The role of auditory feedback in speech and song.

When singing a melody or producing sentences, we take for granted the fact that the sounds we create (auditory feedback) match the intended consequences of our actions. The importance of these perception/action matches to production is illustrated by the detrimental effects of altered auditory feedback (AAF). Previous research in the domain of music has shown that when AAF leads to asynchronies between perception and action, timing of production is disrupted but accuracy of sequencing is not. On the other hand, AAF manipulations of pitch disrupt sequencing but not timing. Such dissociative effects, as well as other findings, suggest that sensitivity to AAF may be based on hierarchical organization of sequences. In the current research we examined whether similar effects are found for the production of speech, for which syllables rather than pitches may constitute content units. In the first experiment, participants either sang melodies or spoke sequences of nonsense syllables. In the second experiment, the tasks were combined such that participants sang syllable sequences. Production in both experiments was accompanied by either normal, asynchronous, or content altered auditory feedback. Across experiments, effects of AAF on the accuracy of sequencing were similar in speaking and singing tasks, and in all cases reflected the dissociative effects described earlier. For timing of production, however, previous results were only found when participants sang sequences that did not have varying syllabic content. These results suggest that sensitivity to timing exists at multiple hierarchical levels, particularly at the syllable and phonetic levels.