- Law of Effect
- Thorndike's foundational principle (1898): responses followed by a satisfying state of affairs are strengthened — the stimulus-response bond is 'stamped in' — while responses followed by an annoying or neutral state of affairs are weakened and 'stamped out'. Originally derived from animal experiments with puzzle boxes, the Law of Effect established that the consequences of behaviour feed back to alter the probability of that behaviour recurring. It was the direct conceptual precursor to Skinner's operant conditioning.
- Reinforcement
- Any consequence that increases the future probability of the behaviour it follows. Positive reinforcement adds a desirable stimulus after a response (e.g., praise following correct recall). Negative reinforcement removes an aversive stimulus after a response (e.g., relief of discomfort following avoidance behaviour). Both increase responding — negative reinforcement is frequently confused with punishment, but they are opposite in effect: punishment decreases responding, reinforcement increases it.
- Reward prediction error
- The discrepancy between the reward an organism expects and the reward it actually receives. The Rescorla-Wagner model (1972) formalised this as the primary driver of learning: the change in associative strength (ΔV) on any trial is proportional to the difference between what was obtained (λ) and what was predicted (V). When reward exceeds prediction, the association strengthens; when reward falls short of prediction, it weakens; when reward exactly matches prediction, no learning occurs. The model correctly predicted blocking — the finding that a fully predicted outcome cannot be used to condition a new stimulus.
- Delay discounting
- The psychological devaluation of rewards as a function of their temporal distance from the present moment. Psychologically, discounting is hyperbolic rather than exponential: the subjective value of a reward drops steeply for short delays and more gradually for longer ones, creating preference reversals. A person may prefer £100 now over £110 next week, yet prefer £110 in 53 weeks over £100 in 52 weeks — a logically inconsistent pattern explained by hyperbolic discounting. This feature of reward psychology has direct implications for understanding impulsive choice, addiction, and self-control failure.
- Partial reinforcement extinction effect (PREE)
- The counterintuitive finding that behaviours reinforced on partial schedules are more resistant to extinction than behaviours reinforced on every trial. Jenkins and Stanley (1950) established this as one of the most robust phenomena in learning psychology. The explanation most consistently supported is the discrimination hypothesis: under continuous reinforcement, the organism quickly discriminates the extinction condition (no reward) from training; under partial reinforcement, non-reward during training is indistinguishable from extinction, so the organism persists far longer before extinguishing.
- Secondary reinforcement
- A stimulus that acquires reinforcing properties not through its intrinsic biological value but through repeated pairing with a primary reinforcer (food, water, warmth, pain relief). Money is the most pervasive secondary reinforcer in human behaviour — valuable only because of its consistent association with primary rewards. In clinical psychology, token economy programmes exploit secondary reinforcement by awarding tokens for target behaviours; the tokens can later be exchanged for primary or otherwise valued reinforcers, allowing contingencies to be applied in settings where direct primary reinforcement is impractical.