Relationship between mean length of utterance and vocabulary in children with typical language development

Mean Length of Utterance in Czech Toddlers: Validity Estimates and Comparison of Words, Morphemes, and Syllables

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

https://doi.org/10.23641/asha.25215203.

How infants' utterances grow: A probabilistic account of early language development

Why are children's first utterances short and ungrammatical, with some obvious constructions missing? What determines the lengthening of children's early utterances over time? The literature is replete with references to a one-word, a two-word, and a later multiword stage in language development, but with little empirical evidence, and with little account for how and why utterances grow. To address these questions, we analyze speech samples from 25 children between the ages of 14 and 43 months; we construct distributions of their utterances of lengths one to five by age. Our novel findings are that multiword utterances of different lengths appear early in acquisition and increase together until they reach relatively stable proportions similar to those found in parents' input. To explain such patterns, we develop a probabilistic computational model, VIRTUAL, that posits an interaction between a) varying, increasing resources from various developmental domains and b) target utterance lengths mirroring the input. VIRTUAL successfully accounts for most of the empirical patterns, suggesting a probabilistic and dynamic process that is nonetheless compatible with apparent distinct milestones in development. We provide a new, systematic way of showing how developmental cascade theories could work in language development. Our findings and model also suggest insights into syntactic, semantic, and cognitive development.

Development of narratives in Tamil-speaking preschool children: A task comparison study

‘Narrative’ can be simply defined as a spoken or written account of connected events or experiences. The present study records the development of microstructure elements of narratives in 200 typically developing Tamil-speaking children aged between three years and six years and eleven months. It then compares their narrative productivity across two elicitation contexts: story retelling (SR) and story generation (SG). The samples thus obtained are analyzed for three narrative microstructure parameters, namely total number of words (TNW) in the narrative, mean length of utterances (MLU) and the number of utterances. The results reveal an increasing trend in all three microstructure parameters across both contexts. All three parameters are found to be quantitatively high in SR than in SG. Variation in the performance in these narrative tasks has been explained with behavioural observations from literature, cognitive architecture and a working memory model. It was found that gender differences do not follow a uniform pattern across age groups and elicitation contexts. Since the study has generated normative data for microstructure parameters of narratives, the observations can be used to analyze language deviance and help plan the narrative intervention protocol for language therapy.