Challenges with the kinematic analysis of neurotypical and impaired speech: Measures and models

A common goal of kinematic studies on disordered speech is the identification of speech motor impairments that negatively impact speech function. Although it is well-known that the kinematic contours of speakers with speech disorders often deviate considerably from those of neurotypical speakers, systematic quantitative assessments of these impairment-related movement disturbances remain challenging. Kinematic measurement approaches are commonly grounded in models and theories that have emerged exclusively from observations of healthy speakers. However, often these models cannot accommodate the deviant articulatory behaviors of speakers with speech motor impairment. In the present paper, we address this problem. By considering noise as a factor in Articulatory Phonology/Task Dynamics (AP/TD), we can account for articulatory behaviors that are known to occur in healthy speakers (e.g., during slow speech) as well as in speakers with motor speech impairments. In a proof of concept, we descriptively compare modeled articulatory behaviors that include noise at various levels with empirical data. We view such an extension of the AP/TD as a first step towards a more comprehensive speech production model that can serve as a theoretical framework to study the speech production mechanism in healthy speakers and speakers with motor speech impairments.