There is so much about this film that the casual viewer misses, too! I'm a huge Hitch fan.
The character of Norman was based, of course, on Ed Gein (think there may be a thread about him in the Serial Killers section...)
Very few people today realise just how this movie made possible the type of movies we see today... Censorship had been pretty tight up until this film came along. It was the first to depict sexuality and violence in a graphic manner and although the "youth" market was ready for such a change, the older audience resisted it. For this reason, "Psycho" was initially received by many with anger and critical rejection; funny how it is now considered Hitch's greatest film by most (me? I like "The Rear Window"...)
"Psycho" also included the very first love scene in American popular cinema ever to feature a pair of lovers lying half-naked on a bed

And not only did Psycho depict two brutal murders, but the first occurred in the "intimacy" of the shower. As a result, Hitch had to fight to make the film as close to his vision as possible and find ways to work around censorship laws. When the censors demanded he re-edit the shower scene on account of a fleeting glimpse of Janet Leigh's breast

, Hitch simply sent back the
original cut on the (correct) assumption that they either would not re-screen it or would fail to see the barely noticeable nudity the second time around! As well, Hitch reportedly shot the film in black and white only because he knew the censors would never approve the very bloody shower scene in color. As he put it: "Our big problem...is trying to make the censors understand that the young people are much more sophisticated than they used to be".
Hitch used ink to create the "blood" spiralling down the drain in the shower scene, incidentally.
The complete Psycho screenplayEd Gein thread in Serial Killers~ Viper ~