Initial studies of the phenotype and persistence of speech motor delay (SMD)

Figures & data

Table 1. Motor speech classifications and demographic, cognitive-language, and speech information for 415 participants with Speech Delay.

		Demographic					Cognitive-Language				Speech
		Age (yrs)			Sex (%)		Cognition^a		Language^b		PCC^c		II^d
Motor Speech Classification	n	M	SD	Range	Female	Male	M	SD	M	SD	M	SD	M	SD
No MSD	341	4.8	1.7	3–16	30.0	70.0	100.6	14.2	96.1	15.6	74.5	12.2	92.1	7.8
SMD	50	5.1	1.7	3–10	20.0	80.0	100.6	12.1	97.2	13.6	71.8	14.3	88.8	10.2
CD	14	4.7	1.6	3–8	21.4	78.6	109.8	11.1	105.0	17.0	70.0	14.8	83.4	14.6
CAS	10	5.0	1.7	3–9	20.0	80.0	63	* ^e	77	* ^e	76.3	9.6	84.4	15.1
Total/Average	415	4.9	1.7	3–16	28.4	71.6	100.8	14.1	96.6	15.4	74.1	12.6	91.2	8.8
Group-Averaged		4.9	1.7		22.9	77.2	93.5	12.5	93.8	15.4	73.2	12.7	87.2	11.9

Notes: PCC = Percentage of Consonants Correct; II = Intelligibility Index; No MSD = No Motor Speech Disorder; SMD = Speech Motor Delay; CD = Childhood Dysarthria; CAS = Childhood Apraxia of Speech.

^a Scores for Cognition: IQ Composite (n = 25) from Kaufman Brief Intelligence Test – Second Edition; Kaufman and Kaufman (2004).

Total Score Standard Score (General Ability; n = 64) from Detroit Tests of Learning Aptitude-Primary: Third Edition; Hammill and Bryant (2005).

Full IQ (n = 16) from Weschler Abbreviated Scale of Intelligence; Wechsler (1999).

^b Scores for Language: Oral Composite Standard Score (n = 27) from Oral and Written Language Scales (OWLS); Carrow-Woolfolk (1995).

Oral Composite Standard Score (n = 66) from Oral and Written Language Scales, Second Edition (OWLS-II); Carrow-Woolfolk (2011).

Core Language Standard Scores (n = 23) from Clinical Evaluation of Language Fundamentals-4 (CELF–4); Semel, Wiig, and Secord (2003).

^c Shriberg et al. (1997).

^d Shriberg (1993).

^e Standardized cognition and language measures available for only one participant.

Table 2. Demographic, language, and speech information for 14 participants in treatment for idiopathic Speech Delay.^a.

		Sex			Speech
Participant	Age (yrs;mos)	Female	Male	Language^b	PCC^c	II^d
1	3;1		X	PPVT-R SS: 99 PLS: Auditory Comprehension Quotient: 100; Verbal Ability Quotient: 87	53.4	82.9
2	3;6		X	OWLS: Oral Composite SS: 99	61.7	81.8
3	3;6		X	PPVT-R SS: 66 TOLD-P: Subtest I SS: 63; Subtest II: 16; Subtest III: 9; Subtest IV: 9; Subtest V: 9	66.5	76.6
4	3;10		X	*	68.2	70.4
5	4;1		X	PPVT-R SS: 95	63.1	80.6
6	4;2		X	*	80.1	95.2
7	4;4		X	OWLS: Oral Composite SS: 101	70.9	96.2
8	4;5		X	PLS-3: Receptive: 76; Expressive: 67	42.1	75.2
9	4;7		X	*	80.1	95.4
10	5;0	X		*	71.3	96.2
11	5;1		X	*	73.8	73.2
12	5;4		X	PPVT-R Percentile: 99th	66.7	97.2
13	5;7	X		PPVT-R: Age equivalent 4;9 The Miller-Yoder Test of Grammatical Comprehension: ‘passed all 5 and 6 year level items’ The Token Test for Children: scored within age level on all 5 subtests	67.4	100.0
14	5;9		X	*	82.9	91.8
Mean	4;5				67.7	86.6
SD	10 mos				10.8	10.4
%		14.3	85.7

Notes: PPVT-R = Peabody Picture Vocabulary Test-Revised; SS = Standard Score; PLS = Preschool Language Scale; OWLS = Oral and Written Language Scales; TOLD-P = Test of Language Development-Primary; PLS-3 = Preschool Language Scale-3; II = Intelligibility Index and PCC = Percentage of Consonants Correct.

^a Participants are ordered by age at first assessment: language and speech data were obtained at the same or approximate age. All speech data were obtained from retrospective longitudinal audio-recordings.

