Eight-year-old Randy has behavioral difficulty in school and is overly aggressive with the other children. His parents seem to ignore his problems and blame the school and the other children. His parents are convinced that Randy has attention-deficit/hyperactivity disorder. When they take him to a child psychiatrist, the psychiatrist is reluctant to give the diagnosis after observing the unhealthy interactions between the family members and between the parents. The psychiatrist's reluctance to give this diagnosis is based on the _____ related to the cause and diagnosis.