Dialogue authenticates the speaker as an individual or a real person rather than the imaginary creation of a story teller. As is the case with stage drama, dialogue serves to tell the story and
expresses feelings and motivations of characters as well. Often with film characterization the audience perceives little or no difference between the character and the actor. Thus, for example:
Humphrey Bogart is Sam Spade; film personality and life personality seem to merge. Perhaps this is the case because the very texture of a performer's voice supplies an element of character.