Psychologists seek to understand human behavior and mental processes in sometimes complex circumstances. Most therapeutic approaches are linked fairly closely with the psychological perspective. In the history of treating mental illness, perspectives on treatment have been limited by the technology of the time. If one adopted a psychodynamic perspective, then one would employ a psychodynamic approach to treatment. Likewise, if one believed that abnormal behaviors were learned, then one adopted a behavioral approach to treatment. With serious illnesses, such as schizophrenia, multiple strategies from more than one of the perspectives may need to be employed. As an example, schizophrenia involves disturbances in thought processes, emotions, sensory and perceptual processes, and even motor movements. The biological perspective focuses on what biological factors might be playing a role in the situation. The psychodynamic perspective is primarily associated with the psychoanalytic method and theories originally developed by Sigmund Freud and expanded upon by his followers.