^b Peabody Picture Vocabulary Test-Revised (Dunn & Dunn, 1981); Preschool Language Scale (Zimmerman, 1969); Oral and Written Language Scales (Carrow-Woolfolk, 1995); TOLD-P = Test of Language Development-Primary (Newcomer & Hammill, 1988); Preschool Language Scale-3 (Zimmerman, Steiner, & Pond, 1992); The Miller-Yoder Test of Grammatical Comprehension (Miller & Yoder, 1975); The Token Test for Children (DiSimoni, 1978). * = no data.

^c Shriberg et al. (1997).

^d Shriberg (1993).

Table 3. Description of participant samples with high (Sample 1) and low (Sample 2) prevalence of Speech Motor Delay (SMD).^a.

	Sample 1: High Prevalence of SMD (22.4%)				Sample 2: Low Prevalence of SMD: (2.8%)				Between-group Comparisons
Variable	n	M	SD	%	n	M	SD	%	Confidence Interval	Effect Size^b	p-value^c
Demographic
Age (yrs)	67	5.1	1.5		72	4.0	0.7		0.59, 1.30	0.95 L
Gender (male)				77.6				73.6			0.694
Parent Report-Risk Factors
Speech, Language, & Learning
Articulation/Phonology	60			92.3	44			68.8			0.001
Apraxia	6			9.2	3			4.8			0.492
Dysarthria	3			4.6	0			0.0			0.244
Receptive language disorder	7			10.8	2			2.9			0.090
Expressive language disorder	17			26.2	3			4.8			0.001
Structural disorder	5			7.7	2			3.1			0.440
Fluency disorder	6			9.2	1			1.4			0.057
Voice Disorder	3			4.6	1			1.5			0.358
Other Disorder	4			6.2	0			0.0			0.058
Learning disability	3			4.5	3			4.2			1.000
Hearing
History of hearing problems	5			7.7	4			5.7			0.738
OME 16+ in first 18 months	2			3.4	4			6.8			0.679
PE tubes placed	11			16.4	9			12.5			0.630
Genetics
Nuclear family member with verbal trait disorder	32			49.2	31			46.3			0.862
Cognitive-Linguistic
Syllable Repetition Task^d
Performance	66	−1.16	1.42		71	−0.58	1.02		−0.81, −0.13	−0.47 S
Encoding	66	−0.44	1.09		69	−0.14	1.03		−0.62, 0.06	−0.28
Memory	67	−1.01	1.78		72	0.13	0.81		−1.18, −0.48	−0.83 L
Language
Average Words/Utterance-Z	67	−1.38	1.14		72	−1.94	1.03		0.18, 0.85	0.51 M
Speech
PCC	67	80.6	11.2		72	70.0	9.6		0.66, 1.37	1.01 V
PCC-Z	67	−1.86	1.58		72	−2.44	1.19		0.08, 0.75	0.41 S
PVC	67	93.3	5.3		72	91.7	5.3		−0.03, 0.63	0.30
PVC-Z	67	−2.61	2.01		72	−3.21	1.71		−0.01, 0.66	0.32
II	67	94.4	7.2		72	88.5	8.9		0.38, 1.07	0.72 M
II-Z	67	−1.79	2.10		72	−3.54	1.94		0.51, 1.21	0.86 L
OII^e: % Lowered Intelligibility				10.4				23.6			0.046

Notes: OME = Otitis Media with Effusion; PE = Pressure Equalization; PCC-Z = Percentage of Consonants Correct-Z-score; PVC = Percentage of Vowels Correct; PVC-Z = Percentage of Vowels Correct-Z-score; II-Z = Intelligibility Index-Z-score; OII = Ordinal Intelligibility Index.

^a See text for description of treatment histories for each group. Statistically significant findings are bolded.

^b Effect Size: Small (S) >0.2; Medium (M) >0.5; Large (L) >0.8; Very Large (V) >1.0.

^c Fisher’s exact tests.

^d Shriberg and Lohmeier (2008).

^e Mabie and Shriberg (2017). Lowered intelligibility: <85%.

Table 4. Ten most frequent earliest available PSI signs for participants with Speech Motor Delay (SMD) and with No Motor Speech Disorder (No MSD).

