Trivia: The security guard who gives "mother" a blanket at the end of the movie has the door opened for him by a young Ted Knight.
Trivia: The sound of the knife stabbing Marion's flesh in the shower scene was made by stabbing a melon.
Trivia: A body-double was used in the shower scene when anything else besides Janet Leigh's face, neck, shoulders, and arms are seen on screen.
Trivia: That freaky, shrill score of Psycho, created by Bernard Herrmann, inspired a well-known music producer to help create a popular song for a famous band. George Martin cites Bernard's score as an influence for 'Eleanor Rigby' by the greatest and most romantic band ever, the Beatles.
Trivia: Director Hitchcock hid the model of Mother in Janet Leigh's bedroom and listened to how loudly she screamed when she saw it to test its effectiveness.
Trivia: Walt Disney hated the film so much that he refused to allow Alfred Hitchcock to film at Disneyland for another film he directed.
Trivia: The CHP didn't use Fords in 1959 or 1960.
Answer: Norman and his mother lived together in the house on the hill above the motel. Norman's mother was such a demanding, controlling, overbearing woman that Norman was eventually driven to kill her. The enourmous guilt of this action, combined with the strain he was already under from her treatment of him, caused him to develop a sort of modified split personality: in addition to the existing Norman, he constantly heard his mother's voice in his mind and even had conversations with it. As time passed, the "Mother" voice in his brain began to have some occasional control over his body. Thus, sometimes Norman was in control, sometimes his mother was in control, and sometimes they could "speak" back and forth within his mind. Norman checked Marion into the hotel, but the sexual attraction caused by her presence made his disapproving Mother personality manifest and kill Marion. Having dealt with the situation, Mother retreated and Norman cleaned up, not remembering. At the end of the film, Mother blames Norman for the crimes because she is once again controlling his life and not wanting to take the blame herself. At the same time, this represents Mother forcing Norman down to some corner of his consciousness or even destroying it altogether, meaning that it is unlikely that Norman will ever manifest control again. This is why we hear Mother's voiceover and not Norman's at the end.
Phoenix