For more than thirty years, from 1903 until his death in early 1936, Pavlov employed “saliva drops and logic” in his quest to understand the mysteries of the human psyche.1 He organized that quest into numerous lines of investigation pursued by the scores of coworkers he directed in his physiology factory. As in earlier years, not all dogs were created equal—just as Druzhok and Zhuchka had played pivotal roles in the digestive research, so would Kal’m, Postrel, Avgust, Garsik, John, and the chimps Roza and Rafael become the heroes of research on “higher nervous activity.”
Contrary to his iconic image, Pavlov was utterly uninterested in training dogs, and very, very rarely used a bell.2 Indeed, the use of a bell was incompatible with his basic methodology, which required that the experimenter control precisely the duration and qualities of any stimulus (which is hardly possible when ringing the iconic bell with a clapper). The standard lab stimuli, accordingly, were an electronic buzzer, a harmonium, a metronome, a flashing light, and electrical shock.
The biggest problem with this iconic image, however, is that it misses the purpose and direction of Pavlov’s research, presenting as its grand achievement what was merely its point of departure. Laboring under that misunderstanding, George Bernard Shaw impatiently—and unjustly—dismissed Pavlov’s work with the quip that “Any policeman can tell you that much about a dog.” (The Russian version of this common motif among his detractors was “Every hunter knows this.”)3 Pavlov, however, always viewed his achievement as the transformation of this familiar “psychic secretion” into a reliable experimental phenomenon—the conditional reflex—and its use as a method for understanding the unseen processes in the brain that produce thoughts, emotions, and behaviors.
He was hardly the first to speculate that the behavior and psychic life of animals (and even of humans) might be the product of complex reflex reactions. René Descartes in the sixteenth century, Julien Offray de La Mettrie in the eighteenth, and Ivan Sechenov in the nineteenth were among many scientists and philosophers who had developed this notion to various degrees. Animal trainers also knew well that the judicious application of carrot and stick elicited desired behaviors from all manner of creatures. Pavlov’s Russian contemporaries Anatolii and Vladimir Durov, for example, demonstrated their animal-training techniques to rapt audiences at Moscow circuses beginning in the 1880s, explaining how they reformed animals’ instincts and reflexes to accomplish not only familiar circus tricks, but even such feats as training a cat and a mouse to live together peacefully.
The relationship between the psyche and salivation was also common knowledge long before Pavlov. In his doctoral thesis of 1904, Babkin reviewed many earlier examples in the scientific literature. French physiologist François Magendie had described in 1836 an experiment in which the mere scent of food caused a person to salivate; Bernard had described in his Leçons de physiologie expérimentale (1856) a hungry dog’s copious salivation when sniffing some cooked meat; and British, French, and German experimentalists had followed suit in subsequent decades. Charles Darwin commented in his Expression of the Emotions in Man and Animals (1872) about the inhibitory effect of fear upon salivation, and British philosopher-psychologist Alexander Bain had discussed the use of this well-known phenomenon (“dry mouth”) in India as an indication of the guilt or innocence of an accused criminal.4
Pavlov had become quite familiar with this psychic secretion during the research on digestion in the 1890s. He readily acknowledged that he could not be credited with either the idea that complex behaviors and the psyche might be analyzed as reflexes or the discovery of the conditional reflex (CR). During one of his first discussions of CRs at the Society of Russian Physicians, he associated himself with Ivan Sechenov, who, in his Reflexes of the Brain (1863), had elaborated the “brilliant” idea of analyzing psychic phenomena as reflexes. He added, however, that Sechenov was “not a genius” and had failed to develop an experimental methodology to exploit this insight. In one of Pavlov’s last essays on the subject (in 1935), he observed in the same spirit that what he had termed the “conditional reflex” had “long been visible to many [scientists]; many had paid attention to it and several had even begun to investigate it (one must mention Thorndike especially), but they had for some reason halted at the very beginning and did not elaborate knowledge of [this phenomenon] into a fundamental, essential method for the systematic physiological investigation of the higher nervous activity of the animal organism.”5
As Pavlov saw it, then, his fundamental contribution was the conversion of the CR into a reliable experimental phenomenon, its systematic investigation, and its use as an objective method for the investigation of the psyche—for exploring what he initially termed “issues of experimental psychology in animals.”6
His unvarying goal was, as he told the International Medical Congress in Madrid in 1903, to “bring the obtained objective results [of physiological experiments] to our subjective world,” to “explain the mechanism and vital meaning of that which most occupies Man—our consciousness and its torments.” As he put it in his Nobel Prize address one year later, “Only one thing in life is of essential interest for us—our psychical experience.”7 (Like most of his contemporaries, he used the word “psychical” to denote functions of the mind or psyche with no necessary reference to such things as extrasensory perception or telepathy.)
