Behavioral psychology formally started in 1913, when John B. Watson published “Psychology as the Behaviorist Views It,” a paper now widely known as the “behaviorist manifesto.” But the ideas behind it had been building for over a decade before that, and the school of thought continued evolving for decades after. The full story stretches from the 1890s through the 1950s, when behaviorism dominated American psychology before giving way to the cognitive revolution.
The Roots: Pavlov and Thorndike in the 1890s and 1900s
Before anyone used the word “behaviorism,” two researchers were already doing the kind of work that would define it. In Russia, Ivan Pavlov was studying digestion in dogs when he noticed something odd: the dogs started salivating not just when food appeared, but when they heard the footsteps of the person who usually fed them. This led Pavlov to systematically study what he called the “conditional reflex,” the idea that animals could learn to associate one stimulus with another. His initial results were presented at the International Congress of Medicine in Madrid in 1903.
Pavlov’s work was essentially unknown in the United States until 1906, when a lecture of his was published in the journal Science. But even before American psychologists heard about Pavlov, Edward Thorndike was running his own experiments. In 1898, Thorndike published his doctoral dissertation on animal intelligence, based on placing cats inside “puzzle boxes.” Each box had a latch the cat needed to operate to escape and reach food outside. The key finding was simple but powerful: with repeated trials, the cats escaped faster and faster. They were learning from results.
Thorndike didn’t formally name his principle until 1911, when he called it the Law of Effect. The idea was that behaviors followed by satisfaction become more firmly connected to the situation that produced them, while behaviors followed by discomfort become weaker. This was a radical shift for psychology. Instead of trying to examine what an animal was thinking or feeling, Thorndike focused entirely on what it did and what happened next. That emphasis on observable behavior and measurable outcomes laid the groundwork for everything Watson would argue a few years later.
Watson’s 1913 Manifesto
John B. Watson, a professor at Johns Hopkins University, drew a hard line in 1913. In his paper “Psychology as the Behaviorist Views It,” he argued that psychology should stop trying to study consciousness, introspection, and mental states. If psychology wanted to be a real natural science, on par with chemistry or physics, it needed to focus exclusively on observable behavior. Thoughts and feelings, Watson insisted, were not things a scientist could measure reliably. Behavior was.
Watson didn’t just want psychology to change its methods. He wanted the field to change its purpose. He argued that empirical data and principles generated by this new science had to be applied to solving human and social problems to have real meaning. Psychology should predict and control behavior, not speculate about the inner workings of the mind. This was the founding statement of behaviorism as a formal discipline.
Watson quickly became one of the most visible psychologists in America. In 1915, his presidential address to the American Psychological Association was titled “The Place of the Conditioned Reflex in Psychology,” championing Pavlov’s classical conditioning as a core research tool. By this point, Watson had successfully bridged the Russian physiological research and American psychology into a single framework.
The Little Albert Experiment
In 1920, Watson and his graduate student Rosalie Rayner conducted one of psychology’s most famous (and controversial) experiments. They attempted to condition a phobia in a young infant they called “Albert B.” The goal was to demonstrate that emotional responses, specifically fear, could be created through the same conditioning process Pavlov had used with dogs. By pairing a white rat with a sudden loud noise, Watson and Rayner showed that the infant began to cry and withdraw from the rat alone, even without the noise.
The experiment was significant not for its rigor (by modern standards, it had serious ethical and methodological problems) but for what it represented. Watson was arguing that even something as seemingly innate as fear could be explained through learning and environmental conditioning, with no need to invoke instinct, unconscious drives, or mental states. This was behaviorism applied to human emotion, and it captured enormous public attention.
Skinner and Operant Conditioning
B.F. Skinner took behaviorism in a new direction starting in the 1930s. Where Pavlov and Watson had focused on reflexive responses triggered by stimuli, Skinner was interested in voluntary behavior: actions an organism performs because of what happens afterward. He called this “operant behavior,” meaning behavior controlled by its consequences.
Skinner designed a simple but ingenious apparatus, now called the Skinner box, to study this. A hungry rat or pigeon was placed inside a chamber with a lever (for rats) or an illuminated disk to peck (for pigeons). When the animal performed the correct action, it received food. Skinner could then systematically vary when and how often food was delivered, creating different “reinforcement schedules.” Some schedules rewarded every correct response. Others rewarded only after a certain number of responses, or after a set amount of time had passed.
These experiments revealed remarkably consistent patterns of behavior. Animals responded differently depending on the schedule of reinforcement, and these patterns were predictable and repeatable. Skinner also explored conditioned reinforcement, the idea that a stimulus paired with a primary reward (like food) can itself become rewarding. This concept helped explain more complex chains of behavior in everyday life.
Skinner became the most influential behaviorist of the mid-twentieth century, extending his ideas to language, education, and social behavior. His 1957 book Verbal Behavior attempted to explain all of human language through operant conditioning principles.
Behaviorism’s Peak and Decline
From roughly the 1920s through the 1950s, behaviorism was the dominant force in American psychology. University departments, research funding, and textbooks were organized around its principles. It never took as strong a hold in Europe, but in the United States it was essentially the mainstream.
The shift started in the late 1950s, driven less by internal dissent than by breakthroughs in fields outside psychology. In 1948, Claude Shannon published his foundational paper on information theory, which gave scientists a mathematical framework for thinking about how information is transmitted and processed. In 1956, George Miller published research showing that the limits of short-term memory followed patterns that couldn’t be explained by behaviorist principles alone. That same year, Allen Newell, J.C. Shaw, and Herbert Simon built a computer program that could solve logic problems, suggesting that mental processes could be modeled and studied scientifically after all.
The sharpest blow came from linguistics. In 1957, Noam Chomsky published Syntactic Structures, arguing that the structure of human language was too complex and too universal to be explained by reinforcement alone. Two years later, Chomsky published a devastating review of Skinner’s Verbal Behavior, arguing point by point that operant conditioning could not account for how children learn language. By the early 1960s, behaviorism was on the wane in academic departments across America, replaced by what is now called the cognitive revolution.
Behaviorism’s Lasting Influence
Behaviorism’s dominance lasted roughly four decades, but its influence didn’t disappear when cognitive psychology took over. The core techniques Skinner developed remain the foundation of applied behavior analysis, which is widely used in treating autism spectrum disorder, managing classroom behavior, and training animals. Cognitive behavioral therapy, one of the most evidence-supported forms of psychotherapy, is built on a hybrid of behavioral and cognitive principles. Exposure therapy for phobias still works on essentially the same logic Watson demonstrated in 1920: if a fear can be learned through association, it can be unlearned the same way.
The timeline, then, runs from Thorndike’s puzzle boxes in 1898 through Watson’s 1913 manifesto (the official founding), Skinner’s operant conditioning work from the 1930s onward, and behaviorism’s gradual displacement by cognitive psychology in the late 1950s and early 1960s. The formal answer is 1913, but the intellectual roots go back at least fifteen years earlier, and the practical legacy is still very much alive.