Give an example of a conditioned stimulus.

A conditioned stimulus is a previously neutral stimulus that, after becoming associated with an unconditioned stimulus, eventually comes to trigger a conditioned response. In classical conditioning, this process is known as conditioning or learning.

One of the most famous examples of a conditioned stimulus comes from the work of Ivan Pavlov, a Russian physiologist. In his experiments with dogs, Pavlov initially observed that the dogs would salivate (unconditioned response) when they tasted food (unconditioned stimulus). He then began to ring a bell (neutral stimulus) just before presenting the food. After several pairings of the bell with the food, the dogs started to salivate in response to the bell alone, even when no food was presented. In this case, the bell became a conditioned stimulus because it was able to elicit the salivation response (now a conditioned response) due to its association with the food.

Thus, the conditioned stimulus in Pavlov's experiment was the sound of the bell after it had been associated with the presentation of food.