Leigh Lisker and Arthur Abramson look for simplification at the level of articulatory action in the voicing of certain contrasting consonants (/b/, /d/, /g/ vs. /p/, /t/, /k/). They show by acoustic measurements in eleven languages and by cross-language perceptual studies with synthetic speech that many acoustic properties of voicing contrasts arise from variations in voice onset time, that is, in the relative phasing of the onset of vocal cord vibration and the end of a consonant. Their work is widely replicated and elaborated, here and abroad, over the following decades.
Donald Shankweiler and Michael Studdert-Kennedy introduce dichotic listening into speech research, presenting different nonsense syllables simultaneously to opposite ears. They demonstrate dissociation of phonetic (speech) and auditory (nonspeech) perception by finding that phonetic structure devoid of meaning is an integral part of language, typically processed in the left cerebral hemisphere. Their work is replicated and developed in many laboratories over following years.
Alvin Liberman, Cooper, Shankweiler, and Studdert-Kennedy summarize and interpret fifteen years of research in “Perception of the Speech Code,” [PDF] still among the most cited papers in the speech literature. It sets the agenda for many years of research at Haskins and elsewhere by describing speech as a code in which speakers overlap (or coarticulate) segments to form syllables. These units last long enough to be resolved by the ear of a listener, who recovers segments from syllables by means of a specialized decoder in the brain’s left hemisphere that is formed from overlapping input and output neural networks—a physiologically grounded “motor theory.”
Haskins acquires its first computer (a Honeywell DDP224) and connects it to a speech synthesizer designed and built by the Laboratories’ engineers. Ignatius Mattingly, with British collaborators John N. Holmes and J. N. Shearme, adapts the Pattern Playback rules to write the first computer program for synthesizing continuous speech from a phonetically spelled input. A further step toward a reading machine for the blind combines Mattingly’s program with an automatic look-up procedure for converting alphabetic text into strings of phonetic symbols.