A tertiary reinforcer is defined as:

• A. A primary reinforcer like food.
• B. A natural stimulus that elicits a reflex.
• C. A punishment used to decrease behavior.
• D. A conditioned reinforcer that is reinforced by another conditioned reinforcer.

Answer: (D)

Understanding how reinforcers build on each other helps explain how dogs learn. A tertiary reinforcer, sometimes called a generalized reinforcer, is a reinforcer that gains value because it has been paired with other reinforcers. Its power comes from being reinforced by other conditioned or primary rewards, so it can support learning across different situations without needing direct access to a primary reward every time. In dog training, a token or praise sequence might serve as a tertiary reinforcer if the dog has learned that those cues lead to a variety of rewards later.

Thus, the best description is a conditioned reinforcer that is reinforced by another conditioned reinforcer. A primary reinforcer like food is inherently reinforcing and not learned. A natural stimulus that elicits a reflex is an unconditioned stimulus. A punishment decreases behavior, not reinforces it.