You are a big fan of your grandmother’s chocolate chip cooki…

You are a big fan of your grandmother’s chocolate chip cookies. Just the smell of them causes you to feel hungry. One night she is making chocolate chip oatmeal almond cookies, a variation of her usual recipe. You smell the baking cookies and even though it is different than her usual cookie scent, you still suddenly feel hungry for a treat. This demonstrates the classical conditioning principle of ________.