Vowels Development in Babbling of typically developing 6-to-12-month old Persian-learning Infants

Objectives: Pre-linguistic vocalizations including early consonants, vowels, and their combinations into syllables are considered as important predictors of the speech and language development. The purpose of this study was to examine vowel development in babblings of normally developing Persian-learning infants. Methods: Eight typically developing 6-8-month-old Persian-learning infants (3 boys and 5 girls) participated in this 4-month longitudinal descriptive-analytic study. A weekly 30-60-minute audio- and video-recording was obtained at home from the comfort state vocalizations of infants and the mother-child interactions. A total of 74:02:03hours of vocalizations were phonetically transcribed. Seven vowels comprising /i/,/e/,/a/,/u/,/o/,/alpha/, and /(sic)/ were identified in the babblings. The inter-rater reliability was obtained for 20% of vocalizations. The data were analyzed by repeated measures ANOVA and Pearson's correlation coefficient using SPSS software version 20. Results: The results showed that two vowels /a/ (46.04) and /e/ (23.60) were produced with the highest mean frequency of occurrence, respectively. Regarding front/back dimension, the front vowels were the most prominent ones (71.87); in terms of height, low (46.78) and mid (32.45) vowels occurred maximally. A good inter-rater reliability was obtained (0.99, P<.01). Conclusion: The increased frequency of occurrence of the low and mid front vowels in the current study was consistent with previous studies on the emergence of vowels in pre-linguistic vocalization in other languages.