Poor Norman Bates - he had no choice in life but to be a psychopath. Suffering horrific emotional abuse from the mother he adored, taught that sex was unclean and a sin. Preached to that all women are whores. A heady cocktail to produce a budding psycho. Enraged that his mother takes a lover showing blatant hypocrisy, he murders both the mother and lover and fakes a suicide note for his mother. When he ends up in a mental hospital, he develops dissociative identity disorder (multiple personality disorder) and part of him assumes the role of his mother due to guilt over murdering her. The mother side is what urges him to kill and act as the titular psycho. And he does this in splendiferous fashion. Knocking off poor Marion Crane in the shower and all of his subsequent murders. He has been shown through sequels to be a recidivist psycho. Treatment does not work and I am frankly perturbed that the authorities let him out of hospital considering he had killed so many people. But that's flipping sequels for ya!