Introduction to Learning and Behavior 4th Edition by Marcia Darvin Spada, Russell Powell, Lynne Honey,Diane Symbaluk

Exercise 3

Shahid usually salivates when he enters Joe's restaurant because he loves their turkey gumbo. One time, however, when the waiters were all dressed like clowns and bagpipes were playing in the background, he salivated much less. This appears to be an instance of ______ ______.