In classical conditioning, the organism learns the relationship between one stimulus (bell) and the other (food). The CS and the UCS are connected together so that the animal learns to respond to the CS just as it does to the UCS. The bell by being paired consistently with food acquires the potentiality of evoking the same response (i.e., salivation) as was evoked by the food. Pavlov termed classical conditioning as Stimulus-Substitution. But in operant conditioning, the organism learns the relationship between a response (i.e., lever pressing) and a stimulus (i.e., food). While classical conditioning is S-S type of learning, the operant conditioning is S-R type learning.
The UCS (i.e., food) elicits the natural and biological response of salivation (UCR). In operant conditioning, the response has to be spontaneously emitted by the organism. Among several responses emitted, one response is followed by reinforcement. The probability for the occurrence of that response increases, and the probabilities for other responses decrease. Since the response to be given in operant conditioning is to be shown by the organism, the response is under the voluntary control of the organism. In classical conditioning, the UCS evokes a natural response; so the nature of the response is involuntary. Since involuntary responses (i.e., blood pressure, pulse rate) can be brought under voluntary control, they can also be instrumentally conditioned. Biofeedback is a method of bringing involuntary responses under voluntary control.
In classical conditioning, the UCR (salivation to food) and the CR (salivation to bell) show a great deal of similarity. But in operant conditioning, the CR and the UCR are usually different, and sometimes, radically dissimilar. All the movements of the rat inside the Skinner Box (e.g., jumping, scratching, crawling etc.) in the first trial before it has received food constitute the UCR. The CR is the response of lever pressing, which is very different from the UCR.
In classical conditioning, the response comes after the reinforcement. The reinforcement is powerful to elicit a natural biological response. The arrangement in operant conditioning is such that the reinforcement is given only after the correct response is made. While in classical conditioning response follows the reinforcement, in the operant procedure, reinforcement follows the response.
The CS, in classical conditioning is a specific identifiable stimulus like the bell or the light. In the operant conditioning, the array of stimulus cues present in the box serves as the CS. The sight of all the parts of the Skinner box, and the smell form a stimulus field where the organism's response takes place. All these serve as the CS in the instrumental procedure.
In the classical procedure, the type of reinforcers given determines the organism's response. It has less freedom for action. Thus, the organism plays a passive role, while in operant conditioning, the organism plays an active role, it has more choices for operating on its environment, and its actions determine whether or not it will receive reinforcement.
The classical conditioning is governed by the principle of contiguity, which means that the response and the stimulus must be very close in time. When the bell (CS) is sounded, the response of salivation (UCR) elicited by food (UCS) must occur within a very short time. If the time gap is more, the conditioning will not take place. The important law for the operant/instrumental conditioning is the Law of Effect. Whether or not a response would be learned depends upon the effect of the response. If the response brings reinforcement, it will be learned; if it does not, it will not be learned.
Reinforcement can be continuous or partial. How do the two procedures respond to partial reinforcement, that is when reinforcement is not given on all occasions? In classical conditioning, partial reinforcement (i.e., food is given on some trials and not given on others) reduces the rate of learning. The organism takes more trials to learn the response. The extinction of a response learned under partial reinforcement is slightly delayed. The Partial Reinforcement Effect (PRE) is different for operant conditioning. The rate of response is higher in operant conditioning under conditions of partial reinforcement. If the response is learned under partial reinforcement schedules, it takes longer to be extinguished, because organism fails to discriminate between the acquisition phase and the extinction phase. In the operant/instrumental procedure, the partial reinforcement results in greater resistance to extinction.
In Summary, the operational distinctions between the classical and the operant conditioning techniques make a reader sensitive to the subtle differences existing between the two techniques, even if it is difficult to discriminate between the presence of light and other stimulus conditions. As a consequence, it responds when the light is on, and does not respond when light is absent and other stimuli are present. This is discrimination learning. The light signal serves as a stimulus to control the behavior of the rat. In other words, rat's behavior comes under the stimulus control of light. Teenagers show disciplined behaviors in the presence of their parents. Students study hard, when the teacher is present. Parents and teachers are discriminative stimuli. The behaviors of the teenagers and students have come under the stimulus control of their parents and teachers respectively. Discrimination learning accounts for great many life experiences representing complex human behavior.