Positive reinforcement strengthens a behavior by presenting a desirable stimulus after the behavior occurs. The consequence makes the behavior more likely in the future.

A child who receives praise for sharing is more likely to share again. A worker who earns a bonus for meeting a target is more likely to maintain high performance. In the laboratory, an animal presses a lever more frequently when lever-pressing produces food. The reinforcer may be tangible, social, or activity-based; what matters is that it is contingent on the response and that it increases the future probability of that response.

Positive reinforcement is most effective when it is delivered promptly and consistently during the acquisition of a new behavior, and when the reinforcer is genuinely valued by the individual. Over time, intermittent schedules can maintain the behavior with fewer reinforcers. The principle is central to education, parenting, clinical behavior therapy, and organizational management.

When a desirable consequence follows an action and that action then becomes more frequent, positive reinforcement has occurred.