Acoustic determinants of phrase boundary perception.

How three supersegmental variables (amplitude, pitch contour, and duration pattern) influence phrase boundary perception was investigated in two studies. Listeners located the phrase boundary in ambiguous algebraic expressions, such as "(A plus E) times O" and A plus (E times O)." In one experiment, two values of each of three variables (appropriate or neutral) were orthogonally varied, using linear predictive coding analysis-synthesis procedures. There was a total of eight manipulations for each expression. In the other, the three suprasegmental variables were exchanged between the two alternative meanings of an expression, yielding a total of eight manipulations for each expression. Results from the two studies were consistent in showing that listeners use all three cues, and just these three to parse such utterances. That is, it was possible to completely shift the meaning of an expression uttered with one meaning into its alternate meaning by exchanging all three variables. In both studies, the effects of duration pattern and pitch contour were additive in total proportion correct. Possible models of how listeners process pitch and duration information independently in making a parsing decision are discussed.