Impromptu speech is heard only once, at a rate of perception that depends on the speaker's delivery, and is specifically adapted to the listeners. These features trigger cognitive activities that facilitate translation. Impromptu speech is characterized by a constant interconnection between cognitive competence and language competence and between sound (prosodic, syntactic, and lexical features) and sense. A written text delivered orally does not have these characteristics and diminishes the listener's cognitive awareness. Impromptu delivery is characterized by the emission of sounds reflecting the speakers' thinking process; this is one of the major reasons that impromptu speech is easier to understand than prepared speech, and it is the reason that oral interpreters insist on speakers' speaking extemporaneously. (MSE)