Answer:
behavior therapist
Explanation: 
Behavior therapist - 
The type of therapist , who practices the method of behaviorism , to treat the patient , is referred to as behavior therapist. 
These therapist consider the specific behavior altering with some environmental factors. 
The treatment method of these therapist is not fixed , they have various method , which is used according to the demand of the patient . 
Hence, from the question, 
The correct term for the given information of the question is behavior therapist.