As a college student, B. F. Skinner gave little thought to psychology. He had hoped to become a novelist, and majored in English. Then, in 1927, when he was twenty-three, he read an essay by H. G. Wells about the Russian physiologist Ivan Pavlov. The piece, which appeared in the Times Magazine, was ostensibly a review of the English translation of Pavlov’s “Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex.” But, as Wells pointed out, it was “not an easy book to read,” and he didn’t spend much time on it. Instead, Wells described Pavlov, whose systematic approach to physiology had revolutionized the study of medicine, as “a star which lights the world, shining down a vista hitherto unexplored.”

That unexplored world was the mechanics of the human brain. Pavlov had noticed, in his research on the digestive system of dogs, that they drooled as soon as they saw the white lab coats of the people who fed them. They didn’t need to see, let alone taste, the food in order to react physically. Dogs naturally drooled when fed: that was, in Pavlov’s terms, an “unconditional” reflex. When they drooled in response to a sight or sound that was associated with food by mere happenstance, a “conditional reflex” (to a “conditional stimulus”) had been created. Pavlov had formulated a basic psychological principle—one that also applied to human beings—and discovered an objective way to measure how it worked.

Skinner was enthralled. Two years after reading the Times Magazine piece, he attended a lecture that Pavlov delivered at Harvard and obtained a signed picture, which adorned his office wall for the rest of his life. Skinner and other behaviorists often spoke of their debt to Pavlov, particularly to his view that free will was an illusion, and that the study of human behavior could be reduced to the analysis of observable, quantifiable events and actions.

But Pavlov never held such views, according to “Ivan Pavlov: A Russian Life in Science” (Oxford), an exhaustive new biography by Daniel P. Todes, a professor of the history of medicine at Johns Hopkins School of Medicine. In fact, much of what we thought we knew about Pavlov has been based on bad translations and basic misconceptions. That begins with the popular image of a dog slavering at the ringing of a bell. Pavlov “never trained a dog to salivate to the sound of a bell,” Todes writes. “Indeed, the iconic bell would have proven totally useless to his real goal, which required precise control over the quality and duration of stimuli (he most frequently employed a metronome, a harmonium, a buzzer, and electric shock).”

Pavlov is perhaps best known for introducing the idea of the conditioned reflex, although Todes notes that he never used that term. It was a bad translation of the Russian uslovnyi, or “conditional,” reflex. For Pavlov, the emphasis fell on the contingent, provisional nature of the association—which enlisted other reflexes he believed to be natural and unvarying. Drawing upon the brain science of the day, Pavlov understood conditional reflexes to involve a connection between a point in the brain’s subcortex, which supported instincts, and a point in its cortex, where associations were built. Such conjectures about brain circuitry were anathema to the behaviorists, who were inclined to view the mind as a black box. Nothing mattered, in their view, that could not be observed and measured. Pavlov never subscribed to that theory, or shared their disregard for subjective experience. He considered human psychology to be “one of the last secrets of life,” and hoped that rigorous scientific inquiry could illuminate “the mechanism and vital meaning of that which most occupied Man—our consciousness and its torments.” Of course, the inquiry had to start somewhere. Pavlov believed that it started with data, and he found that data in the saliva of dogs.

Pavlov’s research originally had little to do with psychology; it focussed on the ways in which eating excited salivary, gastric, and pancreatic secretions. To do that, he developed a system of “sham” feeding. Pavlov would remove a dog’s esophagus and create an opening, a fistula, in the animal’s throat, so that, no matter how much the dog ate, the food would fall out and never make it to the stomach. By creating additional fistulas along the digestive system and collecting the various secretions, he could measure their quantity and chemical properties in great detail. That research won him the 1904 Nobel Prize in Physiology or Medicine. But a dog’s drool turned out to be even more meaningful than he had first imagined: it pointed to a new way to study the mind, learning, and human behavior.

“Essentially, only one thing in life is of real interest to us—our psychical experience,” he said in his Nobel address. “Its mechanism, however, was and still is shrouded in profound obscurity. All human resources—art, religion, literature, philosophy, and the historical sciences—all have joined in the attempt to throw light upon this darkness. But humanity has at its disposal yet another powerful resource—natural science with its strict objective methods.”

Pavlov had become a spokesman for the scientific method, but he was not averse to generalizing from his results. “That which I see in dogs,” he told a journalist, “I immediately transfer to myself, since, you know, the basics are identical.”

Ivan Pavlov was born in 1849 in the provincial Russian city of Ryazan, the first of ten children. As the son of a priest, he attended church schools and the theological seminary. But he struggled with religion from an early age and, in 1869, left the seminary to study physiology and chemistry at St. Petersburg University. His father was furious, but Pavlov was undeterred. He never felt comfortable with his parents—or, as this biography makes clear, with almost anyone else. Not long after “The Brothers Karamazov” was published, Pavlov confessed to his future wife, Seraphima Vasilievna Karchevskaya, who was a friend of Dostoyevsky’s, that he identified with the rationalist Ivan Karamazov, whose brutal skepticism condemned him, as Todes notes, to nihilism and breakdown. “The more I read, the more uneasy my heart became,” Pavlov wrote in a letter to Karchevskaya. “Say what you will, but he bears a great resemblance to your tender and loving admirer.”

Pavlov entered the intellectual world of St. Petersburg at an ideal moment for a man eager to explore the rules that govern the material world. The tsar had freed the serfs in 1861, helping to push Russia into the convulsive century that followed. Darwin’s theory of evolution was starting to reverberate across Europe. Science began to matter in Russia in a way it hadn’t before. At the university, Pavlov’s freshman class in inorganic chemistry was taught by Dmitri Mendeleev, who, a year earlier, had created the periodic table of the elements as a teaching tool. The Soviets would soon assign religion to the dustbin of history, but Pavlov got there ahead of them. For him, there was no religion except the truth. “It is for me a kind of God, before whom I reveal everything, before whom I discard wretched worldly vanity,” he wrote. “I always think to base my virtue, my pride, upon the attempt, the wish for truth, even if I cannot attain it.” One day, while walking to his lab at the Institute for Experimental Medicine, Pavlov watched with amazement as a medical student stopped in front of a church and crossed himself. “Think about it!” Pavlov told his colleagues. “A naturalist, a physician, but he prays like an old woman in an almshouse!”