He committed himself to this quest only after envisioning a general line of march from the saliva drops that constituted his only “objective” data to an explanation of the psyche. That commitment rested upon three bedrock positions: the CR was the physiological dimension of the psychologists’ “association” (and what he had earlier termed “psychic secretion”); like all physiological processes, it was purposive, precise, and governed by deterministic relations; and its dynamics—and, therefore, those of the psychologists’ “association”—were mirrored precisely in the rate and amount of salivation during various experiments.
Pavlov’s shorthand references to this research reflected his oft-repeated claim to objectivity. In his annual reports to the IEM from 1903 to 1905, he labeled it “experimental psychology in animals,” but as his confidence and enthusiasm grew he redefined it in 1906 as “the objective investigation of the higher spheres of the central nervous system” and for the next few years as “the investigation of the activity of the large hemispheres and sense organs” before finally settling upon “the investigation of the physiology of the large hemispheres by the objective method.”8
What, precisely, did Pavlov mean by “objective”? Contrary to a common misconception, he did not mean (as did American behaviorists of his day) that he doubted the existence of the “subjective” psyche, discounted its importance, believed that scientists should focus only upon manifest behaviors, or himself proposed to ignore the subjective realm. He shared none of those positions. Nor was he so naive as to mean that his approach was devoid of theory or interpretation. Rather, for Pavlov, the objectivity of his investigations resided in two of its characteristics: that it relied upon objective, quantifiable data (saliva drops), and that he reasoned from “objective” physiological processes to “subjective” psychic phenomena. (As opposed, for example, to “subjective” psychological methodologies that reasoned from postulates about the animal’s “internal, subjective world.”)9
To understand Pavlov’s research trajectory from 1903 to 1936, we must constantly bear in mind the nature of his “objective” data (the saliva drops generated by thousands of experiments on the dynamics of CRs under various conditions) and his goal (an explanation of the “mysteries of the psyche”). The path he envisioned to get from one to the other—or, rather, to bring them together, to accomplish their “fusion” (slitie), as he expressed it—can be broken down into three basic steps. First, discover the (presumably fully determined) regularities in the salivation elicited by experiments on the formation, variation, and extinction of CRs. Second, use these regularities (patterns) to build a model of the unseen processes in the higher nervous system that produced them. Finally, use that model to explain the behavior, affect, psychological experiences, and personality of experimental animals and, ultimately, humans. In practice, these three steps proceeded in parallel over the course of three decades, with each set of conclusions constantly being revised and compelling changes in the other two.
Even this brief description of Pavlov’s trajectory reveals the great distance between the data generated by experiments and the conclusions that he sought to draw. The conceptual stretch from data to interpretive target rendered his research extremely sensitive to models and metaphors from various sources. Pavlov’s reputation as an objectivist flows from his use of quantitative measurements of salivation during thousands of varied experiments on the formation, variation, and extinction of CRs, but even a cursory look at actual lab procedures and reasoning reveals the critical role of interpretive models and metaphors, including self-consciously anthropomorphic ideas about experimental animals. For Pavlov, dogs and people were both complex machines, and therefore—and equally importantly—dogs were (relatively simple) people, and people were (relatively complex) dogs. Thus, insights into either organism (including its subjective experiences) were readily transferable to the other. Against this general background, let me sketch the general trajectory of Pavlov’s research of 1903–1936 and the consistent goals, practices, rules, language, and tensions that shaped it.
A lab dog salivates to the sound of a metronome. That dog did not do so until a CR had been established on the basis of an unconditional stimulus (US) such as food or acid. Food and acid were “unconditional” stimuli because they elicited salivation regardless of conditions. They had an inborn, purposive “business relation” (as Pavlov often put it) to salivation: saliva prepared food for passage down the esophagus and protected the mouth against possible damage by the acid. Thus food and acid elicited an unconditional reflex (UR).10 The metronome, on the other hand, was initially a neutral stimulus. Its beat did not elicit salivation, because it had no inherent “business relation” to salivation. It was transformed into a conditional stimulus (CS) by repeatedly setting the metronome beating and, in the moments just before that beat ceased, feeding the dog. (Dogs in Pavlov’s lab were fasted in advance of an experiment to assure that they were very hungry.) The power of a CS, as Pavlov’s terminology implied, was dependent upon conditions: if the metronome was now set beating in repeated trials without being paired with food, the dog responded to it with decreasing amounts of salivation—and eventually with none at all.
For Pavlov, even this simplest CR was interesting and significant because here salivation both followed the predictable, determined course expected of a physiological process and also reflected what we are accustomed to think of as a psychological process. Set a metronome beating and repeatedly accompany this with food—the dog salivates at the sound because it “expects” food to follow. Now let the metronome beat and withhold food—after a number of disappointing repetitions, the dog ceases to salivate, because it is no longer so optimistic. When Pavlov became convinced that, during experiments, these CRs originated, developed, and disappeared in a regular, determined manner, he concluded excitedly that he had found a means of generating objective data (saliva drops) about the psychological process of association. Since the CR was the physiological equivalent of this basic psychological process, investigation of CRs would reveal the mechanisms of learning, expectation, emotions, and all the other qualities that associationist psychologists attributed to associations.
