The friends are experiencing sensory-specific satiety. Sensory-specific satiety is a fullness based on declining satisfaction from eating one food or flavor. In this scenario, the friends ate large sandwiches. When presented with a new flavor of a different type, their hunger was renewed. The sandwiches were moist, most likely, and on thick, chewy bread; on the other hands, the chips were salty, crunchy, and thin.
