and Mrs. Vaughn are very busy people, but they recently took time away from their work schedule to talk with their psychologist about their...

Mr. and Mrs. Vaughn are very busy people, but they recently took time away from their work schedule to talk with their psychologist about their 9-year-old son Herb.  Here is there story.

“Herb used to be a very nice little boy.  He understood that his mother and I were very busy people, and he wanted something from us, he knew to ask quietly; we would help him get to it when we could.  By now when he wants something, he just yells at us.”

What would a behaviorist say has caused this situation, and what suggestions would he/she make for solving it?