This made an especially strong impression upon him because throughout his investigations of digestion in the 1890s he had thought of such salivation as “psychic secretion” and had explained its behavior in psychological, anthropomorphic terms. Dogs, he and his coworkers had come to understand, would salivate under various conditions because they “associated” those conditions with feeding and “wanted” or “expected” food. One dog would produce a voluminous psychic secretion because it was especially “passionate” or particularly “liked” the type of food with which it was being teased; another dog would not produce a psychic secretion because it was “self-possessed” and “disliked” being teased. Having invested so much psychological meaning in “psychic secretion,” Pavlov was excited at the discovery that this phenomenon, which he had previously black-boxed as an idiosyncratic process, seemed to behave in a regular, lawful, and determined manner—and so could be investigated scientifically. Only after he had established to his satisfaction that this was so—that he had converted the CR into a reliable laboratory phenomenon—did he commit himself to this new research.
The first step in Pavlov’s path from saliva drops toward the mysteries of the psyche, then, was to establish some basic regularities that governed CRs. The first such pattern involved their formation. Experimenting with a wide range of stimuli that had no inherent relation to salivation, the lab discovered that if the dog was exposed to each stimulus coincident with food or acid (the US), the animal eventually responded to the initially neutral stimulus with salivation. Experiments in the early 1900s revealed that seemingly any stimulus that acted upon the dog’s various sensory organs could become a CS—the sound of a metronome, the sight of a light or a rotating figure, the cooling of the skin, the bubbling of water, and even an electrical shock. This reinforced Pavlov’s conviction that the formation and extinction of CRs was the means by which animals obtained information about and adapted to a changing environment.
In the early 1900s, the lab established numerous other regularities. If in the same dog several different exciters were each established as a CS (say, a metronome, a flashing light, and a rotating figure), each came to act “in a completely lawful...and independent manner.”11 The dog’s response to that CS was lessened if it was exposed simultaneously to a neutral stimulus. For example, if it usually responded to the buzzer (CS) with eight drops of saliva, and that buzzer was sounded at the same time as a light flashed, the dog now produced less than eight drops of saliva. A “strong stimulus” such as a buzzer became a CS more quickly, and elicited a greater amount of salivation, than a “weak stimulus” such as a flashing light. This regularity was termed the “law of strength.” A CR could be formed to the trace of a CS. That is, when, repeatedly, a buzzer was sounded and the dog was fed only two minutes after the sound had ceased, the dog eventually salivated not at the sound of the buzzer, but only after the buzzer had been sounded and then was silent for two minutes. If one CS elicited, say, five drops of saliva, and a second CS elicited, say, four drops of saliva, the two would (in principle) elicit nine drops of saliva if the dog was exposed to them simultaneously. This became the “law of summation.”
No less important than the formation of a CR was its disappearance—“extinction,” in Pavlov’s lexicon. If the metronome (CS) was repeatedly sounded without presentation of food (the unconditional stimulus, US), its beat eventually ceased to elicit salivation. The metronome had become a “conditional inhibitor” (CI). That is, it was not merely neutral (as it had been before any experiments), but rather elicited an active inhibitory impulse. So if a CS (say, the sound of a buzzer that had been repeatedly reinforced with feeding) was paired with a CI (say, the unreinforced beating of a metronome), the combination of the two would elicit less salivation than the CS alone.
Pavlov was greatly encouraged by the discovery of these regularities, which reinforced his conviction (and the necessary precondition for this research) that the CR was a determined physiological phenomenon. Yet upon closer inspection, even these relatively simple regularities revealed complexities and variations—and so questions requiring interpretation and further research. For example, why did two dogs respond to the same CS with differing amounts of salivation? Why did it take fifteen repetitions of the metronome without reinforcement for this CS to become extinct in one dog, while it required forty-five for the same to occur in another? Given his determinist views, Pavlov saw each variation as the starting point for new experiments, for the discovery of additional laws. (For example, the different responses of various dogs to the same experiment resulted in the doctrine of nervous types, Pavlov’s objectivist term for personality and constitution.) Consequently, a number of firm conclusions reached in the early years of his research were modified or even rejected in later years—so the stages of research that I am presenting schematically here actually proceeded in parallel, constantly influencing one another.12
These studies of the CR as a phenomenon shaded seamlessly into the use of the CR as a method for Step Two—for constructing a model of the unseen nervous processes that lay behind experimental results. Pavlov’s term for these processes was “higher nervous activity.” What, exactly, transpired in the higher nervous system when a CR was formed and when it was extinguished? What were the precise mechanism and properties of the dog’s “analyzers”—his term for the unified nervous mechanism, beginning with the sensory apparatus and ending in the brain, through which the animal received information about the external world? As he pondered such questions, Pavlov developed models to explain the salivary patterns generated by increasingly complex experiments.
