Answer:
a. differential reinforcement of incompatible behaviors
Step-by-step explanation:
Differential reinforcement of incompatible behaviors is an approach that involves replacing a problem behavior with a positive behavior by reinforcing and stimulating a positive behavior that cannot be exhibited the same time with the problem behavior. Differential reinforcement of incompatible behaviors works well especially in cases of people having autism spectrum disorder (ASD) where the individual engages in problem behaviors that inflict injury on the individual.
From the question above, the therapist uses the differential reinforcement of incompatible behaviors approach, as he uses praise as a reinforcement to increase the frequency at which Zander chews gum or sticks out his tongue, as these behaviors cannot occur together with the behavior of biting of lips. Chewing of gum, sticking out of tongues are reinforced in order to replace the biting of lips with them.