Determining the influence of Gaussian blurring on inversion effects with talking faces

Perception of visual speech and the influence of visual speech on auditory speech perception is affected by the orientation of a talker’s face, but the nature of the visual information underlying this effect has yet to be established. Here, we examine the contributions of visually coarse (configural) and fine (featural) facial movement information to inversion effects in the perception of visual and audiovisual speech. We describe two experiments in which we disrupted perception of fine facial detail by decreasing spatial frequency (blurring) and disrupted perception of coarse configural information by facial inversion. For normal, unblurred talking faces, facial inversion had no influence on visual speech identification or on the effects of congruent or incongruent visual speech movements on perception of auditory speech. However, for blurred faces, facial inversion reduced identification of unimodal visual speech and effects of visual speech on perception of congruent and incongruent auditory speech. These effects were more pronounced for words whose appearance may be defined by fine featural detail. Implications for the nature of inversion effects in visual and audiovisual speech are discussed.