"Percephial centers" in speech production and perception.

Morton, Marcus, and Frankish (1976) report that listeners hear acoustically isochronous digit sequences as anisochronous. Moreover, given a chance to adjust intervals in the sequences until they are perceptually isochronous, the listeners introduce systematic deviations from isochrony. The present series of studies investigates these phenomena further. They indicate that when asked to produce isochronous sequences, talkers generate precisely the acoustic anisochronies that listeners require in order to hear a sequence as isochronous. The acoustic anisochronies that talkers produce are expected if talkers initiate the articulation of successive items in the sequence at temporally equidistant intervals. Items whose initial consonants differ in respect to manner class will have acoustic consequences (other than silence) at different lags with respect to their articulatory onsets thereby generating the observed acoustic anisochronies. The findings suggest that listeners judge isochrony based on acoustic information about articulatory timing rather than on some articulation-free acoustic basis.