A Door Slowly Opens....
Being pretty much the first of its kind(as a slasher movie, not as a horror Gothic), Psycho felt like it didn't even KNOW what the "slasher movie clichés" needed to be. We don't have Mrs. Bates chasing people all around the Bates house, or "getting killed but coming back to life." We don't have a "POV handheld camera shot" from Mrs. Bates view as she comes at her victims.
And we don't have doorknobs slowly turning.
But we DO have doors slowly opening.
It is here worth noting that both of the two shock murder scenes in Psycho rely on a door slowly opening as the "frisson"-producing gut check that signals imminent horrible death and terror.
The shower scene opens with various cuts from various angles on Janet Leigh taking a cleansing, erotic shower. And then we get one big medium shot(almost an "interior long shot") from an impossible position: we are "in the shower wall" looking out past Janet showering and noticing that there is a wide swath of "open space" behind and to the left of her. The space between the shower and the closed bathroom door.
And then that bathroom door slowly opens and though things are blurry though the plastic shower curtain, we can see a figure invading Miss Leigh's private space, creeping up -- eventually pulling that shower curtain open. Scream time.
But there is something to be said for how that bathroom door suddenly just "falls into the shot". I saw the shower scene with an audience in the 70's through the 00's, and you could hear a collective groan as the door opened through the blurry curtain and ANOTHER HUMAN BEING entered through it. I can only imagine how crazy a 1960 "new" audience would be for the effect.
Later in the film, a slowly opening door is the first of two uses of the door for the second murder, of Arbogast on the stairs. As he climbs, there is the high angle close-up of the Mother's door slowly opening -- a classic of precision as light spills onto the patterned carpet and ONLY when the door has opened enough so that there is no more room for light on the floor -- does Hitchcock cut to a final shot of Arbogast almost reaching the landing before leaping to the "money shot" from high above, of Mother rushing out from that open door(does not the door open even FURTHER to allow Mother to make her mad dash? I'll have to look.)
It would seem that these "slowly opening door" shots have several roles to play. One, circa 1960, is to forewarn the audience ahead of time that shock is about to occur. The audience members are given time to cover their eyes if they wish to.
When Psycho went out as a catalog rental film starting in the 70's, it came with a disclaimer: PSYCHO is not to be shown to the elderly, pregnant women, children, or people with heart problems." Those were the days. I would expect that Hitchcock and his studio backers and the censors felt that if the shower curtain opened WITHOUT the shot of the door opening, or if mother ran out of her room at Arbogast WITHOUT the shot of the door opening...heart attacks might ensue. Word.
If the "door slowly opens" shot had a practical application(i.e. to prevent heart attacks) it most certainly had a dramatic(or more to the point, MELOdramatic) application as well. New York Times critic Bosley Crowther rather called it : "That's the way it is with Hitchcock's picture: slow build-ups to sudden shocks until a couple of people have been gruesomely punctured..."(hey, man - spoilers.) I believe that Crowther also spoke to the "old-fashioned melodramatics" of Psycho.
Hitchcock would have likely agreed. Hitch always seemed a little bit perturbed at the success of Psycho because its shocks were perhaps too easily attained. "This is my Boogie Man is Coming to Get You Movie" Hitchcock once said. The doors slowly opening shots came dangerous close to what Hitchcock said he wanted to do: avoid the cliché. But they were very artful shots -- cinematic, masterly, profound.
And this: by linking Mother(in her monstrous murderer mode) to those slowly opening doors, they invested a mere old woman(or actually, a mere young man) with a certain sinister, inhuman scariness. The door slowly opens -- bloody death comes in .
The doors were totally necessary. Mother could have entered the bathroom through an open doorway, or run out at Arbogast through an open doorway (already open.) But there was much more portent and decidedly more "flavor" to opening the doors slowly.
And that's another part of how Psycho works beyond the surface.