Negative reinforcement strengthens a behavior by removing or avoiding an aversive stimulus after the behavior occurs. The behavior increases because it leads to escape or avoidance of something unpleasant.

Fastening a seat belt to stop the car’s warning chime is negative reinforcement; the behavior of buckling is strengthened by the termination of the annoying sound. Taking an aspirin to end a headache works the same way. In the laboratory, an animal learns to press a lever to turn off a shock. The key feature is that something undesirable is subtracted, and the response that produces the subtraction becomes more probable.

Negative reinforcement is often confused with punishment. Punishment decreases a behavior by adding an aversive consequence or removing a positive one. Negative reinforcement increases a behavior by removing an aversive condition. The distinction matters for understanding why certain habits persist and for designing effective behavior-change programs.

When an action reliably turns off something unpleasant, that action is being negatively reinforced.