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. 2022 Sep 12;65(9):3316-3336.
doi: 10.1044/2022_JSLHR-21-00450. Epub 2022 Aug 23.

A Cross-Sectional Age Group Study of Coarticulatory Resistance: The Case of Late-Acquired Voiceless Fricatives in English

Phil J Howson  1 , Melissa A Redford  2
Affiliations

A Cross-Sectional Age Group Study of Coarticulatory Resistance: The Case of Late-Acquired Voiceless Fricatives in English

Phil J Howson et al. J Speech Lang Hear Res. .

Abstract

Purpose: As a class, fricatives are more "resistant" to consonant-vowel coarticulation than other English sounds. This study investigates the relative coarticulatory resistance of /θ, s, ʃ/ in child and adult speech to better understand the acquisition of individuated speech sounds.

Method: Ten 5-year-old children, seven 8-year-old children, and nine college-age adults produced [əFV] sequences in carrier phrases, where F was /θ/, /s/, or /ʃ/ and V was /æ/, /i/, or /u/. In Experiment 1, coarticulation was perceptually indexed: 65 adults predicted the target stressed vowel based on forward-gated audiovisual speech samples for a subset of four speakers from each age group. In Experiment 2, dynamic spectral measures of the /əFV/ sequences were analyzed using smoothing spline analysis of variance to again test for vowel effects on fricative articulation across age groups.

Results: The perceptual results indicated that fricatives blocked vowel-vowel coarticulation across speaker age groups. Contrary to expectation, vowels were most accurately predicted when F was /s/ and not when it was /ʃ/ or /θ/ across age groups. Acoustic results indicated the expected biomechanically motivated /ʃ/ > /s/ > /θ/ coarticulatory resistance hierarchy in adults' speech. By contrast, /ʃ/ > /s/ were similarly influenced by context in 8-year-olds' speech, and the results from 5-year-olds' speech suggested an influence of order of acquisition in that /θ/ was surprisingly resistant to coarticulation.

Conclusion: The study results are taken to suggest that a temporal constraint on fricative articulation interacts with biomechanical constraints during development to influence patterns of coarticulation in school-age children's speech.

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Figures

Figure 1.
Figure 1.
The final frame for each cut from one repetition of a 5-year-old's production of I bought the she hat (aj b|1 ɑ|2 tθ|3 ə|4 ʃ|5 i|6 hæt).
Figure 2.
Figure 2.
Rand index (ACC) by gate, fricative condition, and the speakers' age groups. The dotted line on the plot indicates the threshold for being above or below chance.
Figure 3.
Figure 3.
Rand index (ACC) by gate and the speakers' age groups. The dotted line on the plot indicates the threshold for being above or below chance.
Figure 4.
Figure 4.
Trajectories for adult /əθV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /θ/ (center). Color coding is by vowel target.
Figure 5.
Figure 5.
Trajectories for adult /əsV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /s/ (center). Color coding is by vowel target.
Figure 6.
Figure 6.
Trajectories for adult /əʃV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /ʃ/ (center). Color coding is by vowel target.
Figure 7.
Figure 7.
Trajectories for 8-year-old /əθV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /θ/ (center). Color coding is by vowel target.
Figure 8.
Figure 8.
Trajectories for 8-year-old /əsV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /s/ (center). Color coding is by vowel target.
Figure 9.
Figure 9.
Trajectories for 8-year-old /əʃV/ sequences: Formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /ʃ/ (center). Color coding is by vowel target.
Figure 10.
Figure 10.
Trajectories for 5-year-old /əθV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /θ/ (center). Color coding is by vowel target.
Figure 11.
Figure 11.
Trajectories for 5-year-old /əsV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /s/ (center). Color coding is by vowel target.
Figure 12.
Figure 12.
Trajectories for 5-year-old /əʃV/ sequences: formant trajectories for schwa (left) and target vowel (right); center of gravity trajectories for /ʃ/ (center). Color coding is by vowel target.
Figure 13.
Figure 13.
Box plots of root-mean-square error for Age Group × Fricative. RMSE = root-mean-square error.
Figure 14.
Figure 14.
Raw accuracy measures for /i/ (left), /æ/ (middle), and /u/ (right) for each fricative /s/ (top), /ʃ/ (middle), and /θ/ (bottom). Adults are in blue, 8-year-olds are in green, and 5-year-olds are in red.
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