Carson used to enjoy lime sherbet, so when he was in mexico he tried frozen lime margaritas. after his fourth margarita, carson became extremely ill. now he finds that even the sight of lime sherbet in a bowl can make him feel queasy. in this example, the unconditioned stimulus is:

The unconditioned stimulus (UCS) here is foods and beverages that are lime flavored. An UCS is a stimulus that unconditionally and automatically elicits a response of some kind. In this example, the UCS (lime flavored food) automatically elicited a response (queasiness) in Carson. The term 'unconditioned stimulus' originates from Ivan Pavlov's theory of classical conditioning.