Test of the movement expansion model: anticipatory vowel lip protrusion and constriction in French and English speakers

Abstract

The modeling of anticipatory coarticulation has been the subject of longstanding debates for more than 40 yr. Empirical investigations in the articulatory domain have converged toward two extreme modeling approaches: a maximal anticipation behavior (Look-ahead model) or a fixed pattern (Time-locked model). However, empirical support for any of these models has been hardly conclusive, both within and across languages. The present study tested the temporal organization of vocalic anticipatory coarticulation of the rounding feature from [i] to [u] transitions for adult speakers of American English and Canadian French. Articulatory data were synchronously recorded using an Optotrak for lip protrusion and a dedicated Lip-Shape-Tracking-System for lip constriction. Results show that (i) protrusion is an inconsistent parameter for tracking anticipatory rounding gestures across individuals, more specifically in English; (ii) labial constriction (between-lip area) is a more reliable correlate, allowing for the description of vocalic rounding in both languages; (iii) when tested on the constriction component, speakers show a lawful anticipatory behavior expanding linearly as the intervocalic consonant interval increases from 0 to 5 consonants. The Movement Expansion Model from Abry and Lallouache [(1995a) Bul. de la Comm. Parlée 3, 85-99; (1995b) Proceedings of ICPHS 4, 152-155.] predicted such a regular behavior, i.e., a lawful variability with a speaker-specific expansion rate, which is not language-specific.

Figure 1

MEM predictions for the time course of protrusion (bold lines) and constriction (thin lines) from the vowel [i] to the rounded vowel [y] in French. The top signal is for the basic gesture for rounding in the simple sequence [iy], without an intervocalic obstruent consonant (or a silent pause). The three other signals, all aligned on the [y] acoustic onset (vertical dotted line), illustrate the expansion of the rounding movement—with the prediction of a linear expansion function—through sequences with an increasing number of intervocalic consonants (here up to five consonants in French; the same for English [i] to [u] sequences). OI, the obstruent consonant acoustic phase between the two vowels. Vertical arrows indicate the range of variation of the protrusion and constriction onsets (see text). Notice that protrusion will be inverted for comparison’s sake in the presentation of our data.

Figure 2

Illustration of the method employed to capture upper-lip protrusion (Optotrak IREDs on the vermillion boarder of the lower and upper lips) and labial area (constriction) via a blue lip shape tracking system.

Figure 3

Above: the waveform time (s); center: lip area time course (cm²); below: upper-lip protrusion time course (mm; inverted for visual correspondence with constriction) for a sequence [iksku] in the sentence “Deux kixes coukiquent” uttered by a Canadian French speaker in the BB condition. The OI is determined on the spectrogram by the acoustic offset of [i] and the acoustic onset of [u] formants. Identification of events on the lip area time course: 1 = maximal area for [i]; 2 = 10% of area difference between [i] and [u]; 3 = 90% of area range between [i] and [u]; 4 = minimal area for [u]; 5 = 10% of lip area difference between [i], and [u] following minimal area of [u]. Interval 2–3 corresponds to TF and interval 3–5 to the duration of the H phase. Identification of events on the upper-lip protrusion time course: 1 = minimal protrusion for [i]; 2 = 10% of protrusion difference between [i] and [u]; 3 = 90% of protrusion range between [i] and [u] ; 4 = maximal protrusion for [u]; 5 = 10% of protrusion difference between [i] and [u] following maximal protrusion of vowel [u]. Interval 2–3 also corresponds conventionally to the duration of protrusion TF and interval 3–5 to protrusion H.

Figure 4

Rounding anticipatory behavior for upper lip protrusion in four Canadian French speakers in bite-block (BB, right) and no-bite-block (NBB, left) conditions. Regression slopes and correlation coefficients (significant at p < 0.00001) between total duration of lip constriction movement [TF + H] and OI duration in seconds.

Figure 5

Rounding anticipatory behavior for upper-lip protrusion for the American English participant who displayed a sufficient protrusion in bite-block (BB, right) and no-bite-block (NBB, left) conditions. Regression slopes and correlation coefficients (significant at p < 0.00001) between total duration of lip constriction movement [TF + H] and OI duration in seconds.

Figure 6

Rounding anticipatory behavior for between-lip area (constriction) in four Canadian French participants in bite-block (BB, right) and no-bite-block (NBB, left) conditions. Correlations (significant at p < 0.0001) between total duration of lip constriction movement [TF + H] and OI duration in seconds.

Figure 7

Rounding anticipatory behavior for between-lip area (constriction) in four American English participants in bite-block (BB, right) and no-bite-block (NBB, left) conditions. Correlations (significant at p < 0.0001) between total duration of lip constriction movement [TF + H] and OI duration in seconds.

Figure 8

An overview of expansion rates (slopes) for American English (dotted-dashed lines) and Canadian French (solid lines) for protrusion (left) and constriction (right) in the bite-block condition. (Only one English speaker had measurable data for protrusion). The slope of 1 is predicted by the LA model, while zero slope is for TL model. For simplicity’s sake, slopes are shown to change from one consonant interval (vertical broken lines) to many.