But in Norman's case, he was simply doing everything possible to keep alive the illusion of his mother being alive.
10 seconds sound clip from the Psycho (1960) movie soundboard.
You can hear this line at 01:46:20 in the Blu-ray version of the movie.
Quote context
[...]
- Why was he dressed like that?
- That's what I meant when I said I got the story from the mother.
- You see, when the mind houses two personalities, there's always a conflict, a battle.
- In Norman's case, the battle is over, and the dominant personality has won.
[...]