Final answer:
The key distinction between the CS and the SD is that the CS is a signal for a contingent relationship where a conditioned response is elicited, whereas the SD indicates that no reinforcement will follow in operant conditioning. Stimulus discrimination allows an organism to respond only to the CS and not other similar stimuli.
Step-by-step explanation:
The main distinction between the conditioned stimulus (CS) and the stimulus delta (SD) is that the CS cues when a contingent relationship is valid. The SD, meanwhile, signals that a certain response will not be reinforced in operant conditioning. In classical conditioning, the CS becomes associated with the unconditioned stimulus (UCS), eliciting a conditioned response (CR) after repeated pairings. An example of this is Pavlov's dogs salivating (CR) to the sound of a bell (CS) as it has been associated with the arrival of food (UCS).
In stimulus discrimination, an organism learns to respond only to the CS and not to other similar stimuli. This means that the organism demonstrates the CR only to the CS. For instance, a dog trained with an invisible fence will learn to associate the edge of the yard (CS) with receiving a small shock (UCS), hence feeling fear and staying within boundaries (CR). The dog will not feel fear when it is away from the edge of the yard, indicating stimulus discrimination.