Phone rate and the effective planning time hypothesis of stuttering.

Effects on syllable disfluency and phone rate (duration of phones spoken per minute) were compared in 19 adult stutterers under three reading rate conditions: control; slow normally-spoken-word-syllable timed (WS); and phone-prolongation (PP) matched to WS in syllable rate. Both phone rate and syllable disfluency were progressively reduced from control to WS to PP conditions. These results strongly support the discoordination hypothesis that any condition which facilitates initiation of phonation in coordination with articulation and respiration will reduce stuttering. A broader hypothesis is that effective planning time for voice onset coordinations is the common element that explains the power of retarded phone rate, reduction of phonatory complexity, and rhythm virtually to eliminate stuttering.