Which of the following describes the primary function of a discriminative stimulus (SD)?

The primary function of a discriminative stimulus (SD) is to signal that reinforcement is available contingent upon a specific behavior. When the SD is present, it indicates to the individual that if they engage in a particular behavior, they will be more likely to receive reinforcement for that action. This concept is fundamental in understanding operant conditioning, as the presence of an SD increases the probability that the behavior will occur.

For instance, if a light turns on when a lever is pressed and food is dispensed when the lever is pressed while the light is on, the light acts as an SD, indicating to the organism that pressing the lever will result in food. This association helps establish clear behavioral patterns, as individuals learn to respond in the presence of the SD to obtain rewards.

The other options describe scenarios that do not accurately capture the role of an SD in behavior analysis. They either refer to situations where reinforcement is not available or where behavior is being inhibited rather than encouraged. Understanding the discriminative stimulus is crucial for effectively applying behavior analysis techniques in practice.