Effects of horizontal viewing angle on visual and audiovisual speech recognition

The authors investigated the effects of changes in horizontal viewing angle on visual and audiovisual speech recognition in 4 experiments, using a tal ker's face viewed full face, three quarters, and in profile. When only expe rimental items were shown (Experiments 1 and 2). identification of unimodal visual speech and visual speech influences on congruent and incongruent au ditory speech were unaffected by viewing angle changes. However, when exper imental items were intermingled with distractor items (Experiments 3 and 4) , identification of unimodal visual speech decreased with profile views, wh ereas visual speech influences on congruent and incongruent auditory speech remained unaffected by viewing angle changes. These findings indicate that audiovisual speech recognition withstands substantial changes in horizonta l viewing angle, but explicit identification of visual speech is less robus t. Implications of this distinction for under-standing the processes underl ying visual and audiovisual speech recognition are discussed.