The relationship between head movements and speech dysfluencies

In four subjects, the correlations between dysfluencies in spontaneous speech and head movements, monitored by polarized-light goniometry, were studied in order to establish accurately their relative timing and the interaction between their linguistic and physical properties. Speech dysfluencies were categorized according to grammatical and physical properties, while head movements were classed as previously according to kinematic properties. Distinct head movement occurred after most dysfluencies, especially in association with large increases in loudness, showing significant correlations between movement classes and dysfluency categories. For instance, wide, linear movements (“postural shifts” or PS) tended to occur after “grammatical” pauses (between clauses or sentences); narrow, rapid movements (RM) tended to occur after dysfluencies inside grammatical boundaries, especially after short pauses. Findings were interpreted as consistent with previous speculations, assigning head movement a role in speech production, especially in dissipating energy and helping to co-ordinate movements of the articulators.