Speech perception without audition

Abstract

Most knowledge about speech perception is within the framework of studies concerned with acoustic-phonetic stimulus attributes. Vision is known to affect speech perception but is typically considered only as a supplement to hearing. The literature contains assertions that only 30% of words are recognized in lipreading/speechreading and that hearing subjects are more accurate than deaf subjects. Observations of expert visual speech perception among some profoundly deaf subjects [L. E. Bernstein et al., J. Acoust. Soc. Am. 90, 2971–2984 (1991)] promoted questioning of the conventional wisdom. A normative study of lipreading was therefore conducted involving 96 hearing and 72 deaf young adults. The two populations differed significantly across nonsense syllable, word, and sentence identification measures. The most accurate subjects were from within the deaf population. Results that lipreading in some deaf subjects is comparable to listening to speech in noise by hearing subjects. Expert lipreading demonstrates that speech perception does not require audition. Speech perception appears to be fundamentally the perception of linguistic entities not acoustic-phonetic attributes. Theories of speech perception for which generality is claimed need either to account also for visual speech perception or need to limit their claims to generality.