B. F. Skinner

Who was B. F. Skinner?

Skinner grew up in a small railroad town in northeastern Pennsylvania, the son of a lawyer, and spent his boyhood building things — wagons, rafts, a perpetual-motion machine that did not work. He went to Hamilton College intending to become a writer, and after graduating with a degree in English in 1926 he tried. Robert Frost had read three of his short stories and sent an encouraging letter. A year in his parents' house produced almost nothing, and Skinner later concluded that he had failed as a writer because he had nothing important to say. He decided that literature described behavior and that science might explain it.^[2]

What pushed him toward psychology was reading: John B. Watson's Behaviorism, Bertrand Russell's essays on Watson, and Ivan Pavlov's Conditioned Reflexes, newly translated into English in 1927. He entered Harvard's graduate program in 1928 with no formal training in the subject, worked largely in the physiology laboratory of William Crozier, and set himself a schedule of study so strict that he later described it with some embarrassment. By 1931 he had a PhD; by 1938 he had a book that defined a new field.^[3]

The thread running through everything he did afterward is a single ambition: to make psychology a natural science of behavior, with the same standing as physics or biology, by finding orderly relationships between what an organism does and the conditions under which it does it — without appealing to a mind inside to do the explaining.

B. F. Skinner's life and career: a timeline

• 1904

  Born in Susquehanna, Pennsylvania

  March 20. His father, William, was a lawyer; his mother, Grace, gave him her maiden name, Burrhus. Friends and family called him Fred.

• 1926

  Hamilton College, then the "dark year"

  Graduates with a BA in English. Spends a year at home in Scranton trying to write fiction, then a few months in Greenwich Village. Reads Watson, Pavlov, and Russell, and decides to become a psychologist.^[2]

• 1928–1931

  Harvard graduate school

  Builds his own apparatus — a series of increasingly automated boxes for studying rats' eating and lever-pressing — and, almost by accident, the cumulative recorder. Completes his PhD in 1931 with a thesis on the concept of the reflex.^[3]

• 1933–1936

  Harvard Society of Fellows

  One of the first Junior Fellows of the newly founded Society, which gives him three years to do research with no teaching duties. In 1935 he publishes the paper distinguishing two types of conditioned reflex that will lead to the word "operant."^[4]

• 1936

  University of Minnesota

  Takes his first faculty post. Marries Yvonne (Eve) Blue the same year. Daughter Julie is born in 1938; Deborah in 1944.

• 1937

  "Operant" and "respondent"

  In a reply to the Polish physiologists Konorski and Miller, Skinner introduces the terms that separate behavior emitted and controlled by its consequences from reflexive behavior elicited by a prior stimulus.^[5]

• 1938

  The Behavior of Organisms

  His first book lays out the experimental analysis of behavior: rate of response as the basic datum, reinforcement, extinction, discrimination, and the first schedule effects, all from rats in his apparatus.^[6]

• 1940–1944

  Project Pigeon

  Trains pigeons to guide a missile by pecking at a target image projected inside its nose cone. The birds worked; the military, committed to radar and electronic guidance, canceled the project in 1944. Along the way, in 1943, Skinner and his collaborators discover shaping while teaching a pigeon to "bowl."^[7][8]

• 1945

  Indiana, the air crib, and radical behaviorism

  Becomes chair of psychology at Indiana University. Publishes "Baby in a Box" in Ladies' Home Journal describing the climate-controlled crib he built for Deborah, and "The Operational Analysis of Psychological Terms," the founding statement of radical behaviorism.^[9][10]

• 1948

  Back to Harvard; Walden Two; superstition

  Returns to Harvard, where he stays for the rest of his career. Publishes the utopian novel Walden Two, written in seven weeks in 1945, and the "superstition in the pigeon" experiment.^[11]

• 1953

  Science and Human Behavior and the teaching machine

  Extends operant analysis to thinking, self-control, government, religion, and education. In November, a visit to his daughter Deborah's fourth-grade arithmetic class convinces him that classrooms violate everything known about reinforcement, and he builds his first teaching machine within days.^[12][13]

• 1957

  Two big books

  Schedules of Reinforcement, with Charles Ferster, catalogs thousands of hours of cumulative records. Verbal Behavior, developed from his 1947 William James Lectures, treats language as operant behavior.^[14][15]

