Which term describes a stimulus that signals reinforcement is available when the behavior occurs?

• A. A CS
• B. A US
• C. An SD
• D. An MO

Answer: (C)

Discriminative stimulus is a cue that signals reinforcement is available for a particular behavior. When this cue is present, performing the behavior leads to reinforcement; without it, reinforcement is not guaranteed. This creates discrimination or stimulus control—the behavior is more likely to occur in the SD’s presence because the reinforcement contingency is active there. This differs from a conditioned stimulus, which signals that a reflexive or conditioned response is coming (a US follows), rather than signaling reinforcement for an operant behavior. A motivating operation changes how valuable the reinforcement is at the moment, making the behavior more or less likely, but it doesn’t indicate that reinforcement is currently available.