John B. Watson argued that psychology should be a strictly objective, experimental science focused on observable behavior, not introspection or reports of consciousness. This 1913 article helped define methodological behaviorism: studying behavior by relying on public, measurable events. It set a materialist-leaning research program by treating mental states as unnecessary for scientific explanation.
Watson and Rosalie Rayner reported conditioning fear responses in an infant later known as “Little Albert,” first published in 1920. The study became a famous (and now widely criticized) example used to support the idea that emotional reactions could be learned through classical conditioning. It also illustrated behaviorism’s push to explain complex human behavior using observable learning procedures.
Watson expanded his program beyond journal articles by publishing a widely read book on behaviorism in the mid-1920s. This helped move behaviorism from a research stance into a public-facing approach to psychology and human development. The book reinforced the idea that psychology should explain action in terms of environmental causes and learning history.
In 1937, B. F. Skinner argued that not all learned behavior fits the classical “stimulus-elicits-response” pattern. He distinguished respondent behavior (elicited by stimuli, like in Pavlov’s experiments) from operant behavior (emitted, then shaped by consequences). This distinction became central to Skinner’s methodological materialism: explain behavior through environmental relations and reinforcement history rather than hidden mental entities.
Skinner’s 1938 book presented an “experimental analysis” of behavior and formalized operant methods and concepts. It helped establish laboratory-based measurement of behavior (such as response rate) as a foundation for building general principles. The book marked a turning point from Watson’s broad program toward a detailed experimental framework for studying how consequences change behavior.
In 1943, Clark L. Hull published Principles of Behavior, offering a broad stimulus–response learning system built around reinforcement and “drive reduction” (reducing needs that motivate behavior). Hull’s work represented a more theory-heavy, model-building style within behaviorism that aimed to unify many findings into a single framework. Skinner’s later writings increasingly pushed back against this kind of explanatory “theory” when it relied on unobserved constructs.
In 1945, Skinner’s paper on the operational analysis of psychological terms addressed how psychologists use words like “idea,” “desire,” or “belief.” Rather than treating these as inner causes, he argued they should be understood by analyzing the conditions under which people learn to say them and the contexts in which they are reinforced. This move supported a methodological-materialist style in psychology: focus explanations on observable relations and functional context.
Skinner’s 1948 novel Walden Two presented a fictional community organized using behavioral principles, especially reinforcement and environmental design. While not a research report, it mattered historically because it showed how behaviorism could be framed as a practical technology for shaping behavior in everyday life. The book also made Skinner’s approach more visible—and more controversial—outside academic psychology.
In 1948, Skinner reported that pigeons could develop repetitive behaviors when food was delivered on a time schedule independent of what they did. He interpreted this as behavior strengthened by accidental timing between a response and reinforcement (sometimes called “adventitious reinforcement”). The paper became a widely cited example of how operant principles could explain seemingly irrational behavior without invoking hidden beliefs as causal explanations.
In 1950, Skinner argued that many learning theories explain behavior by appealing to events at another, unobserved level (for example, hypothetical internal processes). He pushed instead for explanations grounded in experimentally established relations between behavior and environment. This sharpened the divide between theory-driven stimulus–response systems and Skinner’s more strictly methodological, function-based approach.
Skinner’s 1953 book Science and Human Behavior extended operant principles from the lab to human topics such as language, self-control, and social organization. It aimed to show that complex human action could be analyzed using the same kinds of lawful relations studied in experiments. As a mid-century synthesis, it helped mark a “mature” phase of behaviorism that aligned with methodological materialism in its explanatory style.
In 1957, Skinner offered an operant analysis of language in Verbal Behavior, treating speech as behavior shaped by social consequences rather than as the expression of an inner language faculty. The book became a major landmark for behaviorism’s attempt to cover “higher” human abilities within a natural-science framework. It also helped define the end of this 1913–1950s arc, just as psychology increasingly turned toward cognitive explanations in the following years.
Behaviorism and Methodological Materialism in Psychology (John B. Watson to B.F. Skinner) (1913–1950s)