• 1958–1959

  A journal, a chair, and a famous review

  The Journal of the Experimental Analysis of Behavior is founded. Skinner is named Edgar Pierce Professor of Psychology and receives the APA's Distinguished Scientific Contribution Award. In 1959 Noam Chomsky publishes his review of Verbal Behavior.^[16]

• 1968–1971

  National Medal of Science; Beyond Freedom and Dignity

  Receives the National Medal of Science in 1968. In 1971 Beyond Freedom and Dignity becomes a bestseller and puts him on the cover of Time, arguing that "autonomous man" is a fiction and that a culture must design its own contingencies.^[17]

• 1974

  About Behaviorism; retirement

  Retires from Harvard as professor emeritus and publishes his clearest statement of what radical behaviorism does and does not claim, written to correct twenty common misreadings.^[18]

• 1976–1983

  The autobiography

  Publishes a three-volume life — Particulars of My Life, The Shaping of a Behaviorist, and A Matter of Consequences — written in the same plain, external style he used for everything else.

• 1990

  Final address and death

  On August 10, at the APA convention in Boston, he accepts the first Citation for Outstanding Lifetime Contribution to Psychology and delivers a last talk, "Can Psychology Be a Science of Mind?" He dies of leukemia at home in Cambridge, Massachusetts, on August 18.^[19]

What is a Skinner box?

A Skinner box — Skinner's own term was operant conditioning chamber — is an enclosed, sound-attenuated space in which an animal can make a simple, repeatable response that the apparatus records and, under programmed conditions, rewards. Its purpose is not to trap the animal but to isolate one behavior and one consequence so that the relationship between them can be measured precisely, for hours at a time, without an experimenter in the room. A full tour of the box, part by part ›

How the operant conditioning chamber works

• The operandum. For rats, a small lever that closes a switch when pressed. For pigeons, a translucent plastic disk — the "key" — mounted at head height and lit from behind; a light peck closes a switch and registers a response.
• The food magazine. A dispenser that drops a 45-milligram pellet into a tray for rats, or raises a hopper of grain for a few seconds for pigeons. The sound of the magazine operating becomes a conditioned reinforcer, bridging the gap between the response and the food.
• Stimuli. Lights, tones, and the color of the key light let the experimenter signal when responding will pay off — the basis of stimulus control and the discriminative stimulus.
• Programming. Originally electromechanical relays and timers, later computers, deliver reinforcement on whatever schedule the experiment requires and record every response with its time.

The crucial feature is that the animal is free to respond at any time and at any rate. This free-operant method, as opposed to discrete trials in mazes and runways, is what made rate of response available as a measure — and rate turned out to be exquisitely sensitive to the conditions of reinforcement.^[6]

The cumulative recorder

Skinner's second invention was the instrument that made the data visible. A strip of paper moves at a constant speed under a pen; each response steps the pen a small fixed distance upward, and a diagonal tick marks each reinforcement. The result is a cumulative record whose slope is the rate of responding: steep means fast, flat means the animal has stopped, and the shape of the curve between reinforcers reveals the pattern a schedule produces. The famous "scallop" of the fixed-interval schedule and the "break-and-run" of the fixed-ratio schedule were first seen as pen strokes on this paper.^[14]

Why Skinner disliked the name

The nickname "Skinner box" came from Clark Hull's laboratory at Yale, not from Skinner, who never used it and objected to it — partly because it suggested a gadget rather than a method, and partly because the term became attached in the popular mind to something quite different, which is the next story.^[3]

The "baby in a box": the air crib and a persistent rumor

In 1944, before his second daughter Deborah was born, Skinner built what he called a baby tender and later an air crib: an enclosed crib with a large safety-glass front, a stretched canvas floor, and filtered, warmed air, so that the baby could sleep and play in a diaper alone, without blankets or layers of clothing, at a controlled temperature. It was a crib, used for sleeping and unattended play; Deborah was taken out to be fed, held, and played with like any other infant. Ladies' Home Journal published his article about it in October 1945 under a headline he did not choose, "Baby in a Box," and a number of families later used commercial versions.^[9]

Skinner's famous experiments

Four experiments come up again and again, partly because they are vivid and partly because each one makes a point that still matters.

