The embodied character of cognitive motor systems that has greatly influenced the understanding of their constitution and function is reflected in many recent models. Embodiment conditions that system behaviours must take appropriate account of energy expenditure and metabolic costs that are unavoidable in a physically realised medium. We here consider that optimisation, presumed to result from both phylogenetic and ontogenetic processes, can be used to con strain the space of potential degrees of freedom of a system, ensuring that the resulting action is efficient and smooth. To understand the emerging adaptations, it is necessary to factor in the properties of the physical and physiological substrate that anchor the system's goal-oriented performance. However, the embodied nature of speech production has been disregarded by most phonological research to date. This leads to a failure in providing a coherent phonological grounding of a wide range of phenomena extensively documented by experimental phoneticians, in particular those associated with the relative timing of gestures (also called gestural phasing) in connected speech and its variability as found in different manners of speech. Existing phonological theories of sequencing rely on essentially external system-wide rules and principles or explicit dynamical constraints governing phasing to account for various suprasegmental properties and prosodic parameters of an utterance. We introduce here a new and highly abstract modelling platform developed to investigate the embodied character of speech. The physically instantiated, second-order dynamic nature of the system allows us to define and exactly evaluate various cost functions, which we hypothesise to play a role in efficient gestural sequencing. We investigate the general dynamical properties of the system, and identify a set of its high-level, intentional parameters linked to the cost functions associated with its goal-oriented performance. We show that the phenomena accompanying gestural sequencing, coarticulation, fluency and prosodic modulation emerge as consequences of a non-trivially formulated efficiency constraint, thus providing a principled phonological account of phonetic reality.

Inspec keywords: speech; optimisation; cognition

Other keywords: ontogenetic processes; phylogenetic processes; embodied speech gestures; prosodic parameters; suprasegmental properties; speech production; optimisation; phonological grounding; cognitive motor systems; physical substrate; physiological substrate

Subjects: Systems theory applications in social science and politics