An unconditioned stimulus is defined as

• A. A stimulus that has to be learned through pairing
• B. A neutral cue that becomes meaningful after conditioning
• C. An innate stimulus that elicits a natural, unconditioned response
• D. A punisher that decreases a behavior

Answer: (C)

In classical conditioning, the unconditioned stimulus is something that naturally triggers a reflexive response without any learning. It’s innate, not learned through experience. For example, presenting food to a hungry animal causes salivation automatically—the salivation is the unconditioned response. Because this happens without prior conditioning, the stimulus that elicits it is defined as unconditioned.

This differs from a neutral cue that becomes meaningful after conditioning, which is a conditioned stimulus, and from punishment in operant conditioning, which decreases a behavior.