"Superstition" in the pigeon (1948)

Skinner put hungry pigeons in a chamber in which the food hopper appeared for a few seconds at regular intervals — every fifteen seconds — no matter what the bird was doing. Six of eight birds developed a distinctive ritual: one turned counterclockwise around the cage between feedings, another thrust its head repeatedly into an upper corner, a third made a "tossing" motion as if lifting an invisible bar with its head, two swung their heads and bodies like a pendulum, and one made brushing movements toward the floor. Skinner's explanation was adventitious reinforcement: whatever the bird happened to be doing when food arrived was strengthened, which made it more likely to be under way at the next delivery, which strengthened it again. Contingency in the world is not required; contiguity is enough.^[11]

The experiment is also a lesson in how science corrects itself. When Staddon and Simmelhag repeated it in 1971 and recorded behavior throughout each interval, they found that the "terminal" behaviors just before food were much the same across birds — mostly pecking near the hopper — and looked less like accidentally reinforced rituals than like responses induced by the periodic arrival of food itself. The rituals were real; the explanation was more complicated than Skinner's.^[30] The glossary entry on superstitious behavior gives the everyday version.

Project Pigeon (1940–1944)

During the Second World War Skinner trained pigeons to guide a missile. A lens in the nose cone projected the image of the target onto a screen; the pigeon, harnessed inside, pecked at the image, and the position of its pecks steered the missile. Three pigeons voted for reliability. With support first from General Mills and then, in 1943, from the government's Office of Scientific Research and Development, the birds learned to track a target through distortion, noise, and cold, and kept pecking steadily under conditions that unsettled human observers. The project was cancelled in 1944 — the committee could not take a pigeon-guided bomb seriously against electronic guidance — and was briefly revived by the Navy after the war as Project ORCON.^[7] Its lasting product was accidental: in 1943, while teaching a pigeon to "bowl" a ball down a miniature alley, Skinner and his colleagues discovered how quickly behavior could be built by reinforcing successive approximations by hand — shaping.^[8]

The ping-pong pigeons

In a demonstration still shown in classrooms, two pigeons stand at either end of a small table and bat a ping-pong ball back and forth with their beaks. Each bird was first shaped to peck the ball, then to peck it toward the other end; once both could rally, food was delivered to the bird that got the ball past its opponent. Skinner presented it as a "synthetic social relation": competition assembled from individual contingencies, with no need to assume the birds understood the game.^[31] The companion demonstration in the same paper built cooperation the same way — two pigeons reinforced only when they pecked matching keys at nearly the same moment.

Teaching machines (1954–1958)

On a visit to his daughter Deborah's fourth-grade arithmetic class in November 1953, Skinner watched some children sit idle after finishing a problem sheet while others struggled, all of them waiting a day or more to learn whether their answers were right. By his own account he built a prototype teaching machine within days. The machine presented material in small steps, required the student to compose an answer rather than pick one, showed the correct answer immediately, and let each student move at his or her own pace. He described the principles at a 1954 conference and set out the case for "teaching machines" in Science in 1958, crediting Sidney Pressey's self-scoring devices of the 1920s as a precursor.^[13][22] The machines themselves went out of fashion within a decade; the principles — small steps, active responding, immediate feedback, self-pacing — reappear in programmed instruction and in most learning software written since.

Skinner's key contributions to psychology

What is radical behaviorism?

Radical behaviorism is Skinner's philosophy of the science of behavior. "Radical" means thoroughgoing, not extreme: where Watson's methodological behaviorism ruled private experience out of psychology because it could not be observed by a second person, Skinner ruled it in. Thinking, feeling, imagining, and seeing with your eyes closed are, in his account, behavior — covert, but subject to the same variables as any other behavior, and open to study through the verbal reports a community teaches each of us to make about them.^[10][18]

What radical behaviorism rejects is not the existence of mental life but its use as an explanation. To say a student studies "because she is motivated" or a rat presses "because it expects food" is, for Skinner, to stop the analysis one step too soon: the motivation and the expectation must themselves be explained, and when they are, the explanation turns out to be a history of consequences and a present set of conditions. He called inner causes that merely restate the behavior they are supposed to explain "explanatory fictions."^[12]

Three commitments follow:

