Rhythmic Versus Phonemic Interference in Delayed Auditory Feedback

Abstract

Purpose Delayed auditory feedback (DAF) of a speaker’s voice disturbs normal speech production. Various traditional theories assume that the content of the delayed feedback signal interferes with the actual production of a particular speech unit ( phonemic content hypothesis ). The displaced rhythm hypothesis as an alternative explanation suggests that speech disturbances arise from a disruptive rhythm that is produced by the delayed speech signal. The present experimental study directly contrasted the role of rhythm and speech content in a DAF task using speech units as stimuli. Method One hundred fifty-one participants read aloud 4 different sequences of double syllables that varied in phonemic content and rhythm while auditory feedback was either nondelayed or delayed by 200 or 400 ms. Results In line with previous studies, the authors found a peak of disturbances at a delay of about 200 ms, independent of speech rate. More important, the present results clearly support the displaced rhythm hypothesis. A speech rate dependency of this effect was also found. Conclusion Rhythm seems to be a significant criterion of speech monitoring, and hence a mismatch between spoken words and auditory feedback realized by DAF induces obvious speech problems on rhythmic level regardless of phonemic discrepancy at the same time.