Mean length of utterance in Czech toddlers (Matiasovitsová et al., 2024)
Purpose: We examined the properties of mean length of utterance (MLU) in Czech, a morphologically complex Slavic language. We compared the scores of MLU calculated in different units and based on different sample lengths and assessed its validity against another transcript and test-based measures.
Method: One hundred nine children were recorded during free-play at 2;6 and 3;11 (years;months). We compared MLU in syllables, morphemes, and words (MLUw) in transcripts of different lengths (50, 75, 100, and all available utterances). For evaluating the validity of MLU, we also calculated Index of Productive Syntax (IPSyn) and number of different words (NDW) and used results of receptive vocabulary and grammar comprehension tests.
Results: The different MLU measures based on different sample lengths correlated closely with MLU in transcripts of all utterances (all rs > .87). We found mostly strong correlations between MLU, IPSyn, and NDW at both time points and weak or moderate correlations between MLU and grammar and vocabulary. Regression models showed the significant unique effect of MLUw at 2;6 for MLUw (β = .29) and grammar (β = .33) at 3;11 and vocabulary (β = .27) at 3;7.
Conclusion: MLUw based on all utterances was confirmed as a valid measure of early language skills in Czech, as it is stable in time and shows concurrent and predictive relations with other transcript-based and test-based measures.
Supplemental Material S1. Correlations between MLU measured in words, morphemes and syllables based on different number of utterances (all, 50, 75 or 100) in transcripts with the minimum of 100 utterances.
Supplemental Material S2. Correlations between transcript-based and test-based measures (MLUw based on 50 or 75 utterances).
Supplemental Material S3. Correlations between MLUw based on 50 or 75 utterances at Time 1 (1) and test-based measures at Time 2 (2).
Supplemental Material S4. Regression model showing effects of MLU in syllables based on all utterances and the grammar and vocabulary test at Time 1 (1) on the MLU in syllables, grammar and vocabulary test at Time 2 (2).
Supplemental Material S5. Regression model showing effects of MLU in morphemes based on all utterances and the grammar and vocabulary test at Time 1 (1) on the MLU in morphemes, grammar and vocabulary test at Time 2 (2).
Supplemental Material S6. Regression model showing effects of MLU in words based on 50 utterances and the grammar and vocabulary test at Time 1 (1) on the MLU in words, grammar and vocabulary test at Time 2 (2).
Supplemental Material S7. Regression model showing effects of MLU in words based on 75 utterances and the grammar and vocabulary test at Time 1 (1) on the MLU in words, grammar and vocabulary test at Time 2 (2).
Matiasovitsová, K., Čechová, P., Sláma, J., Homolková, K., Smolík, F. (2024). Mean length of utterance in Czech toddlers: Validity estimates and comparison of words, morphemes, and syllables. Journal of Speech, Language, and Hearing Research, 67(3), 837–852. https://doi.org/10.1044/2023_JSLHR-23-00251