• Behavior is a subject matter in its own right, not a symptom of something happening elsewhere (the mind, the brain). Neuroscience is welcome; it fills in mechanism, but it does not replace the functional relations.
• The causes of behavior lie in the organism's genetic endowment, its history of reinforcement, and its current environment. Feelings are real but are collateral products of those same contingencies — we feel the effects of the causes, not the causes themselves.
• Selection by consequences. Just as natural selection explains the appearance of design in organisms without a designer, reinforcement explains the appearance of purpose in behavior without purpose as a prior cause.^[23]

Controversies and critiques of Skinner

Chomsky's review of Verbal Behavior

The most consequential criticism Skinner ever received was Noam Chomsky's 1959 review of Verbal Behavior. Chomsky argued that terms like "stimulus," "response," and "reinforcement," precise in the pigeon laboratory, became vacuous metaphors when stretched over human language, and that children acquire grammar far too fast, from far too little input, for reinforcement to be the mechanism.^[16] The review is often credited with helping launch the cognitive revolution. Skinner never published a reply, and later said he had read only part of it. The detailed answer came from Kenneth MacCorquodale in 1970, who argued that Chomsky had reviewed Hull-style stimulus–response psychology rather than Skinner's book, had misdescribed reinforcement as a theory of drive reduction, and had criticized the book for failing to be a theory of grammar when it set out to be a functional analysis of why speakers say what they say.^[24] Both essays remain worth reading; on the specific question of syntax, most linguists sided with Chomsky, while Verbal Behavior's functional categories went on to become the basis of a large applied literature on teaching language to children with autism.

Free will and Beyond Freedom and Dignity

Skinner's 1971 book argued that the idea of an autonomous inner agent who freely chooses is a pre-scientific holdover, and that the real question is not whether behavior will be controlled — it always is — but by what and for whose benefit.^[17] The reaction was intense. Chomsky reviewed it, too, under the title "The Case Against B. F. Skinner," and philosophers objected that a science of behavior cannot settle a metaphysical question by fiat. Skinner's answer was that the traditional view had not produced a technology for solving problems like overpopulation, pollution, or war, and that dignity, properly understood, is the credit we give people when we cannot see what controls them.

Give me the specifications, and I'll give you the man!

— Frazier, the fictional founder of the community in Skinner's Walden Two, 1948

The ethics of behavioral control

Lines like Frazier's are why critics heard totalitarianism in Walden Two. Skinner's position was that a science of behavior is a tool, that the alternative to designed contingencies is accidental ones, and that the safeguard against abuse is countercontrol: the controlled must be able to control the controller. Whether that is enough is a live question, and it is why the ethics codes of applied behavior analysis put consent, least-restrictive procedures, and the client's own goals at the center. How ABA is practiced today ›

Skinner on punishment

Skinner was, throughout his career, an opponent of punishment as a method of control. His view rested on early evidence — his own 1938 experiments and W. K. Estes's 1944 dissertation — that punishment only temporarily suppressed responding while the reinforced behavior remained intact underneath, together with its side effects: fear, aggression, escape, and avoidance.^[6][25] Later work by Azrin and Holz showed that sufficiently immediate and intense punishment can produce lasting suppression, so Skinner's empirical claim was too strong.^[26] His practical conclusion — build behavior with reinforcement, and treat punishment as a last resort — is nonetheless where the applied field ended up.

Skinner's legacy

Few psychologists have left as many working descendants:

• Applied behavior analysis (ABA). A licensed profession in most U.S. states, built directly on Skinner's principles and his students' work, used in autism intervention, developmental disabilities, brain-injury rehabilitation, and behavioral medicine.
• Education. Programmed instruction, mastery learning, precision teaching, and school-wide Positive Behavioral Interventions and Supports (PBIS) all trace to his 1950s work on teaching. Operant conditioning in education ›
• Animal training. Shaping, conditioned reinforcers, and the clicker were carried from his laboratory into the training world by Keller and Marian Breland and later Karen Pryor. Reinforcement-based dog training ›
• Behavioral economics. The matching law, delay discounting, and the quantitative analysis of choice grew out of the operant laboratory, largely through his student Richard Herrnstein.
• Reinforcement learning in AI. The branch of machine learning behind game-playing programs, robotics, and the fine-tuning of large language models is a mathematical formalization of learning from consequences, and its founders cite the operant tradition explicitly.^[27]
• Self-management. Skinner's own late work on managing one's own behavior in old age, and the whole tradition of habit formation through antecedents and consequences, applies the three-term contingency to oneself.

