How fluency-enhancing conditions reduce stuttering. A unified explanation

Developmental stuttering is a speech disorder that affects about one percent of the adult population worldwide. The cause is still unknown, but not a few researchers have suspected poor auditory-motor integration to be a causal factor. Almost all people who stutter are more or totally fluent in certain conditions, for instance, when speaking in chorus or alone to themselves, in time with the clicking of a metronome, or with delayed or frequency-altered auditory feedback. Understanding why stuttering disappears in these specific conditions could help understand why it occurs in normal speaking conditions. Here, the first unified account for the effect is proposed, based on evidence that receptive speech processing depends on attention to the speech signal. It is proposed that fluency-enhancing conditions re-allocate the speaker’s attention, that is, the perceptual and processing capacities, by drawing attention to the auditory feedback of speech. This improves auditory-motor integration, which reduces stuttering. The hypothesis is discussed for all well-known fluency-enhancing conditions, and consequences for therapy are outlined.