Much of the genius of Alfred Hitchcock, of course, is that he understood -- perhaps better than any other filmmaker -- that the power of any movie came from the psychological as much as the visual chords that could be played. Which is why, nearly 50 years after its release in 1960, the 45-second shower scene in "Psycho" is still terrifying and paralyzing. And if you think it's scary on cable, try it again in the dark of a theater, where you can join in the communal scream when . . . well, maybe there's someone out there who hasn't seen it yet. On Wednesdays this month, the American Film Institute is celebrating the master at the ArcLight Hollywood. My favorite of his, "Rear Window," has already come and gone, but you can still catch "Psycho" next week and watch "The Birds" make the sky go dark with their beating wings the following one.