Motifs are generally so unobtrusive in a film that they can pass unnoticed even after repeated viewings. In Psycho, for example, Hitchcock employed the “doubles” motif with great density. The 2 pairs of leading actors (Janet Leigh/Vera Miles and Anthony Perkins/John Gavin) were cast according to physical resemblances, which suggest psychological similarities. Many of the scenes feature mirrors, which reinforce the doubles motif, as well as suggesting themes of reality versus illusion, truth versus deception, and conscious behavior versus impulse.
Giannetti, Louis D. Understanding Movies second edition. New Jersey, 1976.