AP Psychology Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

In classical conditioning, a conditioned stimulus (CS) is an originally neutral stimulus that, after being paired with an unconditioned stimulus (US) that naturally elicits a response, eventually triggers a conditioned response (CR) on its own. The process involves the association of the neutral stimulus with the unconditioned stimulus, which leads to learning and the subsequent elicitation of a response without the presence of the unconditioned stimulus.

For instance, if a bell (the neutral stimulus) is rung just before presenting food (the unconditioned stimulus) to a dog, the dog will eventually begin to salivate (the conditioned response) at the sound of the bell alone, even in the absence of food. This transformation of the bell from a neutral stimulus to a conditioned stimulus illustrates how learning occurs through association in classical conditioning.

The other options do not accurately describe the role of a conditioned stimulus. A stimulus that naturally causes a response refers to an unconditioned stimulus, while a learned response pertains to conditioned responses rather than stimuli. Lastly, a stimulus that elicits a neutral response does not contribute to the conditioning process.