, which Pavlov examined in an experimental preparation now known as "classical" or "Pavlovian" conditioning. In studying this form of learning, he presented canine subjects with food (the unconditional stimulus or US) that unconditionally elicited salivation (the unconditional response or UR) and with a bell (the conditional stimulus or CS) that originally did not elicit salivation. The CS, conditional on being paired repeatedly with the US, came to elicit salivation—a response termed the conditional 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 Skinner-box bar press, in which the rat is said to press a bar "in order to get the food."

While the classical conditioning preparation had been widely known in experimental psychology since the early twenties, no body of systematic reports of Pavlovian dog-salivary conditioning was published in the journal literature of experimental psychology. 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 canine subject requires some three months of adaptation to the holding harness before the food reliably (i.e., unconditionally) elicits salivation rather than competing struggling behavior.

The first set of systematic and extensive experimental explorations of the phenomenon of classical conditioning employed the human eyelid conditioning preparation. In this arrangement, an air puff to the eye (or, in later versions, an infra-orbital shock) served as the US, a blink as the UR and CR, and (usually) a tone as the CS (conditional stimulus). In the 1950s and 1960s many of the most rigorous of these studies were reported in Journal of Experimental Psychology, the leading experimental psychological journal of the period.

Most of the authors of these eyelid conditioning reports subscribed to the then dominant stimulus-response (S-R) approach to learning espoused by theorists like C. L. Hull (Hull, 1943) and K. W. Spence (Spence, 1956). According to the S-R approach, only stimulus-response associations were learned. This position contrasted with the position of the cognitive, stimulus-stimulus (S-S) theorists, led by R. C. Tolman, who argued that learning also involved both the acquisition of sign-signicate relationships such as "cognitive maps" as well as the teleological explanatory concept of purpose (e.g., Tolman, 1932).

Applied to the phenomenon of classical conditioning—widely considered to be the simplest form of learning—the S-R approach implies that conditioning is the learning of the association between a stimulus (the CS) and a specific response (the CR). Accordingly, most of these eyelid-conditioning experimenters (who produced a considerable volume of experimental evidence on the Pavlovian conditioning phenomenon) were sensitive to independent variables like the temporal contiguity between CS and US and to the dependent-variable distinction between responses that were CRs and those that were not. The contiguity independent variable was the period between CS and US onsets, or the CS-US interval. The optimal CS-US interval was found to be slightly less than a half second. In the eyelid-conditioning preparation, moreover, CS-US intervals of two seconds or more produced no conditioning at all (i.e., no increase in CS-elicited blinks as a function of paired CS-US trials), even though it could hardly be argued that the undergraduate subjects did not learn the (cognitive) "relation" between the tone and the puff that followed two seconds after the tone. Concerning the distinction between CRs and non-CRs, the CS-elicited response latency measurement was also 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. Hence, as a routine matter of scoring the data, only longer-latency blinks (the frequency of occurrence of which did increase as a function of CS-US pairings) were classified as CRs.

Influence on Other Researchers

In addition to its role in generating a body of empirical knowledge about human classical eyelid conditioning in experimental psychology, Pavlov's CR concept was also influential as a theoretical construct. The originator of American S-R behaviorism, J. B. Watson (e.g., Watson, 1913) attempted to account for all psychological learning phenomena in terms of the Pavlovian CR, being attracted by the "observable" feature of this response, in contrast with "unobservable" mental events. As Watson tackled more complex psychological functions such as thinking, the "observable" status of his explanatory constructs became more dubious. For example, his explanation of thinking was that it was due to very slight movements of the tongue, but when experimenters looked and could not observe these tongue movements, Watsonian behaviorists retorted that the tongue movements were too small to be measured.

The theoretical Pavlovian conditional response concept reappeared in the guise of the fractional anticipatory goal response in the theorizing of the S-R learning theorist Hull (1935) and Spence (1956). This hypothetical response was said to be learned through classical conditioning. It was invoked by S-R theorists from the 1930s until the 1960s to account, in S-R terms, for experimental results (mainly from "latent learning" studies) that Tolman and his S-S learning followers put forward as evidence for cognitive, sign-significate, S-S learning. Like the earlier Watsonian slight-tongue-movements construct, the testable or "observable" status of the fractional anticipatory goal response was doubtful. It was even described by one Hull-Spence S-R proponent as "incorporeal" (Moltz, 1957). A few years before this metaphysical qualifier was issued for this hypothetical Pavlovian CR, proponents of Tolman's S-S expectancy-theory position presciently complained that the construct was a deus ex machina used by S-R theorists to "smuggle" the concept of cognition into their purportedly S-R accounts (Meehl and MacCorquodale, 1953).

The decline of the S-R approach in psychology and the "paradigm shift" to the cognitive, S-S approach (Segal and Lachman, 1972) resulted in a radical change in psychologists' theoretical perspective. Consistent with the continuing "cognitive revolution" that began in the late 1960s, Pavlovian conditioning, both as a phenomenon and as an explanatory concept, is conceived in Tolman-like cognitive and purposive terms. According to R. A. Rescorla (the S-S "contingency" approach's most eminent current exponent) Pavlovian conditioning is now not just interpreted but " described [author's emphasis] 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 Tolman-like cognitive ("relations between events") and purposive ("so as to allow") formulation with the "subjective psychology" account cited above—which Pavlov opposed and which is contrary to the mechanistic accounts of conditioning proposed by S-R theorists.

The 1970s and 1980s also saw the near abandonment of the eyelid preparation as a means of studying the Pavlovian (response) conditioning phenomenon. While a more reliable form of the preparation—the rabbit nictitating membrane preparation—was developed in the 1960s, it has been used mainly 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: indeed, in the currently dominant Rescorla-Wagner (1972) model of Pavlovian conditioning, the CS-US interval 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, in line with what Pavlov characterized as "subjective psychology," is the learning of "relations between events" (i.e., cognitive, S-S learning of CS/US contingency) rather than the learning of responding (i.e., the CR) to the CS. 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 Society

Perhaps Pavlov's most important contribution to psychology was to encourage interdisciplinary research on the organism as an integrated whole. This legacy has been sustained by the Pavlovian Society, an international organization founded in the United States in 1955 by Horsley Gantt, who, as noted above, worked in Pavlov's laboratory. The official journal of this society is titled Integrative Behavioral and PhysiologicalScience. The focus "interdisciplinary research on the integrated organism" is central for the Pavlovian Society (Steinmetz, 2001). It is distinct from other contemporary scientific and scientific-professional societies in its thoroughly apolitical and unusual oesspenn to discussion and debate (Furedy, 2001). The society's motto is Pavlov's "Observation and observation!" To its members, the motto means that the issues should be debated in the light of the observed evidence, not the political loyalties of the interlocutors.

Thus, in addition to the emphasis on interdisciplinary, integrated research, Pavlov's influence today stands for open discussion and the resistance to political pressures on scientific research.

See also:CONDITIONING, CLASSICAL AND INSTRUMENTAL

Bibliography

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John J.Furedy