Which of the following statements about classical conditioning is TRUE Group of answer choicesAcquisition of a CR is typically weaker when the pairings of the CS and US occur more frequentlyIn classical conditioning, the response initially elicited by the US is transferred to the CS such that the UR and CR are always the sameAcquisition of a CR is usually strongest when there is a relatively brief delay between the onset of the CS and the onset of the USClassical conditioning was discovered by Pavlov, who studied behaviour shaping in pigeonsIn classical conditioning, the presence or absence of the CR determines whether the subject is exposed to the US

The true statement about classical conditioning is: "Acquisition of a CR is usually strongest when there is a relatively brief delay between the onset of the CS and the onset of the US". This is because the closer in time the two stimuli are, the stronger the association between them will be. This is known as the contiguity principle.

Here's a step-by-step explanation:

1. Classical conditioning is a learning process in which an association is made between two stimuli.
2. The first stimulus is the conditioned stimulus (CS), which is initially neutral and does not elicit a particular response.
3. The second stimulus is the unconditioned stimulus (US), which naturally and automatically triggers a response.
4. When the CS is paired with the US over time, the organism learns to associate the two. This results in the CS triggering the same response as the US. This response is known as the conditioned response (CR).
5. The strength of the CR depends on the timing of the CS and US. If there is a brief delay between the onset of the CS and the onset of the US, the acquisition of the CR is usually strongest. This is because the organism can more easily make the association between the two stimuli.