I believe his mind’s interpretation of his mother is how he perceived her. Perhaps killing those who come into contact with her son, particularly women, was something she would do out of jealousy, and she would force Norman to dispose of the body. If this were the case, it would explain Norman’s calm composure in disposing of Marion Crane and cleaning the hotel room. I found the scene peculiar in that upon seeing the dead body and the blood on his hands, he was shocked but then calmly went about the job. He had clearly done it before.

I can believe that his mother took over sporadically throughout the film. There are scenes where Norman’s demeanor becomes somewhat sinister, like after Marion leaves his company and sees she lied about her name. There was also something disturbingly cocky about the way he ate candy corn. He looked like someone who knew he had done something terrible and had complete confidence that he was going to get away with it. These moments, I believe, were of her in charge. I could see when he was himself when being questioned about Marion. He was the same timid man he was when we first met him. If I’m correct, it almost seems as if his mother abandoned Norman in the fallout of the initial crime, but she shows back up again when she thinks they got away with it. If I was right about her having killed and forcing Norman to clean up after her, perhaps this is the situation playing out in Norman’s mind.

Alternatively, there is one other way I can view Norman’s psychopathy, and that’s as Norman as the killer and his mother as an innocent bystander. The psychiatrist said that Norman’s mother had become the dominant personality in control and stated that she was the perpetrator of Norman’s horrible crimes. Contrary to this, we hear the mother explain that it was her son who was the perpetrator. Because it is unclear which personality Norman falls under at various points, she could be telling the truth, and the doctor was wrong in his assessment. Perhaps the only thing he did get right was that there had always been something wrong with Norman, even before the death of his mother. Norman’s explanation to Marion about what his mother had become could be a way of shifting the blame to her because he’s convinced himself that it’s true, that she was the one doing the killing.

The doctor describes the beginnings of the other personality as Norman having been pretending she was real, but he eventually started to believe it. If her treatment of him were an extension of her emotional dependency on him, she would have known that if he hurt someone, he would have been taken away. It’s hinted that Norman had spent time in an institution when he describes the treatment of a facility in which Marion suggests he put his mother. I would bet that he was in this place after his sociopathic urges got the better of him until his mother got him out. It could be that in life, she kept his more violent tendencies at bay in her emotionally abusive ways until Norman eventually let them loose on her and her lover. He still needed the normalcy she provided just as Ed Gein had, but because she wasn’t there, he made himself believe she was responsible for his crimes and blamed her for the things he did. This wouldn’t be hard with her as a separate ego within his mind. If he somehow made her real, he could make himself believe she was the murderer and allow him to retain normalcy. But, when she takes control, she also holds the truth, that it’s still him who’s the real killer, but she is still the abuser she had been in life. Of course, this is just an audience members theory. I like to believe that Alfred Hitchcock left a lot to the imagination when he made Psycho in the 1960s.