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Hidden behind a smile: acquisition and societal perception of speech sounds in children with cleft lip and palate.

Cleft lip and palate (CLP) is a birth defect causing the upper lip, hard palate and/or the soft palate (the velum) not to fuse together correctly in the womb. It is the most common facial birth defect in the UK affecting 1 in 700 infants (NHS, 2019). Though there is much research into the effects that this has on an infant’s ability to breastfeed, there is very little on the effects it has on a child’s speech sound acquisition. Particularly, how speech and language therapy (SLT) supports a child in reaching a similar intelligibility as their non-CLP peers. It is suggested that a child with CLP that has undergone SLT intervention should have “good quality, intelligible (understandable) speech by age 5-6” (CLAPA, 2021). I explore the validity of this claim utilising pre-existing knowledge on phoneme acquisition, as well as gathering the general public’s view on CLP through a perception study. The sounds I base this research on are fricatives, plosives and affricates. These are the sounds that are predominantly affected by CLP as they require a degree of closure in the oral cavity in order to be produced which is often lost through the air escaping through the palate and out from the nasal cavity.
The data for this study was collected from a questionnaire distributed via social media. It asked that participants have no known hearing loss and that they be either L1 or fluent L2 speakers of English. The questionnaire asked participants to listen to single word audios of multiple Scottish children and offer a transcription, a 1-5 intelligibility rating and asked whether they believed the child to have CLP.
Using a basis of a control group, I used prior research by Flipsen (2006) which gave a percentage for the expected intelligibility of typically developing children at age 4 (which is the beginning of the age range of the child speakers in the audios presented). I then compared this to a study by Gordon-Brannan & Hodson (2000) which suggested a percentage intelligibility which, if a child fell below this, indicated the presence of a speech development disorder. Overall, I discovered that the idea that a child will have developed good quality and intelligible speech by the age of 5-6 years after SLT intervention is not entirely accurate as the CLP childrens’ average intelligibility still indicated a lag in speech development.
From a social perspective, I also discovered that much of the general public has a relatively poor understanding of cleft lip and palate. This suggests that further education is required. Though CLP is a physical defect which can be seen to the eye and so treatment often begins quickly, these findings also suggest that there is little understanding of speech development disorders as a whole. If this is the case, adults may not be able to identify when a child requires SLT intervention in cases of less prominent speech issues.

References
CLAPA. (2021). Speech. How is it Treated? https://www.clapa.com/what-is-cleft-lip- palate/how-is-it-treated/  
Flipsen, P. (2006). Measuring the intelligibility of conversational speech in children. Clinical Linguistics & Phonetics 20(4), 303-312. National Library of Medicine. 
Gordon-Brannan, M., & Hodson, B. (2000). Intelligibility/Severity Measurements of Prekindergarten Children's Speech. American Journal of Speech-Language Pathology, 9, 141-150.
NHS. (2019, August 13). Cleft lip and palate. Cleft lip and palate. https://www.nhs.uk/conditions/cleft-lip-and-palate/