Punishment is any response to a behavior that "decreases" the likelihood of a behavior happening in the future. Punishment of a problem behavior should be used with reinforcement of the appropriate behavior. Appropriate behavior should always be reinforced even when using punishment for problem behavior. Just like reinforcement, punishment can be both positive and negative. Positive punishment is the "addition" of an stimulus that decreases the chances of future responses. This stimulus that is added is something aversive. Negative punishment is the "removal" of a stimulus that decreases the chance of future behaviors happening. The stimulus that is removed is something that the person likes.