System	Domain			Data Reduction		% of Participants Positive on Sign		Attributes
		PSI Sign No.	PSI Sign Description	Perceptual	Acoustic	SMD	No MSD	Precision	Stability	Spatial	Temporal
Speech	Vowels
		5	Increased Duration for Mid-Vowels and Diphthongs		X	56.0	25.0	X			X
		6	Reduced % Vowel Phoneme Target Consistency	X		65.0	32.4		X	X
		7	Reduced % Vowel Target Consistency	X		66.7	28.7		X	X
	Consonants
		8	Reduced % Correct Glides	X		52.0	31.7	X		X
		12	Decreased 1st Moment on/s/Initial Singletons		X	53.3	47.7		X	X
	Vowels & Consonants
		17	Increased Diacritic Modification Index Class: Duration %	X		54.0	24.3	X			X
		18	Increased % of Epenthesis Errors	X		60.0	33.1	X		X
Prosody	Rate
		21	Increased Average Syllable Duration (ms) (without pauses)		X	52.0	7.7	X			X
	Stress
		23	Increased % of Prosody-Voice Codes15/16 Excessive Equal codes of all Prosody-Voice Codes 15/16 (uncircled & circled)	X		52.3	11.1	X			X
Voice	Laryngeal Quality
		29	Decreased Harmonic-to-Noise Ratio (dB) for Vowels		X	52.0	16.5	X		^__a	^__a
			Totals	6	4			7	3	5	4
			Mean (SD)			56.3 (5.6)	25.8 (11.8)

Notes: PSI = Precision-Stability Index; ms = millisecond; dB = decibel.

^a Indeterminate.

Table 5. Information for participants with Speech Motor Delay (SMD) and participants with No Motor Speech Disorder (No MSD).^a.

	SMD				No MSD				Inferential Statistics
Variable	n	M	SD	%	n	M	SD	%	Confidence Interval	Effect Size^b	p-value^c
Demographic
Age (yrs)	50	5.1	1.7		341	4.8	1.7		−0.12, 0.47	0.18
Gender (male)				80.0				70.0			0.181
Parent Report-Risk Factors
Speech, Language, & Learning
Articulation/Phonology	19			94.7	129			79.8			0.200
Apraxia	19			15.8	128			7.0			0.189
Dysarthria	19			0.0	130			2.3			1.000
Receptive language disorder	20			15.0	133			7.5			0.380
Expressive language disorder	19			36.8	127			14.2			0.023
Structural disorder	19			5.3	130			4.6			1.000
Fluency disorder	20			10.0	133			4.5			0.281
Voice Disorder	20			5.0	132			2.3			0.435
Other Disorder	19			0.0	131			3.1			1.000
Learning disability	22			4.5	137			3.6			1.000
Hearing
History of hearing problems	20			5.0	134			9.0			1.000
OME 16+ in first 18 months	18			0.0	119			5.0			1.000
PE tubes placed	22			18.2	137			15.3			0.754
Genetics
Nuclear family member with verbal trait disorder	20			30.0	132			48.5			0.152
Cognitive-Linguistic
Syllable Repetition Task^d
Performance	24	−1.18	1.39		174	−0.83	1.36		−0.68, 0.17	−0.26
Encoding	25	−0.71	0.79		171	−0.25	1.10		−0.85, −0.01	−0.43 S
Memory	25	−1.02	1.91		177	−0.49	1.48		−0.76, 0.08	−0.34
Language
OWLS: Oral Composite^e	20	97.2	13.6		58	94.7	14.4		−0.33, 0.68	0.17
Average Words/Utterance	50	−1.43	0.97		341	−0.93	1.44		−0.66, −0.06	0.36 S
Speech
PCC	50	71.8	14.3		341	74.5	12.2		−0.51, 0.08	−0.22
PCC-Z	50	−3.06	1.42		341	−2.51	1.51		−0.66, −0.07	−0.37 S
PVC	50	91.9	6.1		341	93.6	4.4		−0.66, −0.07	−0.36 S
PVC-Z	50	−3.24	1.97		341	−2.68	1.84		−0.60, 0.00	−0.30
II	50	88.8	10.2		341	92.1	7.8		−0.70, −0.11	−0.40 S
II-Z	50	−3.35	2.02		341	−2.65	2.10		−0.63, −0.04	−0.33 S
OII^f: % Lowered Intelligibility				34.0				14.1			0.002

Notes: OME = Otitis Media with Effusion; PE = Pressure Equalization; PCC-Z = Percentage of Consonants Correct-Z-score; PVC = Percentage of Vowels Correct; PVC-Z = Percentage of Vowels Correct-Z-score; II-Z = Intelligibility Index-Z-score; OII = Ordinal Intelligibility Index.

^a The right-most three columns include findings from between-group inferential statistical analyses of each variable. Statistically significant findings are bolded.

^b Effect Size: Small (S) >0.2; Medium (M) >0.5; Large (L) >0.8.

^c Fisher’s exact tests.

^d Shriberg and Lohmeier (2008).

^e Oral Composite Standard Score from Oral and Written Language Scales (OWLS; Carrow-Woolfolk, 1995).

^f Mabie and Shriberg (2017). Lowered intelligibility: <85%.

Figure 1. Persistence of Speech Motor Delay (SMD) in 14 participants treated for idiopathic Speech Delay (SD).

