Classical and Operant Conditioning

Classical conditioning — learning by association

Pavlov paired a bell with food. Food is the unconditioned stimulus (US) producing salivation, the unconditioned response (UR). After pairing, the bell alone — now the conditioned stimulus (CS) — produces salivation, the conditioned response (CR).

Extinction follows if the CS appears repeatedly without the US. Generalisation means similar stimuli also trigger the CR; discrimination means only the exact CS does.

Watson's Little Albert study conditioned a child to fear a white rat, and the fear generalised to other furry objects.

Operant conditioning — learning from consequences

Skinner showed behaviour is shaped by what follows it. Reinforcement increases behaviour; punishment decreases it. Positive means something is added; negative means something is removed.

Schedules of reinforcement

• Fixed ratio — after a set number of responses. High rate, brief pauses after reward.
• Variable ratio — after an unpredictable number. Highest rate, most resistant to extinction — this is how slot machines work.
• Fixed interval — first response after a set time. Rate rises just before the deadline.
• Variable interval — unpredictable time. Steady, moderate rate.