Hesitation vowels: a motor speech respiration hypothesis

In spontaneous speech the relation of hesitation vowels 'ah' and 'mh' (filled pauses) and respiration was studied in 16 healthy native speakers of German. Hesitation vowels did not occur randomly in expiration during speech. When expiratory duration was divided into four segments of equal length, the highest incidence of hesitation vowels was to be found at early loci during expiration. As speech respiration is reset to vegetative breathing as soon as speech production stops, hesitation vowels act as phonomotoric subroutines during halting speech production to prevent the respiratory system from uneconomic air loss and to keep it in the speech respiration mode.