The prosody of information units in spontaneous monologue

This article describes a perceptual evaluation of the prosodic structure of a spontaneously produced monologue. It was found that the speaker studied demarcates larger-scale topical units in spoken discourse by means of intonation (use of melodic boundary markers, scaling of maxima in pitch movements, general decline in average pitch) and by the use of pauses with variable durations. In a perception test, it was examined to what extent these prosodic devices may be important to listeners. Subjects were confronted with three unintelligible (band-pass-filtered) versions of a fragment of the elicited monologue: (1) with the original prosody unchanged; (2) with constant pause duration and the original speech melody; (3) with monotonous pitch and the original pause structure. They were instructed to indicate the boundaries of the larger-scale topical units in the three versions. Subjects were able to detect correctly the major discourse boundaries in all three filtered versions in a significant number of cases. They performed best when confronted with version 1. Versions 1 and 2, in their turn, did better than version 3, which suggests that, in the performance of this speaker, intonation is a perceptually more important factor than pause for the clarification of the topical make-up of a text, though the latter dimension is certainly not negligible.