Lipreading supplemented by voice fundamental frequency: to what extent does the addition of voicing increase lexical uniqueness for the lipreader

Lipreading in combination with an acoustic indication of voice fundamental frequency (FO) has been shown to greatly improve word recognition accuracy with sentence stimuli. A possible explanation for this effect is that FO delivers information for consonantal voicing. In experiment 1 we showed with a computational model how voicing information affects the uniqueness of lipread words in a large phonemically transcribed machine-readable lexicon. In experiment 2 the same computational methods were used to simulate the results obtained by McGrath and Summerfield (1985) for lipreading with and without acoustic FO. The model failed to account in full for the behaviourally observed enhancements. It is suggested that lexical biasing in word recognition can account for the difference between the model and the behavioural results.