First published in 1987. This book is about the processing of information. The central domain of interest is face-to-face communication in which the speaker makes available both audible and visible characteristics to the perceiver. Articulation by the speaker creates changes in atmospheric pressure for hearing and provides tongue, lip, jaw, and facial movements for seeing. These characteristics must be processed by the perceiver to recover the message conveyed by the speaker. The speaker and perceiver must share a language to make communication possible; some internal representation is necessarily functional for the perceiver to recover the message of the speak.