A reinforcer is any consequence or stimulus that, when presented after a behavior, increases or maintains the likelihood of that behavior occurring again in the future. Reinforcers can be positive (adding a pleasant stimulusStimulus is defined as any change in the environment or form of energy that affects an organism’s behavior or physiological state. Stimuli can be external or internal, and they can elic... More) or negative (removing an aversive stimulus).
Example
A student completes their homework, and as a result, the teacher gives them extra playtime during recess. The extra playtime serves as a reinforcer because it increases the likelihood that the student will continue completing their homework in the future.