For example, in his lab notebook for the years just prior to World War I, Pavlov reflected about the phenomenon of “external inhibition.” This was the lab’s term for one regularity mentioned above: that a dog’s salivary response to a CS (say, the beat of a metronome) was lessened if the animal was simultaneously exposed to a neutral stimulus (say, the sound of a buzzer). If the metronome normally elicited six drops of saliva, then the metronome plus the sound of a buzzer elicited only three. Pavlov mused: “One can understand external inhibition in this way: the excited central reflex attracts to itself the nervous energy of another center, and so in this latter center, excitability declines. If this is so, then one can understand the formation of the conditional reflex in the same way—that is, the existing active center attracts to itself any excitation entering the cerebral hemispheres.”13 Here he uses a metaphor drawn from physics to visualize the unseen processes in the brain that might account for the salivary patterns observed during experiments. Similarly, when Pavlov concluded in 1912 that excitation and inhibition were both active nervous processes of equal status, he began to speak of the “attraction and collision” of excitatory and inhibitory waves in the brain. Such models—which deployed metaphors from all dimensions of his life experience—always played a central role in his design and interpretation of experiments.
Every saliva drop was presumably significant. If a stimulus elicits six drops at one moment and only four at the next, there must be a reason (some unseen nervous process, such as inhibition). Pavlov and his coworkers, however, were working on complex intact animals and were always aware of the difficulty—or impossibility—of controlling for all possible variables. As the number of experiments (and dogs) increased, so did the variance in the data, and as Pavlov’s model of the unseen processes in the brain grew increasingly complex, so did the range of possible explanations for any result. As in his digestive research, Pavlov’s research on higher nervous activity always reflected the tension between two central aspects of his scientific style, two unyielding intellectual commitments: on the one hand, to mechanistic, determinist, and precise explanations; on the other, to experimenting upon a complex, intact organism in which—as he well understood—uncontrolled variables abounded. In both areas of research, then, the interpretive moment was key.
One especially exciting and pivotal phenomenon addressed during the first decade of this research was termed “differentiation” (the physiological dimension of the psychologists’ “discrimination”). Lab studies of differentiation illustrate the dual nature of the CR as phenomenon and scientific methodology—and bring us a step closer to understanding how Pavlov thought his CR methodology might uncover the mysteries of the psyche. The basic experiment was simple. The experimenter sets a metronome beating at sixty strokes per minute and feeds the dog. After a number of repetitions, the hungry animal salivates consistently to that sound. The metronome, then, has become a CS, and a CR has been formed. The experimenter carefully measures the amount of salivation to gauge the strength of this reflex. She then slows the metronome to forty beats per minute—and does not feed the dog after it sounds. Initially, the dog salivates to the sound of this slower beat, but after a number of repetitions ceases to do so. In Pavlovian notation: M60 has remained a CS (in lab shorthand, it was M+), but M40 has become a CI (M−).
Many different lines of investigation flowed from this simple experiment. In one ingenious series of trials, Pavlov and his coworkers used the phenomenon of differentiation as an experimental method for ascertaining the sensory capacities of the dog’s analyzers. For example: How acute is a dog’s sense of time? (To appreciate the difficulty of this question, imagine trying to answer this question for a pet.) Clearly, if the dog salivates to M60 (the CS) but not to M40 (the CI), it can differentiate between those two speeds. So now the experimenter speeds up the metronome to M50 and does not reinforce this with feeding. She alternates this unreinforced speed with M60, which she continues to accompany with food. If the dog successfully differentiates between M60 and M50, the gap between the CS and the CI can be progressively narrowed until the limit of the dog’s acuity is established. Pavlov and his coworkers concluded that a dog can distinguish between the beat of a metronome at 96 and 104 beats per minute—that is, between intervals of 1/43 of a second. In the years before the Great War, they used this same method to determine the acuity of the dog’s various analyzers—its ability to distinguish among colors, distances, temperatures, shapes, and different points on its body.14
Differentiation experiments also contributed to the lab’s developing model of higher nervous processes. For example: Why, just after M60 was established as a CS, did the beating of the metronome at any speed initially elicit salivation? And why, after a series of repetitions during which only M60 was reinforced with feeding, did the dog cease to salivate in response to any speed other than M60? Pavlov concluded that any stimulus initially “irradiates” across the entire cerebral cortex—leading to general excitation—and only then, in a second phase, “concentrates” at one particular point. He also reasoned that the process of differentiation resulted from “the struggle and collision” of the two basic nervous processes—excitation and inhibition. Thus, the beating of the reinforced M60 excited the entire cerebral cortex, but after a series of trials in which other speeds were not reinforced by feeding, each of these other speeds became CIs and generated an inhibitory wave that suppressed excitation at all speeds other than M60. The ability of the dog to differentiate between M60 and M40, then—to respond to the former with salivation and the latter with none—depended (according to lab doctrine by the 1910s) upon the interplay and balance of its excitatory and inhibitory processes.15
