"This is the true heart and soul of the Kuleshov effect. When we are shown no explicit emotion, we infer it--but in order to do that, we are forced to experience the circumstances, and feel the emotion ourselves. This is why the Kuleshov effect can generate such a strong reaction; it's why 2001 is such a powerful experience. We don't know HAL is frightened because he sounds frightened. We know he's frightened because Dave is coming to kill him. His blank voice forces us to experience his situation in his name and feel his own fear for him. We are one step closer to the action on screen, not reacting to the actors but reacting with the characters. "