In operant conditioning, pioneered by B.F. Skinner (1904–1990), behavior is influenced less by the stimulus with which it is associated than by the effect of that behavior. Operant conditioning builds on Thorndike’s Law of Effect. If the effect of the behavior is positive, then it is reinforced, and the behavior is more likely to recur. If the effect of the behavior is negative, then it is punished and therefore less likely to be repeated.