ABSTRACT
The scientific study of conditioning dates back to the beginning of the twentieth century, to the experiments of Ivan Pavlov in Russia and Edward Thorndike in the United States, working in quite different traditions and in total ignorance of one another. Pavlov developed the general procedures for studying classical conditioning, invented a terminology to describe it that is in use, and advanced an account of what was happening in his experiments, many elements of which are widely accepted. According to Thorndike the principle of instrumental conditioning is the law of effect. A response that produces one class of consequence will increase in probability; one that produces another class will decrease in probability. Instrumental responses are modified by their consequences, as opposed to Pavlovian conditional response, which are simply elicited by a stimulus regardless of their consequences.
