Final answer:
In stimulus discrimination, the organism responds to either the SD or the SΔ during a procedure. It allows the organism to differentiate between relevant and irrelevant stimuli to respond appropriately.
Step-by-step explanation:
In the given scenario, the organism responds to either the SD (discriminative stimulus) or the SΔ (stimulus delta) during a stimulus discrimination procedure. Stimulus discrimination is the ability to respond differently to similar stimuli.
For example, if an organism has been conditioned to respond to a particular sound that predicts a rewarding event, it will only respond to that specific sound and not to other similar sounds that do not predict the same event. This allows the organism to differentiate between relevant and irrelevant stimuli in order to respond appropriately.