His works are kept in print by the B. F. Skinner Foundation, led by his daughter Julie S. Vargas. The full history of operant conditioning, from Thorndike to reinforcement learning ›

Myths about B. F. Skinner

Selected bibliography

• The Behavior of Organisms: An Experimental Analysis (1938)
• Walden Two (1948)
• Science and Human Behavior (1953)
• Schedules of Reinforcement, with C. B. Ferster (1957)
• Verbal Behavior (1957)
• Cumulative Record (1959; expanded editions 1961, 1972) — collected papers
• The Technology of Teaching (1968)
• Contingencies of Reinforcement: A Theoretical Analysis (1969)
• Beyond Freedom and Dignity (1971)
• About Behaviorism (1974)
• Particulars of My Life (1976), The Shaping of a Behaviorist (1979), A Matter of Consequences (1983) — autobiography
• Enjoy Old Age: A Program of Self-Management, with M. E. Vaughan (1983)

None of Skinner's books is in the public domain, so none can be republished here. The books he built on — Thorndike, Morgan, James, Yerkes, Pfungst, Darwin — are, and they are in the library in full text.

Key takeaways

• Skinner's single ambition was a natural science of behavior: orderly relations between what an organism does and the conditions under which it does it, without appealing to a mind inside to do the explaining.
• The operant chamber and the cumulative recorder made rate of response the basic datum. Because the animal is free to respond at any time, rate became available as a measure, and it proved sensitive to the conditions of reinforcement.
• Radical behaviorism rules private experience in, not out: thinking and feeling are covert behavior, subject to the same variables as any other behavior. What it rejects is using mental states as explanations, which Skinner called explanatory fictions.
• Chomsky's 1959 review charged that laboratory terms become metaphors when stretched over language, and most linguists sided with him on syntax; Azrin and Holz showed that immediate, intense punishment can produce lasting suppression, so Skinner's empirical claim against punishment was too strong. His practical conclusion, build behavior with reinforcement and treat punishment as a last resort, is where the applied field ended up.
• The "baby in a box" was a climate-controlled crib, not an experiment. Skinner did not deny that thoughts and feelings exist, did not claim people are blank slates, and the "dozen healthy infants" line belongs to Watson.

Check yourself

A classmate says Skinner, like Watson, held that psychology should ignore thoughts and feelings because a second person cannot observe them. Is that right?

No. That is Watson's methodological behaviorism, which ruled private experience out. Skinner's radical behaviorism ruled it in: thinking and feeling are covert behavior, real and worth studying; what he rejected was treating them as the ultimate causes of what a person does.

In the 1948 experiment, pigeons were fed every fifteen seconds no matter what they did, yet six of eight developed rituals. A student concludes the birds had figured out that the ritual caused the food. What was Skinner's explanation, and what did later work add?

Skinner's explanation was adventitious reinforcement: whatever the bird happened to be doing when food arrived was strengthened, making it more likely to be under way at the next delivery. No understanding is required; contiguity is enough. Staddon and Simmelhag later found that the behaviors just before food were much the same across birds and looked induced by the periodic arrival of food itself, so the rituals were real but the explanation was more complicated.

Skinner argued for fifty years that punishment only temporarily suppresses behavior. Did the evidence support that claim?

Only partly. His view rested on his own 1938 experiments and Estes's 1944 dissertation, but Azrin and Holz later showed that sufficiently immediate and intense punishment can produce lasting suppression, so the empirical claim was too strong. His practical conclusion still stands in applied work: build behavior with reinforcement and treat punishment as a last resort.

Why did Skinner treat the free-operant method as a breakthrough rather than just a new gadget?

In mazes and runways the experimenter runs discrete trials. In the chamber the animal is free to respond at any time and at any rate, which made rate of response available as a measure, and rate turned out to be exquisitely sensitive to the conditions of reinforcement. The cumulative recorder then made that rate visible as the slope of a line.

Explain it to a friend. Explain the difference between Watson's behaviorism and Skinner's radical behaviorism in two sentences a twelve-year-old would follow.