This is only one example of the manner in which Pavlov and his collaborators constructed a model of the unseen processes in the brain that might explain the salivary patterns generated by their experiments. (Decades later, Canadian psychologist Donald Hebb coined a pithy term for this kind of model, referring to it as a “conceptual nervous system.”) Pavlov’s model became increasingly complex and ramified over the years—featuring such processes as excitation, several types of inhibition, disinhibition, irradiation, and concentration—as it developed to encompass the (inevitably) disparate data from thousands of increasingly complex experiments in which every drop of saliva was assumed to have a mechanistic, determinist explanation.16
In his attempt to move from the salivary patterns generated by CR experiments to the mysteries of the psyche, Pavlov has now taken two steps: he has identified numerous regularities in the formation, variation, and extinction of CRs, and he has used the salivary patterns during experiments to construct a model of higher nervous processes. The final, climactic step—one that is most discordant with Pavlov mythology—was to use that model to explain the psychological experiences and affect of his experimental animals (and, ultimately, of humans).
Pavlov was certainly interested in behavior (a term that acquired almost as many varied meanings as the word “objective”), but he was not a behaviorist. Unlike John Watson and other American behaviorists of his day, he consistently acknowledged the existence and paramount importance of subjective phenomena—of the internal emotional and intellectual experiences of humans and other animals—and he always believed that science should seek to explain them. As an evolutionist, Pavlov (like Darwin) never doubted that dogs were conscious beings with thoughts and emotions, and that there were important continuities between a dog’s anger or grief and those same emotions in humans. This belief had been reinforced by years of experience in the 1890s with the intact “normal and happy” dogs in his lab—dogs that all had recognizable personalities, tastes, and moods. One coworker later recalled the chief’s spontaneous reaction when an experimental dog “ran happily into the room in anticipation of the pleasure of sham-feeding.” Pavlov “petted and stroked the dog and said more than once, ‘and where did people get it into their heads that there is a qualitative difference between us and animals? Do this dog’s eyes not sparkle with joy? Why not investigate the phenomenon of joy in the dog; here it is much more elementary and therefore accessible.’”17 Similarly, in the 1930s—when he was experimenting with the chimps Roza and Rafael—he had no doubt that “the chimp is thinking,” and even identified “elements of scientific creativity” in its mental processes. When Rafael made elementary errors, Pavlov derided him as a “fool” and a “ninny.”18
Pavlov was not a philosopher, and he was uncomfortable with explicitly philosophical discourse (at least in official settings). He was most confident when interpreting experimental data, operating implicitly on the rough-and-ready mechanical materialism that he had imbibed in the 1860s. He was, however, acutely aware of philosophical discussions about the complexity of relating physiological processes to psychological phenomena and experiences. In publications for Western audiences, or when challenged by a philosopher or psychologist, he usually fell back upon Bernardian, positivist rhetoric about scientific methodology: whatever the ultimate relationship between brain and psyche, he would argue, the only truly scientific approach to that relationship was to accumulate objective knowledge about higher nervous processes. The data would eventually resolve loftier theoretical issues.
So, for example, in the introductory portion of a speech of 1906 delivered in London to honor T. H. Huxley, he seemed to disavow any interest in “so-called psychical processes,” putting these beyond the purview of scientific method. “Were the investigator to speak of the psychical faculties of the higher animals,” he commented, “he would be transferring ideas from his own inner world to nature.” The true scientist “must consider only one thing: what is the relation of this or that external reaction of the animal to the phenomena of the external world?”19 A listener might easily have thought that Pavlov was limiting himself to what I have characterized as Steps 1 and 2 in his scientific mission. Yet in the conclusion to that same speech, he also posed the question: what is the relationship between these physiological processes and “psychological facts”? Exploration of that relationship, he hinted, was on his agenda—but it remained premature:
However interesting that relationship is even now, one must admit that physiology does not have a serious occasion to address it. Its immediate task is to collect, systematize, and analyze the endless object material that presents itself. But it is clear that in the future, physiology will be in a position, to a significant degree, to provide a true resolution of those agonizing tasks that from time immemorial have occupied and tormented the human being. Man will acquire incalculable advantages and extraordinary power over himself when the scientist has subjected his fellow human to the very same external analysis as with every object of nature, when the human mind will look at itself not from within but from without. 20
Pavlov’s rhetoric, then, sometimes seemed to ally him with behaviorism, but Step 3—the use of his model of higher nervous processes to confront the subjective world itself—was always on his agenda.
