<P> Although operant and classical conditioning both involve behaviors controlled by environmental stimuli, they differ in nature . In operant conditioning, stimuli present when a behavior is rewarded or punished come to control that behavior . For example, a child may learn to open a box to get the candy inside, or learn to avoid touching a hot stove; in operant terms, the box and the stove are "discriminative stimuli". Operant conditioning involves voluntary behavior . However, in classical conditioning, stimuli that signal significant events produce reflexive behavior . For example, sight of candy may cause a child to salivate, or the sound of a door slam may signal an angry parent, causing a child to tremble . Salivation and trembling are not operants; they are not reinforced by their consequences . </P> <P> The study of animal learning in the 20th century was dominated by the analysis of these two sorts of learning, and they are still at the core of behavior analysis . </P> <P> Operant conditioning, sometimes called instrumental learning, was first extensively studied by Edward L. Thorndike (1874--1949), who observed the behavior of cats trying to escape from home - made puzzle boxes . A cat could escape from the box by a simple response such as pulling a cord or pushing a pole, but when first constrained, the cats took a long time to get out . With repeated trials ineffective responses occurred less frequently and successful responses occurred more frequently, so the cats escaped more and more quickly . Thorndike generalized this finding in his law of effect, which states that behaviors followed by satisfying consequences tend to be repeated and those that produce unpleasant consequences are less likely to be repeated . In short, some consequences strengthen behavior and some consequences weaken behavior . By plotting escape time against trial number Thorndike produced the first known animal learning curves through this procedure . </P> <P> Humans appear to learn many simple behaviors through the sort of process studied by Thorndike, now called operant conditioning . That is, responses are retained when they lead to a successful outcome and discarded when they do not, or when they produce aversive effects . This usually happens without being planned by any "teacher", but operant conditioning has been used by parents in teaching their children for thousands of years . </P>

Operant condition is an example of what type of learning