As a parent who has been through this process several times, a psychologist needs to have clear goals with both parents and child. My first goal for such an interview would be to gather information as to the problem, when the behavior or thinking first appeared, does it cause trouble in other places than home, and do the child and parents agree on what the exact problem is. The second goal would be to probe and find out if the child has seen anyone else for the issue, what was the treatment, and what were the results. The third goal would be what the child and parents want to see as a result of the interview or treatment options. The next goal would be to find out if there is any history in the extended family of this thinking or behavior. Lastly, I would think the psychologist would look at the health of the relationships in front of him or her to use in helping with a diagnosis and a plan for treatment.