1. a procedure in which an operant response is reinforced in the presence of a particular stimulus but not in the absence of that stimulus. For example, a rat’s lever-press response might be reinforced when a stimulus light is on but not when the light is off. The rat will eventually learn to press the lever only when the light is on. See discrimination of cues. 2. in sport, the training of the ability to identify task-relevant cues and their meaning.