In classical conditioning, when do critical events occur in relation to the response?

In classical conditioning, critical events—specifically, the pairing of the conditioned stimulus (CS) and the unconditioned stimulus (US)—occur before the response is elicited. This fundamental principle highlights that the conditioning process involves presenting the conditioned stimulus prior to the unconditioned stimulus in order to create an association between the two.

For instance, in Pavlov's experiments, he would ring a bell (the CS) before presenting food (the US) to dogs. As this pairing continues over time, the dogs learn to associate the sound of the bell with the arrival of food, leading them to salivate (the conditioned response) in anticipation of the food when they hear the bell. Therefore, the key aspect is that the conditioned stimulus must precede the response to establish that learned association, which underscores the critical importance of timing in classical conditioning.