Which of the following describes a conditioned response?

A conditioned response refers to a learned reaction that occurs in response to a previously neutral stimulus after it has been paired with an unconditioned stimulus. In classical conditioning, the unconditioned stimulus naturally elicits a response (known as the unconditioned response), while the neutral stimulus, after being associated multiple times with the unconditioned stimulus, generates a similar response—now termed the conditioned response.

For instance, if a dog hears a bell (the initially neutral stimulus) every time it is fed (the unconditioned stimulus), it will eventually begin to salivate (the conditioned response) at the sound of the bell alone, even without the food being presented. This illustrates how a neutral stimulus (the bell) can become conditioned due to its association with the unconditioned stimulus (the food).

The other options describe various aspects of psychological responses but do not capture the essence of what a conditioned response uniquely represents in the context of classical conditioning. A natural reaction to an unconditioned stimulus and a reflex that occurs without any learning pertain to innate responses, while a response that is always voluntary misinterprets the nature of conditioned responses, which can often be involuntary or automatic.