Morris was then a graduate student at U.C. Berkley, but the extensive interviews he did with Gein (he believes the only ever done) helped set Morris on the path that would be his life’s work — films that might in some way be summarized by a scene in ‘‘Psycho’’ that deeply affected Morris. Near the end of the film, a psychiatrist offers a pat, insufficient explanation of Gein’s psychosis, which Pauline Kael called ‘‘arguably Hitchcock’s worst scene.’’

‘‘You feel that all psychological explanation is defeated,’’ says Morris. ‘‘It’s the ultimate noir idea, that somehow psychological explanation isn’t enough. It’s defeated by some kind of mechanism that stands behind all of our plans and our thoughts, our machinations. It’s the feeling of being haunted by the inexplicable and the unknown.’’

In ‘‘Hitchcock,’’ which is partly based on Stephen Rebello’s book, ‘‘Alfred Hitchcock and the Making of Psycho,’’ Gervasi imagines the director communicating with Gein. A more complex picture of Hitchcock is also seen in the recent HBO film ‘‘The Girl,’’ which shows the making of ‘‘The Birds’’ and Hitchcock’s alleged tormenting of his star actress, Tippi Hedren.

Fearing a negative portrait, the Hitchcock estate didn’t allow the use of ‘‘Psycho’’ footage or dialogue for ‘‘Hitchcock.’’ But the film nevertheless takes pleasure in recreating and imagining the circumstances of making a film that still transfixes — that in shrill violin notes, shrieked a revolution.

‘‘It was a point in history where we were going from an idealistic, stylized imagination of what America could be, to this very visceral, brutal, violent period where the president is getting killed and people are getting assassinated,’’ says Gervasi. ‘‘Here we are 52 years later talking about the shock of a film. I mean, that’s a pretty powerful film.’’

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