To strengthen the association between the conditioned stimulus and conditioned response, what should occur?

The strengthening of the association between a conditioned stimulus (CS) and a conditioned response (CR) primarily occurs through the proper timing of their presentation. For an effective association to be established in classical conditioning, the conditioned stimulus must occur shortly before the unconditioned stimulus (US). This temporal precedence allows the organism to learn that the CS is a predictor of the US, thereby reinforcing the bond between the two.

When the CS precedes the US, it establishes a predictive relationship. For instance, when a bell (CS) rings before food (US) is presented, the subject learns to associate the sound with the arrival of food. This sequence enhances the likelihood that the CR (salivation, in this case) will be elicited by the CS alone in the future.

Other options present methods of pairing the CS and US that do not effectively strengthen their association in the context of classical conditioning. Presenting the US first or having the CS follow the US can lead to confusion or a lack of clear association, as the organism may not connect the two stimuli in a meaningful way. Simultaneous presentation may create a degree of association, but it typically does not lead to as strong of a conditioned response as when the CS is presented beforehand, making it less