Impact of sentence length and phonetic complexity on intelligibility of 5-year-old children with cerebral palsy

Figures & data

Table I. Demographics of children with Cerebral Palsy (CP).

	Group SMI (n = 8)	Group NSMI (n = 8)	Group TD (n = 8)
Mean age (SD)	60.3 (3.0)	58.9 (3.7)	59.8 (3.5)
Male:female ratio	2:6	5:3	4:4
Type of CP
Diplegia	3	3	NA
Hemiplegia	2	4	NA
Quadriplegia	2	0	NA
Athetoid	1	0	NA
Ataxia	0	0	NA
Mixed	0	0	NA
Unknown	0	1	NA
GMFCS level
Level I	0	4	NA
Level II	2	4	NA
Level III	3	0	NA
Level IV	3	0	NA
Level V	0	0	NA

GMFCS, Gross Motor Classification System; SMI, speech motor impairment; NSMI, no speech motor impairment; TD, typically-developing.

Table II. Phonetic complexity characteristics of TOCS sentences.

	Total number of words across 10 sentences	Average phonetic complexity within sentence length	Phonetic complexity range within sentence length	Phonetic complexity SD within sentence length	Average phonetic complexity per word	Phonetic complexity range per word	Phonetic complexity SD per word
2-word sentences	20	10.58	7–19	2.64	5.16	2.25–8.00	1.24
3-word sentences	30	15.50	11–21	2.81	5.03	3.00–7.00	.98
4-word sentences	40	19.35	9–25	5.42	4.93	2.25–8.00	1.30
5-word sentences	50	26.22	20–35	4.80	5.14	2.25–7.00	1.01
6-word sentences	60	27.68	16–46	6.30	4.81	2.25–8.00	1.19
7-word sentences	70	33.55	24–43	5.71	4.87	2.25–8.00	.92

SD, standard deviation.

Figure 1. Mean intelligibility by utterance length and group.

Figure 2. Intelligibility by utterance length.

Table III. Pairwise t-tests examining within-group differences across complexity categories and utterance lengths.

