Prosodic complexity in the nonword repetition task: Language assessment of Serbian typically developing and children with specific language impairment

Abstract

The nonword repetition task (NRT), which consists of the presentation and instantaneous repetition of nonsense words, is widely used to gain insight into the phonological, lexical, and overall language development in typically developing (TD) children and vulnerable language populations. It is shown to be a promising assessment tool for specific language impairment (SLI) in numerous languages, because children with SLI consistently demonstrate poorer performance on this task compared to their TD peers. The aim of this study was to examine the ability of phonological repetition of TD and SLI children who are acquiring Serbian, by using the NRT constructed in accordance with the characteristics of the Serbian language. The study included 60 TD children aged 4 to 7 (n=15 per age group) and 42 children with SLI of the same ages (n=9-11 per age group). Forty eight prerecorded nonwords of varying prosodic complexity, with two systematically varied parameters of syllable structure (onset and coda) and two parameters of metrical structure (number of syllables and position of syllable stress), were presented in two randomized orders. Audio-recorded nonword repetitions were transcribed, and coded for accuracy and type of errors, which occurred on the word, syllable and phoneme level in the repetitions. The results show a significant effect of age (F(3,94)=18.64, p<0.001), and a significant effect of group (F(1,94)=155.1, p<0.001) on nonword repetition accuracy in TD and SLI Serbian children. There is no significant interaction between these two factors. Further analyses show a significant effect of the number of syllables on repetition accuracy (F(2,200)=275.3, p<0.001), as well as a significant interaction of group and the number of syllables (F(2,200)=5.335, p=0.006). The effect of the syllable structure is also significant (F(3,300)=122.9, p<0.001), as well as the interaction of group and syllable structure (F(3,300)=15.61, p<0.001). The analysis of errors reveals a significant effect of group (F(16,85)=12.22, p<0.001) for 12 of 16 types of errors on the word, syllable and phoneme level which occurred in repetitions. The largest differences between groups are shown for phoneme substitutions, consonant metathesis and onset consonant cluster reduction. It may be concluded that nonword repetition accuracy increases with age in both TD and SLI Serbian children, and that children with SLI are significantly and to a great extent less successful on the task at all tested ages compared to their TD peers. Children with SLI are significantly less successful at repeating nonwords of all examined prosodic structures, and they have more trouble with increasing prosodic complexity compared to TD children. Analysis of errors which occur in nonword repetitions indicates that SLI children generally make the same types but a significantly larger number of errors on the word, syllable, and phoneme level as TD children of the same ages. The nonwords used in this study are highly age and group discriminative and may be used for constructing a test, which would enable the assessment of phonological development of children acquiring Serbian, and with additional assessments in the clinical practice, enable the discrimination of SLI.