Table 6. Speech findings for 14 participants with concurrent Speech Delay and early Speech Motor Delay (SMD) treated for Speech Delay.

	Normalized SMD by 9 years of age (n = 11)				Persistent SMD (n = 3)				Between-group Comparisons
Variable	n	M	SD	%	n	M	SD	%	Confidence Interval	Effect Size	p-value^a
Demographic
Gender (male)	11			81.8	3			100.0			1.000
Age (yrs)	11	4.5	0.9		3	4.3	0.6		−1.06, 1.50	0.22
Speech^b
PCC	11	66.6	11.6		3	71.6	7.3		−1.71, 0.86	−0.43
PCC-Z	11	−3.30	1.15		3	−2.37	1.50		−2.02, 0.59	−0.72
PCCR	11	72.0	12.2		3	80.5	8.0		−1.99, 0.62	−0.69
PCCR-Z	11	−4.19	1.04		3	−2.97	1.89		−2.26, 0.39	−0.93
PVC	11	90.6	5.5		3	91.2	0.9		−1.39, 1.17	−0.11
PVC-Z	11	−3.58	1.67		3	−4.74	0.45		−0.60, 2.01	0.71
II	11	86.4	9.7		3	87.6	14.9		−1.38, 1.17	−0.10
II-Z	11	−3.55	2.12		3	−2.65	2.09		−1.68, 0.89	−0.40
OII^c: % Lowered Intelligibility				54.5				33.3			1.000

Notes: PCC = Percentage of Consonants Correct; PCC-Z = Percentage of Consonants Correct-Z-score; PCCR = Percentage of Consonants Correct-Revised; PCCR-Z = Percentage of Consonants Correct-Revised-Z-score; PVC = Percentage of Vowels Correct; PVC-Z = Percentage of Vowels Correct-Z-score; II = Intelligibility Index; II-Z – Intelligibility Index-Z-score; OII = Ordinal Intelligibility Index.

^a Fisher’s exact tests.

^b At first assessment.

^c Mabie and Shriberg (2017). Lowered intelligibility: <85%.

Table

The five Speech classifications and five Motor Speech classifications in the SDCS are each mutually exclusive. The five dysarthria subtype classifications are not mutually exclusive. That is, a speaker can meet percentile criteria for more than one of the five listed dysarthria subtype classifications (i.e., mixed dysarthria). See Supplement for the procedures and measures used to classify each motor speech disorder.
SDCS Classifications and Dysarthria Subtypes	Abbreviation	Age (yrs;mos) at Assessment	Description	References^a
Five Speech Classifications
Normal(ized) Speech Acquisition	NSA	3–80	Does not meet criteria for any of the four Speech Disorder classifications	2, 3, 4
Speech Errors	SE	6–8;11	Age-inappropriate speech sound distortions	3, 4
Persistent Speech Errors	PSE	9–80	Age-inappropriate speech sound distortions that persist past 9 years of age	4, 5
Speech Delay	SD	3–8;11	Age-inappropriate speech sound deletions and/or substitutions	3, 4
Persistent Speech Delay	PSD	9–80	Age-inappropriate speech sound deletions and/or substitutions that persist past 9 years of age	3, 4, 5
Five Motor Speech Classifications
No Motor Speech Disorder	No MSD	3–80	Does not meet criteria for any of the four Motor Speech Disorders classifications	2, 6, 8
Speech Motor Delay	SMD	3–80	Meets PSI criterion for SMD	2, 6, 8
Childhood Dysarthria	CD	3–80	Meets DI and DSI criteria for CD	2, 6, 8
Childhood Apraxia of Speech	CAS	3–80	Meets PM criterion for CAS	6, 7, 8
Childhood Dysarthria & Childhood Apraxia of Speech	CD & CAS	3–80	Meets SDCS criteria for CD & CAS	2, 6, 8
Five Dysarthria Subtypes
Ataxic		3–80	Cerebellar disorder	1, 2
Spastic		3–80	Upper motor neuron disorder	1, 2
Hyperkinetic		3–80	Basal ganglia disorder; increased movement	1, 2
Hypokinetic		3–80	Basal ganglia disorder; decreased movement	1, 2
Flaccid		3–80	Lower motor neuron disorder	1, 2

Notes: PSI = Precision-Stability Index; DI = Dysarthria Index; DSI = Dysarthria Subtype Index; PM = Pause Marker.

^a 1. Duffy (2013); 2. Mabie and Shriberg (2017); 3. Shriberg (1993); 4. Shriberg, Austin, Lewis, McSweeny, and Wilson (1997); 5. Shriberg et al. (2010a); 6. Shriberg and Mabie (2017); 7. Shriberg et al. (2017); 8. Tilkens et al. (2017).

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