Contrast	Mean difference	Standard deviation	T	p-value
TD Phonetic complexity quartiles Quartile 1 vs Quartile 2 Quartile 1 vs Quartile 3 Quartile 1 vs Quartile 4 Quartile 2 vs Quartile 3 Quartile 2 vs Quartile 4 Quartile 3 vs Quartile 4	1.63 3.96 .73 2.33 −.90 −3.24	5.96 4.77 4.24 7.52 5.92 5.36	1.73 5.25 1.08 1.96 −.96 −3.82	.091 .000** .283 .057 .339 .000**
Utterance length 2-word vs 3-word 2-word vs 4-word 2-word vs 5-word 2-word vs 6-word 2-word vs 7-word 3-word vs 4-word 3-word vs 5-word 3-word vs 6-word 3-word vs 7-word 4-word vs 5-word 4-word vs 6-word 4-word vs 7-word 5-word vs 6-word 5-word vs 7-word 6-word vs 7-word	.28 −.12 −1.24 −1.42 2.63 −.41 −1.52 −1.71 2.78 −1.11 −1.29 2.92 −.18 3.22 4.47	6.85 5.45 6.92 5.76 6.51 4.97 6.55 5.58 6.82 6.91 6.10 5.93 6.24 7.02 5.33	.26 −.14 −1.13 −1.55 2.39 −.53 −1.47 −1.93 2.41 −1.02 −1.34 2.91 −.18 2.71 4.96	.791 .886 .266 .128 .022 .602 .149 .061 .021 .316 .188 .006 .856 .010 .000*
NSMI Phonetic complexity quartiles Quartile 1 vs Quartile 2 Quartile 1 vs Quartile 3 Quartile 1 vs Quartile 4 Quartile 2 vs Quartile 3 Quartile 2 vs Quartile 4 Quartile 3 vs Quartile 4	1.16 6.56 .44 5.39 −.72 (6.12	7.73 7.74 6.27 9.15 7.46 8.84	.94 5.29 .44 3.68 −.60 −4.32	.353 .000** .662 .001** .550 .000**
Utterance length 2-word vs 3-word 2-word vs 4-word 2-word vs 5-word 2-word vs 6-word 2-word vs 7-word 3-word vs 4-word 3-word vs 5-word 3-word vs 6-word 3-word vs 7-word 4-word vs 5-word 4-word vs 6-word 4-word vs 7-word 5-word vs 6-word 5-word vs 7-word 6-word vs 7-word	.88 −1.35 1.00 .31 10.42 −2.24 .11 −.57 9.54 2.35 1.67 11.78 −.69 9.42 10.11	11.02 10.93 10.39 9.77 12.48 9.33 10.03 7.72 10.07 8.91 7.17 8.91 6.23 11.85 9.04	.50 −.77 .60 .20 5.22 −1.49 .07 −.46 5.91 1.59 1.45 8.25 −.69 4.96 6.98	.618 .444 .550 .842 .000* .142 .943 .645 .000* .120 .155 .000* .494 .000* .000*
SMI Phonetic complexity quartiles Quartile 1 vs Quartile 2 Quartile 1 vs Quartile 3 Quartile 1 vs Quartile 4 Quartile 2 vs Quartile 3 Quartile 2 vs Quartile 4 Quartile 3 vs Quartile 4	8.37 12.95 12.29 4.57 3.91 −.66	11.69 12.16 11.90 15.80 17.01 10.91	4.53 6.73 6.53 1.83 1.45 −.38	.000** .000** .000** .074 .153 .704
Utterance length 2-word vs 3-word 2-word vs 4-word 2-word vs 5-word 2-word vs 6-word 2-word vs 7-word 3-word vs 4-word 3-word vs 5-word 3-word vs 6-word 3-word vs 7-word 4-word vs 5-word 4-word vs 6-word 4-word vs 7-word 5-word vs 6-word 5-word vs 7-word 6-word vs 7-word	−4.63 5.63 10.43 9.78 15.67 10.25 15.06 14.41 21.86 4.80 4.15 9.79 −.64 2.01 4.44	11.56 10.95 15.46 15.14 17.58 13.58 19.15 18.11 15.77 12.01 13.32 15.69 11.69 16.04 11.71	−2.53 3.25 4.27 4.09 5.27 4.77 4.97 5.03 8.20 2.58 1.97 3.69 −.35 .75 2.24	.016 .002* .000* .000* .000* .000* .000* .000* .000* .016 .056 .001* .728 .462 .031

SMI, speech motor impairment; NSMI, no speech motor impairment; TD, typically-developing.

Criterion p-values for significance: **p ≤ .008; *p ≤ .003.

Figure 3. Mean intelligibility by complexity and group.

Figure 4. Intelligibility by complexity.

Table IV. Within-child multiple regression models examining the influence of phonetic complexity and sentence length on intelligibility. Overall sentence intelligibility across all stimulus sentences also presented for each child.

	B			Multiple R^2	Sentence intelligibility
Child	Constant	Phonetic complexity	Sentence length
1	97.05 (21.85)	−12.92 (3.50)***	.73 (2.70)	.24	34.9%
2	109.76 (17.45)	−4.22 (2.77)	−3.17 (1.83)	.08	73.5%
3	44.16 (14.83)	−2.14 (2.34)	−2.62 (1.75)	.06	21.0%
4	101.98 (20.98)	−4.56 (3.32)	−6.84 (2.18)**	.16	46.8%
5	102.58 (15.72)	−3.00 (2.49)	−6.30 (1.77)***	.21	60.5%
6	76.57 (19.34)	−2.93 (3.04)	−.10 (2.02)	.02	61.1%
7	97.96 (19.60)	−6.34 (3.09)*	−5.65 (2.02)**	.15	40.2%
8	55.92 (21.53)	.50 (3.38)	−5.12 (2.25)*	.09	34.0%

Observed p-values: *p ≤ .05; **p ≤ .01; ***p ≤ .001.