Seeing and hearing rotated faces: influences of facial orientation on visual and audiovisual speech recognition

It is well-known that facial orientation affects the processing of static facial information, but similar effects on the processing of visual speech have yet to be explored fully. Three experiments are reported in which the effects of facial orientation on visual speech processing were examined using a talking face presented at 8 orientations through 360 degrees. Auditory and visual forms of the syllables /ba/, /bi/, /ga/, /gi/, /ma/, /mi/, /ta/, and /ti/ were used to produce the following speech stimulus types: auditory, visual, congruent audiovisual, and incongruent audiovisual. Facial orientation did not affect identification of visual speed per se or the near-perfect accuracy of auditory speech report with congruent audiovisual speech stimuli. However, facial orientation did affect the accuracy of auditory speech report with incongruent audiovisual speech stimuli. Moreover, the nature of this effect depended on the type of incongruent visual speech used. Implications for the processing of visual and audiovisual speech are discussed.