http://rogerebert.suntimes.com/apps/pbcs.dll/article?AID=/19981206/REVIEWS08/401010353/1023

For thoughtful viewers, however, an equal surprise is still waiting. That is the mystery of why Hitchcock marred the ending of a masterpiece with a sequence that is grotesquely out of place. After the murders have been solved, there is an inexplicable scene during which a long-winded psychiatrist (Simon Oakland) lectures the assembled survivors on the causes of Norman's psychopathic behavior. This is an anticlimax taken almost to the point of parody.

If I were bold enough to reedit Hitchcock's film, I would include only the doctor's first explanation of Norman's dual personality: "Norman Bates no longer exists. He only half existed to begin with. And now, the other half has taken over, probably for all time." Then I would cut out everything else the psychiatrist says, and cut to the shots of Norman wrapped in the blanket while his mother's voice speaks ("It's sad when a mother has to speak the words that condemn her own son..."). Those edits, I submit, would have made "Psycho" very nearly perfect. I have never encountered a single convincing defense of the psychiatric blather; Truffaut tactfully avoids it in his famous interview.