Investigating Mean Length of Utterance (MLU) in Monolingual Persian Speaking Children with Autism Spectrum Disorder (ASD)

Background: Mean length of utterance (MLU) is one of the most important measures in estimating language acquisition in children. The study of how language develops in these patients can be useful in providing effective treatment strategies. This study aims to investigate the developmental process of MLU in children with ASD and compare them with normal children. Methods: This study is a descriptive, cross-sectional-quantitative one. The statistical society is all 3-6 years of children with ASD in Tehran, and the sample has been selected via cluster sampling among welfare organizations in region 6 (Mantaghe 6). The participants included 10 monolingual Persian children with ASD aged 3-6. In this research, the spoken utterances of children were recorded and transcribed in 30 minutes of free play sessions. The control group included 10 monolingual Persian children aged 2-5, with no previous linguistic and psychological disorders. Two groups were matched based on nonverbal IQ and gender. Results: Based on the findings, the mean and standard deviation of MLU in autistic children were 2.5 and 1.24, respectively and the mean and standard deviation of MLU in normal children were 3.74 and 1.03, respectively. The results of T-test analysis showed a statistically significant difference between two groups with regard to the MLU (t (18)=-2.41, Pvalue=0.02). The results also indicated a statistically significant correlation between MLU and age in children with ASD (Pvalue=0.01, r=0.95) and in normal children (Pvalue=0.000, r=0.95). Conclusions: The study showed that after controlling for vocabulary knowledge, non-verbal IQ and talkativeness, MLU was significantly lower in children with ASD than in normal children. The results also showed that MLU increases with increase of age in both groups.