Hitchcock explains a few facets of film editing, including contrasting scale and context. Includes an example of the classic Russian experiment:
Sometime around 1918, Russian director Lev Kuleshov did an experiment that proves this point. (See Kuleshov Experiment) He took an old film clip of a head shot of a noted Russian actor and intercut the shot with a shot of a bowl of soup, then with a child playing with a teddy bear, then with a shot an elderly woman in a casket. When he showed the film to people they praised the actor’s acting—the hunger in his face when he saw the soup, the delight in the child, and the grief when looking at the dead woman.[2] Of course, the shot of the actor was years before the other shots and he never “saw” any of the items. The simple act of juxtaposing the shots in a sequence made the relationship. http://en.wikipedia.org/wiki/Film_editing