Effects of timing regularity and metrical expectancy on spoken-word perception.

Certain types of speech, e.g. lists of words or numbers, are usually spoken with highly regular inter-stress timing. The main hypothesis of this study (derived from the Dynamic Attending Theory) is that listeners attend in particular to speech events at these regular time points. Better timing regularity should improve spoken-word perception. Previous studies have suggested only a weak effect of speech rhythm on spoken-word perception, but the timing of inter-stress intervals was not controlled in these studies. A phoneme monitoring experiment is reported, in which listeners heard lists of disyllabic words in which the timing of the stressed vowels was either regular (with equidistant inter-stress intervals) or irregular. In addition, metrical expectancy was controlled by varying the stress pattern of the target word, as either the same or the opposite of the stress pattern in its preceding words. Resulting reaction times show a main effect of timing regularity, but not of metrical expectancy. These results suggest that listeners employ attentional rhythms in spoken-word perception, and that regular speech timing improves speech communication.