Similarly, during a lively exchange with philosophers and psychologists at St. Petersburg’s Philosophical Society in 1916, he conceded that “The relationship between nervous phenomena and the subjective world is quite complex. To move from one to the other is very difficult.” He knew little, he admitted, about the various theories concerning this relationship. Nor did he need to master them: “I have always limited myself only to practice, methods. I cannot agree that my approach represents pure materialism. I am only pursuing an approach useful for investigation.” The accumulation of facts over time would itself illuminate the actual relationship between nervous processes and the subjective world.21A similarly careful positivist stance dominates Pavlov’s two books about CRs—books that he knew would be read by specialists from various disciplines and that he self-consciously aimed at the American behaviorists who, he thought, constituted his most likely allies in psychology.
Privately, however, he did reflect about the relationship between physiological processes and psychological experiences, and in unthreatening settings was much more forthcoming about his thoughts. In the early 1900s, he briefly participated in a study group with his assistants Orbeli and Zelenyi that addressed philosophical theories about the relationship of mind and body. (Orbeli and Zelenyi both held fashionable neo-Kantian positions on the parallelism of physiological and psychological processes, and expressed these views in their doctoral theses.) Pavlov soon wearied of these discussions and quit, explaining that he preferred to “study the factual aspect” of the question.22
Yet he continued to worry about the philosophical problem of integrating the physiological and psychological realms. Sometime around 1912, for example, he jotted the following in his pocket notebook: “We consider all so-called psychic activity to be a function of the brain mass, of a defined mechanism, that is, of an object conceived spatially. But how can one place upon this mechanism an activity that is conceived psychologically, that is, nonspatially?”23
As his model of higher nervous processes grew richer—and, especially, after exciting experimental results in 1911–1913 convinced him that he was indeed on the road to a grand physiology of mind and emotion 24—Pavlov expressed his views about the integration of the objective and subjective realms more frequently in informal conversations in the lab and in comments to unintimidating audiences such as the doctors of the Society of Russian Physicians and the general public. These views were also built into everyday lab procedures. Essentially, he came to look for parallels between the higher nervous processes transpiring (according to his model) during CR experiments, on the one hand, and the behavior, affect, and personality of experimental animals, on the other, and to explain the latter as the expression of the former. Cowardice was the result of chronic overinhibition, negativism was the psychological expression of the “ultra-paradoxical phase” in higher nervous activity (during which a CS produced an inhibitory response, and a CI produced an excitatory response), and so forth.25
Another central feature of the Pavlov mythology, then, is simply false—that he avoided subjective or anthropomorphic descriptions of experimental animals and banished these from his lab. That was partially true only for a brief transitional period. In the early 1900s, Pavlov replaced a series of psychological terms with physiological ones (for example, “teasing” became “excitation at a distance,” “psychic” became “complex nervous,” and “pain” became “destructive irritation”), and in public settings criticized and forswore the use of “subjective” terms. Once he became confident that he had established a physiological lexicon and model of higher nervous processes through which he could explain the dog’s affect and behavior, however, subjective, anthropomorphic descriptions of laboratory dogs became central to his research. Maria Petrova, Pavlov’s closest collaborator during the last two decades of his life, recalled that as his research matured and he grew more confident, “he ceased to fear psychological terms, since he felt the strength to call them to battle, to confront a new reality, and through this confrontation to discover the path of further work. The goal of the entire enterprise was revealed at the moment when victory was assured and the unity of the system became obvious to all.”26 For Pavlov, that overriding goal was to map his understanding of higher nervous processes upon everyday psychological experiences, and to accomplish in this way the conceptual integration of objective processes and subjective experiences. To do so, he and his coworkers needed to use common psychological characterizations—for these constituted the ultimate explanatory target of their investigations.
Speaking informally in later years, he put this bluntly: “It would be stupid to reject the subjective world. It clearly exists, of course. Psychology, as a formulation of the phenomena of our subjective world, is an entirely legitimate thing and it would be blind to quarrel with it. Our actions, all forms of social and personal life are formed on this basis.... The question is how to analyze this subjective world.” His opinion of psychology as a discipline fluctuated over the years, but he never wavered in his conviction that the subjective realm existed, that it was of paramount importance, and that his approach was the most fruitful way to investigate it—and so to create a truly scientific psychology.27
The lab’s experimental protocols clearly reflected his commitment to integrating the objective and subjective realms. As research took off and Pavlov standardized the form of experimental notations, coworkers were enjoined to record not only the time of the trial, the nature of the exciter used, and the amount of salivation generated, but also, in a final column, “other observations.” These routinely included such information as: the dog “ate greedily,” “reacted defensively” (or “aggressively”), “exhibited negativism,” or “sighed.” By the early 1920s, when each dog was characterized according to its nervous type, dogs were routinely described with such terms as “cowardly” or “brave.”
