Which of the following strengthens the likelihood of a behavior or response occurring?

A reinforcer is a stimulus or event that follows a behavior and increases the likelihood of that behavior occurring again in the future. This concept is grounded in operant conditioning, where behaviors are shaped by their consequences. When a behavior is reinforced, whether through positive reinforcement (adding a favorable stimulus) or negative reinforcement (removing an unfavorable stimulus), it strengthens the association between the behavior and its outcome, making it more likely that the behavior will be repeated.

In contrast, the other options do not serve to strengthen behavior. A response refers simply to the behavior itself without implying any consequence that would affect its frequency. Satiation occurs when a person has had enough of a particular reinforcer, which can actually decrease the likelihood of the behavior occurring. Punishment, on the other hand, is intended to decrease the likelihood of a behavior by introducing an aversive consequence or removing a positive stimulus after the behavior occurs. Therefore, a reinforcer is the most appropriate choice for strengthening behavior.