Definition
Behaviorism is the school of psychology, founded by John B. Watson in 1913 and extended most influentially by B. F. Skinner, that defines the proper subject matter of psychology as observable behaviour and its environmental causes — not consciousness, introspection, or inner experience. The slogan: psychology should be a natural science, modelled on physics, dealing only in stimuli and responses that can be measured by an independent observer.
The school produced two principal frameworks. Classical conditioning, drawn from Ivan Pavlov's work on salivating dogs, describes how a previously neutral stimulus comes to elicit a reflexive response through repeated pairing with an unconditioned trigger. Operant conditioning, developed by Skinner, describes how the consequences of a voluntary behaviour — reinforcement or punishment — shape its future frequency.
Why it matters
How it works
Classical conditioning works by pairing: a bell sounds before food appears, and after enough pairings the bell alone makes the dog salivate. The mechanism is associative — the brain links two stimuli that reliably co-occur. Therapies built on this principle include systematic desensitisation for phobias, in which a feared stimulus is paired with relaxation until the fear response weakens.
Operant conditioning works by consequences. Reinforcement — anything that increases the probability of a behaviour — can be positive (adding something rewarding) or negative (removing something aversive). Punishment, conversely, reduces probability. Skinner showed that schedules of reinforcement — continuous, fixed-ratio, variable-ratio — produce very different patterns of behaviour, with variable-ratio schedules producing the most persistent responding. This finding underwrites the design of slot machines, video game progression systems, and many social media notification patterns.