Anthropomorphic metaphors were always central to Pavlov’s thinking. We will examine this in detail in future chapters, so I offer here just a few illustrative examples. In 1915, coworker Max Gubergritz noticed that, during these experiments, the chief frequently compared the experimental animals “with characters from literature, especially from the works of his favorite writers.”28 In Pavlov’s public lecture of 1918 “On the Russian Mind,” he observed that in the bird cage at the St. Petersburg zoo he had “been struck by the variety of characters and types represented by its inhabitants. Among the various sorts of small birds there passed before me literally all the types in Gogol’s Dead Souls.” One week later, in his speech “On the Foundations of Culture of Animals and Man,” he drew upon his understanding of higher nervous processes to explain the varied responses to experiments of “cultivated,” “pragmatic,” and “muddled” dogs—and then extended this analysis to explain the national characteristics of various peoples: the stellar contributions of the Germans and English to science, the chronic disorder in Russia’s schools, the Russian Revolution, and even Trotsky’s ludicrous negotiating position during the peace talks at Brest-Litovsk.29
In his weekly discussions with coworkers in the 1930s, Pavlov explicitly and self-confidently employed subjective anthropomorphic language to discuss the responses of experimental animals. For example, in April 1930 he speculated about one dog’s response to two conditional stimuli: “The tone that signaled food...was pleasant for [the dog] and it was prepared to listen to it for a long time, and so did not hurry to eat. The [other] tone, which reminded it of the destructive exciter [this tone had been paired with an electrical shock], was unpleasant for it, so it rapidly hurried to the food so that eating would inhibit this unpleasant sensation.” He then reminisced about the early days of CR research, when he had fined workers for employing precisely such a “psychological interpretation of the facts.” At that time, he explained, this strict policy had been necessary because such interpretations would only have caused confusion. “But now,” the transcript of this meeting continued, “Ivan Petrovich frequently employs a subjective interpretation of the phenomena he observes because, due to his thirty years of experience studying higher nervous activity, he is always able to link subjective reasoning with the corresponding objective facts, and this way of thinking helps him more easily understand phenomena.” Coworkers should not follow suit, for it might easily lead them to confusion, “but he considers incorrect the thinking of those scientists who attempt to completely ignore the subjective world—since this world is, after all, closer to us than anything else, because we live in it.”30
For Pavlov, the subjective world of the dog was understandable both as a function of his model of higher nervous processes and—though he would never have referred to it this way—through introspection. He confided to one journalist, “That which I see in dogs I immediately transfer to myself, since, you know, the basics are identical.” Investigations of one particular dog, Garsik, even helped Pavlov solve for himself the mystery of how such an excitable, choleric fellow as he—apparently lacking the necessary balance of excitation and inhibition necessary for cognition of reality—nevertheless became a fine scientist.31 Conversely, seat-of-the-pants introspection regularly informed perceptions of experimental dogs. “The circumstance that our animals cannot tell us about their experiences,” Pavlov explained more than once, “is no loss for an understanding of their state, and if they were able to speak they would probably not be able to add anything. One can propose that during a break toward excitation [that is, when the dog is chronically overexcited] the animal would report that it could not restrain itself from doing what it shouldn’t, and during a break toward inhibition the animal would say that it could not do that which it must necessarily do.”32
A passage in Pavlov’s lab notebook for the early 1930s captures the centrality of anthropomorphic thinking in his methodology and goal. Pondering the responses of the experimental dog Pingel’, he observed: “A Napoleonic type. When free [that is, when not strapped to the experimental stand]—extremely mobile and greedy. In the stand—very peaceful, almost motionless, a small and inconstant secretory reaction to conditional stimuli; a positive movement reaction (to food) is almost absent. Approaches the food trough haltingly and in a demonstratively very slow manner. Then eats greedily, and licks its chops for a very long time, even licking its feet.”33 The goal of his grand quest was to understand the higher nervous processes that produced this greedy, aggressive, and crafty Napoleonic creature—and, by extension, Napoleon himself.
Pavlov’s holy grail, then, was the conceptual integration of physiological and psychological phenomena, an integration that he attempted to accomplish by identifying patterns in the formation, variation, and extinction of CRs; by developing a conceptual model of the higher nervous processes that generated those patterns; and by using that model (laden with various metaphors) to explain behaviors, personalities, and various subjective states. The fundamental criterion of a successful explanation remained the same as in his digestive research—not, of course, complete knowledge of his subject (which he considered impossible as a matter of principle), but the ability to encompass, contain, and so explain his experimental data by a limited number of basic principles. As he put it, he aimed to “reduce an innumerable mass of various separate phenomena to a lesser number of general basic phenomena.”34
This quest set him on a three-decade journey to the horizon. He discovered much of interest along the way—facts, methodologies, relationships, and insights of enduring value—but the ultimate destination continually receded behind an endless landscape of new and perplexing complexities. Pavlov was frequently excited and heartened by experiments that produced satisfyingly consistent results, by surprising discoveries, by the development of new and powerful explanatory principles, by the revelation of new research perspectives, and by indications that his research might have clinical value (for example, in the analysis and treatment of mental illness). Yet he was also continually disheartened, even depressed, as the much-trumpeted results and interpretations of earlier experiments were overturned and apparently solid ground dissolved, as the experimental data (and so the psyche) failed to conform to even increasingly elaborate mechanistic models.
