Towards a dynamical model of English vowels. Evidence from diphthongisation

TL;DR

This paper investigates whether diphthongs and long monophthongs in English form distinct categories or share a common articulatory basis, proposing a dynamic model that explains their relationship through gestural targets.

Contribution

It introduces an articulatory phonology model showing diphthongs and monophthongs share a common gestural representation, challenging traditional categorical distinctions.

Findings

Diphthongs are not categorically distinct from long monophthongs.

A two-target gestural model explains the variation in diphthongs and monophthongs.

Evidence from articulometry and acoustics supports a unified phonetic category.

Abstract

Diphthong vowels exhibit a degree of inherent dynamic change, the extent of which can vary synchronically and diachronically, such that diphthong vowels can become monophthongs and vice versa. Modelling this type of change requires defining diphthongs in opposition to monophthongs. However, formulating an explicit definition has proven elusive in acoustics and articulation, as diphthongisation is often gradient in these domains. In this study, we consider whether diphthong vowels form a coherent phonetic category from the articulatory point of view. We present articulometry and acoustic data from six speakers of Northern Anglo-English producing a full set of phonologically long vowels. We analyse several measures of diphthongisation, all of which suggest that diphthongs are not categorically distinct from long monophthongs. We account for this observation with an Articulatory Phonology/Task Dynamic model in which diphthongs and long monophthongs have a common gestural representation, comprising two articulatory targets in each case, but they differ according to gestural constriction and location of the component gestures. We argue that a two-target representation for all long vowels is independently supported by phonological weight, as well as by the nature of historical diphthongisation and present-day dynamic vowel variation in British English.