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Childhood apraxia of speech (CAS) is a paediatric motor speech disorder. We investigated the lexical tone perception and production abilities of children with CAS and the relationships between the two. Three children with CAS, aged between 3;7 and 5;8, were given the Cantonese Tone Identification Test (CANTIT) and the Hong Kong Cantonese Articulation Test (HKCAT) for assessment of tone perception and production, respectively. Accuracy and error patterns were investigated based on their performance on the two tests. Correlation analysis was performed on children's perception and production scores. Two children scored at the lowest rank on the CANTIT, while one child obtained a Z score of 0. All children scored three standard deviations below the mean on the HKCAT. No statistical differences were found among the six tones with respect to perception accuracy, H (5) = 3.731, p = 0.589. Error analysis showed that children with CAS demonstrated more confusion on perceiving tones compared with TD peers. There were no main effects for task ( F (1,2) = 0.040, p = 0.859) or tone (F(5,10 = 0.997, p = 0.467); nor were there task or tone interaction effects on perception versus production accuracy ( F (5,10) = 1.772, p = 0.206). Tone perception and production accuracy were not significantly correlated ( r 2  = 0.181, p = 0.078). Tone perception deficits were evident in two out of three children with CAS, while all children had lexical tone production difficulties. In this small sample, tone production was more universally affected than tone perception.

Introduction Pitch variation, which refers to one's ability to vary fundamental frequency (F0) within or between syllables when speaking, has not been investigated in children with childhood apraxia of speech (CAS). However, pitch variation plays an important role in tone languages, as varying F0 patterns communicate different lexical meanings. This study investigated pitch variation abilities in individuals with CAS via the tone-sequencing tasks (TSTs), focusing on task performance and the effects of syllable structure, lexical status, and tones. Method Three Cantonese-speaking children with CAS (aged 3;7-5;8 [years;months]) and six children without CAS participated in the study. Children without CAS were divided into two control groups, comprising those with speech and/or language impairment or typical development. TSTs consisted of 56 sets of five repetitions of stimuli. The stimuli varied in syllable structure, lexical status, and tones. Percentage of tones correct (PTC), consistency scores, F0 values, and acoustic repetition duration were measured. Results The CAS group performed more poorly than the control groups on the TST with respect to tone accuracy, consistency, and repetition duration. No interaction effects between group and syllable structure or group and lexical status were found. No significant difference was found on F0 values across time between Tone 1 and Tone 2 syllables in the CAS group. However, interaction effects between group and time points of F0 values on Tone 2 syllables were found. Discussion The results suggest that children with CAS have difficulty with pitch variation, which was revealed on the TST with respect to tone accuracy, consistency, and repetition duration. Moreover, children with CAS have difficulty in varying F0 values to produce high-rising tones and tend to use high-level tones to substitute. Clinically, the TST may be useful to assist in the diagnosis of CAS. Isolated vowel stimuli may be useful to test young children or children with severe impairment. Future investigations and development of a normed tool for children with CAS are suggested.