Yumi’s therapist is using Applied Behavior Analysis. He is t…

Yumi’s therapist is using Applied Behavior Analysis. He is trying to teach Yumi to brush her teeth on her own. The first few times, he rewards Yumi just for holding the toothbrush. Then Yumi gets a reward for moving the toothbrush around her teeth using only water to brush. Finally, Yumi is rewarded only if she uses toothpaste on her brush and brushes all of her teeth. Yumi’s therapist is using which of the following?