In classical conditioning, learning is most efficient when the unconditioned stimulus (UCS) is presented:

• A. immediately after the conditioned stimulus (CS)
• B. without any association to the conditioned stimulus (CS)
• C. at the same time as the conditioned stimulus (CS)
• D. long before the conditioned stimulus (CS)

Answer: (A)

Verified step by step guidance

1. Understand the basic concept of classical conditioning, where a neutral stimulus (which becomes the conditioned stimulus, CS) is paired with an unconditioned stimulus (UCS) that naturally elicits a response.
2. Recognize that for learning to be most efficient, the timing between the CS and UCS is crucial because the organism needs to associate the CS with the UCS effectively.
3. Recall that the UCS should be presented shortly after the CS to create a strong association; this timing is known as forward conditioning.
4. Note that presenting the UCS without any association to the CS or at the same time as the CS generally results in weaker or no conditioning.
5. Understand that presenting the UCS long before the CS is ineffective because the organism cannot predict the UCS based on the CS, which is essential for learning in classical conditioning.