Facial expression and prosodic prominence: Effects of modality and facial area

This article addresses two related questions regarding the perception of facial markers of prominence in spoken utterances: (1) how important are visual cues to prominence from the face with respect to auditory cues? and (2) are there differences between different facial areas in their cue value for prosodic prominence? The first perception experiment tackles the relation between auditory and visual cues by means of a reaction-time experiment. For this experiment, recordings of a sentence with three prosodically prominent words were systematically manipulated in such a way that auditory and visual cues to prominence were either congruent (occurring on the same word) or incongruent (in that the auditory and the visual cue were positioned on different words). Participants were instructed to indicate as fast as possible which word they perceived as the most prominent one. Results show that participants can more easily determine prominence when the visual cue occurs on the same word as the auditory cue, while displaced visual cues hinder prominence perception. The second experiment investigates which area of a speaker's face contains the strongest cues to prominence, using stimuli with either the entire face visible or only parts of it. The task of the participants was to indicate for each stimulus which word they perceived as the most prominent one. Results show that the upper facial area has stronger cue value for prominence detection than the bottom part, and that the left part of the face is more important than the right part. Results of mirror-images of the original fragments show that this latter result is due both to a speaker and an observer effect. (C) 2007 Elsevier Ltd. All rights reserved.