conditions" and the school announced that it would resume the use of electrical shocks. Concepts Behavior Behavior refers to the movement of some part of an organism that changes some aspect of the environment. Often, the term behavior refers to a class of responses that share physical dimensions or functions, and in that case a response is a single instance of that behavior. If a group of responses have the same function, this group may be called a response class. Repertoire refers to the various responses available to an individual; the term may refer to responses that are relevant to a particular situation, or it may refer to everything a person can do. Operant conditioning Operant behavior is the so-called "voluntary" behavior that is sensitive to, or controlled by its consequences. Specifically, operant conditioning refers to the three-term contingency that uses stimulus control, in particular an antecedent contingency called the discriminative stimulus (SD) that influences the strengthening or weakening of behavior through such consequences as reinforcement or punishment. The term is used quite generally, from reaching for a candy bar, to turning up the heat to escape an aversive chill, to studying for an exam to get good grades. Respondent (classical) conditioning Respondent (classical) conditioning is based on innate stimulus-response relationships called reflexes. In his famous experiments with dogs, Pavlov usually used the salivary reflex, namely salivation (unconditioned response) following the taste of food (unconditioned stimulus). Pairing a neutral stimulus, for example a bell (conditioned stimulus) with food caused the dog to elicit salivation (conditioned response). Thus, in classical conditioning, the conditioned stimulus becomes a signal for a biologically significant consequence. Note that in respondent conditioning, unlike operant conditioning, the response does not produce a reinforcer or punisher (e.g. the dog does not get food because it salivates). Reinforcement Reinforcement is the key element in operant conditioning and in most behavior change programs. It is the process by which behavior is strengthened. If a behavior is followed closely in time by a stimulus and this results in an increase in the future frequency of that behavior, then the stimulus is a positive reinforcer. If the removal of an event serves as a reinforcer, this is termed negative reinforcement. There are multiple schedules of reinforcement that affect the future probability of behavior. "[H]e would get Beth to comply by hugging him and giving her food as a reward" Punishment Punishment is