Final answer:
Statement 3 is the most correct about classical conditioning, explaining how extinction occurs when the CS is presented without the US. Statements about the US being a response and the necessity of multiple trials for learning a CS-US contingency are inaccurate.
Step-by-step explanation:
The subject of this question is classical conditioning as applied to psychology. More specifically, it delves into the mechanisms of learning through classical conditioning that involve a conditioned stimulus (CS) and an unconditioned stimulus (US) to bring about a conditioned response (CR). When looking at the statements provided by the student, the most correct statement about classical conditioning among them is statement 3: 'The CS must be presented multiple times without the US for extinction to occur.' This statement describes the process of extinction in classical conditioning, where the conditioned response diminishes and eventually disappears when the conditioned stimulus is repeatedly presented without being followed by the unconditioned stimulus.
It is important to note that the US is not a 'naturally occurring response' but rather a stimulus that elicits a natural response, thus statement 2 is incorrect. Additionally, while statement 1 suggests that learning the contingency between the CS and US always takes 'multiple trials,' acquisition can occur in a variable number of trials, dependent on the strength and timing of the stimuli. Statement 4 about discrimination is somewhat misleading as it focuses more on the absence of the CR when the CS doesn't predict it, rather than the process by which an organism learns to differentiate between similar stimuli. However, a better-formulated statement about discrimination would involve the organism responding to the CS but not to similar stimuli that do not predict the US.