John Wilkes Booth was the son of prominent, wealthy actors. He, too, became an actor and was so popular, he was one of the first to have his clothes ripped off by fans. Hulton Archive/Getty hide caption
Psychology is the systematic investigation of the human mind, including behavior and cognition. It thus encompasses both normal and abnormal behavior. On the other hand, psychiatry is a branch of medicine dealing with mental illness.
In particular, psychologists assess whether the individual has the symptoms of any specific psychological diagnoses. An evaluation may also describe or explain the general psychological adjustment problems being presented by an individual, in an effort to understand the individual's behavior. Identifying specific problems is a necessary step in the development of a treatment plan.