In learning theory, discrimination is the ability to distinguish between a conditioned stimulus and other stimuli that do not signal the same outcome. The organism responds to the relevant cue and withholds the response from similar but irrelevant ones.

A dog conditioned to salivate to a specific tone will, early in training, also salivate to tones of nearby frequencies. With further training in which only the original tone is followed by food, the response becomes more selective. The same process occurs in operant conditioning: a pigeon pecks a key only when a particular light is on, because only then does pecking produce food. Discrimination training sharpens behavior and prevents wasteful responding.

Stimulus discrimination is the counterpart of generalization. Together they allow an organism to respond appropriately across a range of situations—broadly enough to catch similar opportunities, narrowly enough to avoid false alarms. In human learning the same principles apply to language categories, social cues, and skilled performance.

Discrimination turns a blunt association into a precise one.