Punishment involves a stimulus change that occurs contingent on the performance of a target behavior and causes a decrease in the future [Page 2772]probability of that target behavior. In positive punishment, the target response produces the addition of a stimulus, whereas in negative punishment, it produces the removal of a stimulus. It should be noted that the technical definition of punishment hinges on the effect of the stimulus on the target behavior: Punishment is in effect if, and only if, the behavior reduces in the future. This differs from lay usage of the word, wherein punishment is often equated with the presentation of any aversive stimulus or event, regardless of its effect on behavior.