Answer:
CS, Placebo effect
Explanation:
The conditioned stimulus is a term that is used in classical conditioning by Pavlov. According to too the above statement, Habitual coffee drinkers conditioned with the smell, taste and the sight of coffee. It happened because they are classically conditioned by the stimulus. So that when they have provided a decaffeinated coffee in the form of placebo even after the habitual coffee drinker feels the same taste, smell, and sight of decaffeinated coffee.
This placebo coffee misses the active ingredients of the coffee particles. Habitual drinker feels the same arousal and the alertness because they are classically conditioned with coffee. In this procedure, the coffee plays a role of classically conditioned stimulus whereas the response is called a placebo effect.