An unpleasant or noxious stimulus.

• A. Automatic Reinforcement
• B. Antecedent
• C. Abolishing operation
• D. Aversive Stimulus

Answer: (D)

An aversive stimulus is any event that an individual finds unpleasant or noxious. In ABA, such stimuli are often used as punishers when they are delivered contingent on a behavior, which tends to decrease the likelihood of that behavior in the future. Examples include loud noises, painful touch, extreme heat, or scolding.

The other terms describe different concepts: an antecedent is a stimulus that occurs before a behavior and can influence its likelihood; an abolishing operation is a motivational operation that reduces the value of a reinforcer and can increase the frequency of behavior that previously achieved that reinforcer; automatic reinforcement refers to reinforcement that occurs without social mediation.