
Categoricity, gradience, and timing: Variation at the phonetics-phonology interface
Ultimately, speech is produced through embodied physical movement in space and time that must be planned at some stage and executed at a subsequent stage of the speech production process. It is at this juncture between the properties of a speech plan and the properties of how that plan is implemented that many variable phenomena in speech production are ambiguously situated. The gradient properties of articulation, at the point of implementation, may give rise to variable outcomes in the signal, but mechanistic explanations for variation fail to account for the structurally-conditioned patterns that many such variables exhibit. On the other hand, descriptions of variables in terms of probabilistic—but categorical—outcomes from formal phonological machinery (e.g. Cedergren & Sankoff 1974; Guy 1991; Coetzee & Pater 2011) may account for their structural sensitivities, but make strong predictions about phonetic implementation across a finite set of discrete variants. I present results from my investigations into the articulation of a variable that is robustly attested across varieties of English: Coronal Stop Deletion, finding that cases of categorical deletion of the tongue tip raising gesture are rare, and it is the magnitude of these raising gestures that is gradiently conditioned by the morphological structure of the relevant word. This set of results is challenging to represent in segmental terms, but may be resolved indirectly through a reframing of the variable in terms of the articulatory timing properties of morphological boundaries. Together, these findings have broad implications for the representation of systematic variation at the phonetics-phonology interface.