reflexes, automatically elicited by the appropriate stimuli. Such stimuli are selected as US and responses elicited by them as UR. Thus Pavlovian conditioning, in which US elicits responses, is often called respondent conditioning. In instrumental conditioning, responses are under the control of the organism and are voluntary responses or ‘operants’.
Thus, in the two forms of conditioning different types of responses are conditioned. . In classical conditioning the CS and US are well-defined, but in operant conditioning CS is not defined. It can be inferred but is not directly known.