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.
Psychological assessments are different from other assessments, such as educational testing completed by Special Education & Resource Teacher in a school, or an assessment completed by a Psychiatrist in a crisis clinic, or an assessment for services by an intake worker at a therapy clinic, or a Social Worker at a Family Health Team.