Survey Development of Compound Sentences and Mean Length of Utterance a Persian-speaking Child From 15 to 34 Months: a Longitudinal Case Report

 Acquisition skill in sentence producing is one of the criteria for speech development. By developing and increasing the age, we are witnessing the emergence of compound sentences in speech. Clinical treatments for language disorders in Iran are mostly based on the experiences of Speech Language Therapists or in accordance with English language norms. We need to examine how the length of utterance and compound sentences develop in Persian. The study aimed to report the development of compound sentences and Mean Length of Utterance (MLU) for a Persian-speaking child from 15 to 34 months.

In this longitudinal case report, based on Developmental-Descriptive model, MLU and emergence of simple compound sentences of a Persian speaking girl sampled and described from 15 to 34 months by daily scripting. R software version 4.0.2 was used for data analysis. Correlation of age with linguistic variables through Pearson correlation coefficient was evaluated.  Ethical Considerations: In this paper, the principles of publication ethics were considered.

 At the age of 21 months and 13 days, the child uttered her first simple two-word sentence, and at the age of 26 months and 29 days, she used a four-word compound sentence. With the emergence of compound sentences, the increase in the MLU has gained considerable speed. In a few days, we see the addition of a unit to the length of the sentence (word). There was a significant relationship between the MLU and age (r=‌0.925, P=‌0.001), Mean length of sentence and number of words in Persian speaking child (r=‌0.910, P=‌0.002) and total number of words and age (r=‌0.928, P<0.001). 

Although several longitudinal studies have been conducted on the development of MLU and number of words in other languages, similar studies are rare in Persian. It is important to conduct studies of this type in order to make cross-linguistic comparisons and to study the linguistic universality and language specificity. By increasing age, we see an increase in the number of words in a child's vocabulary, the emergence of compound sentences, and an increase MLU. At 27 to 28 months, there is a dramatic change in the development expressive language as the compound sentences appear. It seems that emergence of compound sentences in the language output, also plays a significant role in increasing the MLU and can be considered in clinical language assessments.