Which statement accurately differentiates positive reinforcement from negative reinforcement?

• A. Positive reinforcement adds a pleasant stimulus; negative reinforcement removes an aversive stimulus; both increase the probability of the behavior
• B. Positive reinforcement removes an aversive stimulus; negative reinforcement adds an unpleasant stimulus; both increase the probability of the behavior
• C. Positive reinforcement adds an aversive stimulus; negative reinforcement adds a pleasant stimulus; both decrease the probability of the behavior
• D. Positive reinforcement removes a pleasant stimulus; negative reinforcement removes a pleasant stimulus; both have no effect

Answer: (A)

Reinforcement strengthens a behavior by changing what happens after it. Positive reinforcement adds something pleasant after the behavior, making it more likely to occur again. Negative reinforcement removes something aversive after the behavior, also making it more likely to occur again. The key is that both increase the likelihood of the behavior, differing only in what happens after the action—adding a good thing vs removing a bad thing. The other statements misstate what is added or removed, or describe effects that would reduce the behavior rather than increase it.