‘PSYCHO’ ANALYSIS

Why’s that chilling shower scene so memorable? New doc breaks it down clinically

HOW many times has documentarian Alexandre O. Philippe watched Alfred Hitchcock’s shrieky-strings “Psycho” shower scene?

“Thousands of times is probably not an overstatement,” he tells The Post. “But the scene is a Pandora’s box. I feel like I’m just now scratching the surface.”

When “Psycho” premiered in 1960, viewers had no idea what was coming. They assumed Janet Leigh, a movie star, would be the heroine. Less than halfway through, she’s brutally murdered. “Hitchcock is removing his protagonist 40 minutes into the film, which at the time was completely novel,” Philippe says. “I think most people were thinking, ‘There’s a trick here.’ And then he lingers. He lets it sink in. This is a different kind of cinema; this is not what people signed up for.”

Opening Friday, Philippe’s film “78/52: Hitchcock’s Shower Scene,” which refers to the number of setups and edits in the deeply unsettling scene, unpacks its legacy: “It had a profound effect on cinema and on culture,” he says, “but it’s also very problematic. It was the first time murder became an acceptable part of entertainment. And when you add that it’s a woman, vulnerable, naked, alone in a shower — and the sort of cinema that [it] spawned — we can still ask: Was it good that it happened, or not?”

Here, Philippe looks at several formative shots from the scene that is to showering what “Jaws” is to swimming in the ocean.