In this sense, his experience with CR research differed sharply from that earlier with digestion. He had completed his Lectures on the Work of the Main Digestive Glands (1897) after about seven years of intensive research; elegantly composed and enthusiastically argued, it had left him with a sense of intellectual closure and triumph. He would complete his single monograph on CRs, Lectures on the Work of the Large Hemispheres of the Brain (1927), only after numerous failed attempts and more than twenty years of research (with far greater resources). Composed reluctantly and lacking the elegance and clear argumentation of his earlier book, it left him consumed by what he termed “the Beast of Doubt.”
Pavlov always responded to his doubts with new experiments—and a single encouraging result sufficed to restore his enthusiasm and confidence. The journey was long, but surely he was on the right path! But therein resided the paradox of his quest: in true positivist spirit, he was convinced that the more experiments he and his coworkers conducted, the more facts they collected, and the more patterns they were therefore able to establish, the closer he would come to his goal. The data from experimental trials would reveal a set of basic laws and a model of higher nervous activity that would, in turn, explain the behavior, personality, and affect of his dogs and, eventually, humans. He expressed this methodological faith simply in a conversation with one coworker about lab research on the central, and vexing, question of the dynamics of excitation and inhibition: “We elicit various conditions under which the excitatory and inhibitory processes manifest themselves. Everything comes down to this. The time will come—and it will be such a wonderful moment—when suddenly everything becomes clear, when we will know precisely all the conditions that elicit the process and weaken it.”35
Yet just the opposite proved true. Over the years, as his lab enterprise expanded and the number of coworkers, dogs, and experiments swelled, the resultant avalanche of data overwhelmed and defeated his every attempt at systematization. Experimental results simply would not fit snugly into even the most imaginative framework. More experiments, in other words, just compounded the problem.
Pavlov’s interpretive response to these confounding junctures was always the same: to enlarge the explanatory frame by introducing a new variable that might resolve discrepancies. This was a quintessentially Bernardian response to contradictory data: determinism presumably reigned, so varied results to the same experiment testified to the existence of some uncontrolled variable. Pavlov thought in broad biological terms about CRs and the nervous system in general, viewing them as means through which organisms maintained balance both as an integrated whole and in relationship to a changing environment. Constantly imagining the dog in his experimental stand as an animal (or human) in nature and society, he regularly introduced new variables from the broader world beyond the lab. Enriched by these new variables, his explanations continually expanded in scope at the cost of precision and refutability.
This process defined the underlying logic of Pavlov’s investigations as they unfolded over three decades, and imparted power, paradox, and pathos to his scientific quest. The five “basic principles” through which he attempted unsuccessfully to contain his experimental data when he first tried to write a monograph on CRs from 1917 to 1921 expanded constantly over subsequent years. For example, the fact that different dogs required differing numbers of trials to form and extinguish CRs—combined with their observably different personalities—gave rise in the 1920s to the doctrine of nervous types. Delineation of the various nervous types would, presumably, explain the varied responses of different dogs to the same experiment. Yet experiments designed to establish a typology continually revealed more discrepancies and more variables, so the number of differing nervous types grew from three to more than twenty-five. And still the data was not contained, nor did the results of CR experiments map neatly onto his animals’ personalities. His attempt to encompass contradictory data through new variables drawn from a broader biological and social perspective generated new “basic principles” and lines of investigation on the relationship between excitation and inhibition, the phases of hypnosis and sleep, the interplay of nature and nurture, mental illness in dogs and humans, and the analytical and synthetic qualities of the cortex. Each expansion of the interpretive frame produced interesting and valuable observations and insights, each revealed new perspectives that excited the chief and urged him on, and each failed to bring him and his companions any closer to the horizon.36
Pavlov’s enthusiasm for this quest remained undiminished to the end. During his final months, he was enlarging the frame again: eagerly awaiting the results of a breeding experiment designed to clarify the roles of heredity and environment and so answer vexing questions about nervous types, revising his definition of the conditional reflex to accommodate experimental data on chimps and humans, and extending his doctrine to encompass the insights of Gestalt psychology. Surely, he mused just before his death, if he could live just another five years, he would witness the decisive triumph of his “scientific mission.”