A frequent acoustic sign of speech motor delay (SMD)

Figures & data

Table 1. Description of target participants in three groups of speakers with Speech Motor Delay (SMD) and control participants in two of the three groups. The lower three rows include information on participants in three databases of speakers with typically-developing speech used to standardize measures.

		No. of participants		Age (yrs)		Gender		PCC		PVC
Group	n	SMD	No MSD	M	SD	Male	Female	M	SD	M	SD	Dialect	Speech and Motor Speech Classification
USA^a	415	50		5.1	1.7	40	10	71.8	14.3	91.9	6.1	General American	Idiopathic Speech Delay
			341	4.8	1.7	238	103	74.5	12.2	93.6	4.4	General American	Idiopathic Speech Delay and No Motor Speech Disorder
CND^b	346	87		15.4	11.2	49	38	88.6	10.0	96.2	4.7	General American	Eight types of complex neurodevelopmental disorders
			181	11.7	10.6	114	67	92.8	7.0	97.9	2.5	General American	Eight types of complex neurodevelopmental disorders and No Motor Speech Disorder
ALSPAC^c	156	9		8.8	0.4	*	*	98.5	1.8	99.8	0.4	Bristol, England	Persistent Idiopathic Speech Delay
Reference Databases
USA^d	150	̶		10.4	4.3	75	75					General American	Typically-developing speakers
CND^e	200	̶		21.0	20.2	100	100					General American	Typically-developing speakers
ALSPAC	25	̶		8.9	0.4	12	13					Bristol, England	Typically-developing speakers

Note: *These cells contain figures less than 5 and cannot be shown due to risk of loss of anonymity.

ALSPAC = Avon Longitudinal Study of Parent and Children, CND = Complex Neurodevelopmental Disorder, No MSD = No Motor Speech Disorder, PCC = Percentage of Consonants Correct, PVC = Percentage of Vowels Correct.

^a Shriberg, Campbell, et al. (2019).

^b Shriberg, Strand, et al. (2019). The eight types of CND include: 16p11.2 deletion and duplication syndrome; 22q11.2 deletion syndrome; Autism Spectrum Disorder; Down syndrome; fragile X syndrome; Galactosemia; Idiopathic Intellectual Disorder; Severe Traumatic Brain Injury.

^c Wren et al. (2013); Wren et al. (2016).

^d Potter et al. (2012).

^e Potter et al. (2012) and Scheer-Cohen et al. (2013).

Figure 1. The Precision-Stability Index (PSI).

Figure 2. Acoustic signs of Speech Motor Delay in three study groups. The groups are USA = United States of America, CND = Complex Neurodevelopmental Disorders, and ALSPAC = Avon Longitudinal Study of Parents and Children.

Table 2. PSI Sign No. 5 findings for participants in the USA and Complex Neurodevelopmental Disorder (CND) groups with idiopathic Speech Delay and Speech Motor Delay (SMD) compared to control participants with idiopathic Speech Delay and No Motor Speech Disorder (No MSD) in two speech tasks.

		PSI Sign No. 5: Vowel/Diphthong Duration (ms)^a
		SMD			No MSD			Inferential Statistics
Group	Speech Task	n	M	SD	n	M	SD	Effect Size^b	Confidence Interval
USA									Lower	Upper
	Continuous Speech	50	169.2	43.3	341	147.8	32.0	0.63*	0.33	0.94
	Word Imitation	23	207.2	53.7	82	210.2	51.5	−0.06	−0.52	0.41
CND
	Continuous Speech	87	139.4	38.8	181	125.0	30.7	0.43*	0.17	0.69
	Word Imitation	11	220.6	37.6	11	186.0	15.6	1.16*	0.25	2.06

^a PSI Sign No. 5 = Precision-Stability Index Sign No. 5: Increased duration of mid-vowels and diphthongs.

^b * = Significant Hedges-corrected effect size (Hedges & Olkin, 1985).

Figure 3. Average duration (ms) of the 11 phonemes in PSI 5: Increased Duration of Mid-Vowels and Diphthongs in the continuous speech tasks from participants with idiopathic Speech Delay (SD) and Speech Motor Delay compared to durations of these phonemes from the continuous speech of participants with SD and No Motor Speech Disorder (see text).

Shriberg, L. D., Campbell, T. F., Mabie, H. L., & McGlothlin, J. H. (2019). Initial studies of the phenotype and persistence of Speech Motor Delay (SMD). Manuscript submitted for publication.

 Google Scholar

Shriberg, L. D., Strand, E. A., Jakielski, K. J., & Mabie, H. L. (2019). Estimates of the prevalence of speech and motor speech disorders in persons with complex neurodevelopmental disorders. Manuscript submitted for publication.

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Wren, Y., McLeod, S., White, P., Miller, L. L., & Roulstone, S. (2013). Speech characteristics of 8-year-old children: Findings from a prospective population study. Journal of Communication Disorders, 46, 53–69. doi:10.1016/j.jcomdis.2012.08.008

 PubMed Web of Science ®Google Scholar

Wren, Y., Miller, L. L., Peters, T. J., Emond, A., & Roulstone, S. (2016). Prevalence and predictors of persistent speech sound disorder at eight years old: Findings from a population cohort study. Journal of Speech, Language, and Hearing Research, 59, 647–673. doi:10.1044/2015_JSLHR-S-14-0282

 PubMed Web of Science ®Google Scholar

Potter, N. L., Hall, S., Karlsson, H. B., Fourakis, M., Lohmeier, H. L., McSweeny, J. L., … Shriberg, L. D. (2012). Reference Data for the Madison Speech Assessment Protocol (MSAP): A Database of 150 Participants 3-to-18 Years of Age with Typical Speech. ( Technical Report No. 18). Phonology Project, Madison, WI: Waisman Center, University of Wisconsin–Madison. Retrieved from Phonology Project website: http://www.waisman.wisc.edu/phonology/

 Google Scholar

Scheer-Cohen, A. R., Holt, A. S., Karlsson, H. B., Mabie, H. L., McSweeny, J. L., Tilkens, C. M., & Shriberg, L. D. (2013). Reference Data for the Madison Speech Assessment Protocol (MSAP): A Database of Fifty 20-to-80 year old Participants with Typical Speech. (Technical Report No. 20). Phonology Project, Madison, WI: Waisman Center, University of Wisconsin–Madison. Retrieved from Phonology Project website: http://www.waisman.wisc.edu/phonology/

 Google Scholar

Hedges, L. V., & Olkin, I. (1985). Statistical methods for metaanalysis. Boston, MA: Academic Press.

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