1. A method for adaptively determining the attitudinal function of a lexical item occurring in a natural language document, comprising: determining a base valence of the lexical item; identifying a contextual valence shifter (CVS) wherein the lexical item is within scope of the CVS; determining an actual valence of the lexical item by adjusting the base valence based on the CVS; and wherein the CVS is one of: reported speech/thought, elaboration, and genre.