Perceiving speech from inverted faces.

We examined whether the orientation of the face influences speech perception in face-to-face communication. Participants identified auditory syllables, visible syllables, and bimodal syllables presented in an expanded factorial design. The syllables were /ba/, /va/, /oa/, or /da/. The auditory syllables were taken from natural speech whereas the visible syllables were produced by computer animation of a realistic talking face. The animated face was presented either as viewed in normal upright orientation or inverted orientation (180 degrees frontal rotation). The central intent of the study was to determine if an inverted view of the face would change the nature of processing bimodal speech or simply influence the information available in visible speech. The results with both the upright and inverted face views were adequately described by the fuzzy logical model of perception (FLMP). The observed differences in the FLMP's parameter values corresponding to the visual information indicate that inverting the view of the face influences the amount of visible information but does not change the nature of the information processing in bimodal speech perception.