Final answer:
In classical conditioning, the neutral stimulus is presented before the unconditioned stimulus, leading to an unconditioned response. Through the acquisition phase, the neutral stimulus becomes a conditioned stimulus, eliciting a conditioned response.
Step-by-step explanation:
During classical conditioning training trials, the neutral stimulus (NS) is presented just before the unconditioned stimulus (UCS), which elicits the unconditioned response (UCR). In Pavlov's classic experiment, a tone (the NS) would sound before meat powder (the UCS) was presented, leading to the dogs salivating (the UCR). Over time, the tone itself, having been paired with the meat powder, would start to elicit salivation, making the tone a conditioned stimulus (CS) and the salivation in response to the tone a conditioned response (CR).
This process begins during the acquisition phase where the neutral stimulus and unconditioned stimulus become associated, and the neutral stimulus starts to trigger the conditioned response on its own.