The breadth of coarticulatory units in children and adults

Abstract

Purpose: To assess, in children and adults, the breadth of coarticulatory movements associated with a single rounded vowel.

Method: Upper and lower lip movements were recorded from 8 young adults and 8 children (aged 4-5 years). A single rounded versus unrounded vowel was embedded in the medial position of pairs of 7-word/7-syllable sentences.

Results: Both children and adults produced movement trajectories associated with lip rounding that were very broad temporally (i.e., movement duration lasting 45% to 56% of the sentence). Some effects appeared to extend across the entire utterance. There were no differences between children and adults in the extent of the coarticulatory effect. However, children produced relatively variable movements associated with lip rounding.

Conclusions: These data support the hypothesis that, for young children and adults, broad chunks of output have been planned by the onset of implementation of a sentence. This implies that, based on a change in a single phoneme, the motor commands to the muscles are altered for the production of the entire sentence.

Figure 1

Example of extracted movement sequence from a child producing the target sentence “Mom has the boot in the box.” The top panel shows the superior–inferior (SI) displacement record associated with lower lip + jaw movement, and the middle panel depicts the derived velocity record. These two panels illustrate how movements for the utterance were extracted, beginning with the peak velocity in the opening movement for mom and ending with the peak velocity for the opening movement in box. The bottom panel shows the time-locked record for upper lip anterior–posterior (AP) movement (i.e., lip rounding). The dotted lines at the onset and offset of the sentence show the portion of the upper lip AP movement used in all analyses.

Figure 2

Method for assessing the degree of lip protrusion. The solid line shows an utterance containing the word goose, with minimum (min) and maximum (max) values identified. The dotted line shows an example of the sentence containing the word geese. The lip protrusion measure was determined by subtracting the minimum from the maximum in the upper lip AP displacement.

Figure 3

Example of the spatiotemporal index for child productions of sentences containing the words goose and geese. These upper lip AP records were collected from the entire utterance, as shown in Figure 1. The top panel illustrates the original, non-normalized records; the middle panel illustrates the same records, now time- and amplitude-normalized; and the bottom panel illustrates the spatiotemporal index (STI).

Figure 4

Example of the spatiotemporal index for adult productions of sentences containing the words goose and geese. These upper lip AP records were collected from the entire utterance, as shown in Figure 1. The top panel illustrates the original, non-normalized records; the middle panel illustrates the same records, now time- and amplitudenormalized; and the bottom panel illustrates the STI.

Figure 5

Method for assessing how total normalized area of difference between rounded and unrounded conditions was calculated. A normalized average template of the upper lip AP movement for 10 productions of sentences containing the word goose is shown overlaying the average template for the upper lip AP movement for 10 sentences containing the word geese. The vertical lines are illustrative of the areas included in the integrative sum. A point-by-point difference score was obtained in the regions denoted.

Figure 6

Method for assessing how the temporal extent of the lip rounding effect was determined. The normalized template from the control condition served as a comparison for assessing when the rounding movement began and ended. Each individual sentence containing a rounded vowel (thin solid line; in this example, goose) was assessed in comparison with the template for the sentence containing the unrounded vowel (thick dashed line; in this example, geese).

Figure 7

Lip protrusion displacement values (in mm) of upper lip AP movements associated with rounded (filled shapes) and unrounded (open shapes) targets. Error bars represent standard errors.

Figure 8

STI values of upper lip AP movements associated with rounded (filled shapes) and unrounded (open shapes) targets. Error bars represent standard errors.

Figure 9

Total normalized area of the difference between rounded and unrounded conditions. Error bars represent standard errors.