According to
Roger Ebert, Lumet had a theory about why
Marlon Brando's performances were so uneven. In a review of a bad film starring Brando, Ebert outlined this idea in detail: Lumet said that on the first scene he filmed for any director, Brando would do exactly two takes. In one of the takes, Brando would be putting technical skill and background research into his reading, and in the other he would simply recite his lines as blandly as possible. If the director used the bland take, Brando would proceed to sleepwalk though his performance for the entirety of filming.
