ABSTRACT
There is currently much debate and controversy concerning the nature of the acoustic information that is critical for speech perception and the nature of the processing mechanisms that map the relevant acoustic properties onto phonetic representations. However, even if these issues were to be resolved, we still would not have a complete account of phonetic perception. This is because, as Quentin Summerfield clearly describes (chapter 6 this volume), the perception of speech does not involve only the processing of acoustic information. Even in cases where neither the acoustic signal nor the listener's hearing is impoverished, observable articulatory movements on the talker's face provide phonetically relevant optic information that is used by the listener when perceiving speech.
