B.F. Skinner came up with the theory that operant conditioning is a change or changes in behavior which are the result of an individual's response to events or stimuli that can occur in the environment. When a stimulus or response pattern is reinforced, the individual is conditioned to respond. Reinforcement is the key element in Skinner's stimulus-response theory. (Theory into Practice, p.2) A reinforcer is anything that strengthens the desired response. In the case of a teaching a third grade class, the reinforcer can be praising the students, which would be a positive reinforcer. Negative reinforcers can be punishing a student for acti