I agree that you can never be 100% positive, that's why it's a behavioral hypothesis. You test the hypothesis by implementing the appropriate programming. It if works you have eliminated a lot of trying this or that. When it works you have a choice. What is your goal? Use the client as a science experiment or help the client and his parents. If you want to do science you can reverse the programming and see the client revert to pre-programming levels. Then you would have to re-program. You could be reasonably sure you were correct. If helping the client was the goal you would end by transfering treatment to the parents or other caretaker. So that the behavioral progress could be maintained. In the real world not many people would be paying you to do science. In this day of budget cuts and low reimbursement for psychological care reducing innappropiate behaviors is all that you are paid to do.