The phonetic specificity of contrastive hyperarticulation in natural speech

Evidence suggests that speakers hyperarticulate phonetic cues to word identity in a way that increases phonetic distance to similar competitors. However, the degree and type of phonetic similarity between competitors which induces hyperarticulation remains unclear. Here, we compared neighborhood density (as a representative of a phonetically-general type of similarity) to the existence of a phonetic cue-specific lexical minimal pair in terms of their ability to predict hyperarticulation of two different cue-types in a corpus of natural English speech. For all phonetic cues that we investigated – word-initial voiceless stop VOT, word-initial voiced stop VOT, and vowel-vowel Euclidean formant distance – cue-specific minimal pair existence significantly predicted cue hyperarticulation, while neighborhood density did not. Further, the direction of change in a phonetic cue was found not to be consistent within a given cue-type, but instead varied as a function of the phonetic relationship, creating greater phonetic distance to the competitor. For tokens of word-initial voiceless stops, existence of a voiced-stop minimal pair predicted significantly longer VOT, while for word-initial voiced stops, existence of a voiceless-stop minimal pair predicted a shorter VOT. For tokens of vowels, existence of a minimal pair defined by a nearby vowel predicted greater Euclidean distance in formant space from that vowel, rather than greater expansion of the vowel space per se. For example, lax vowels in words with a more peripheral vowel minimal pair competitor (e.g., ship ∼ sheep) were relatively centralized, while tense vowels in words with a more interior vowel minimal pair competitor (e.g., date ∼ debt) were relatively peripheralized.