Patterns of speech sounds after surgery: investigating infants' phonological development following full cleft palate restorative surgery.

In the UK, 1 in every 700 babies are born with cleft lip and/or palate (NHS, 2020). Most infants with cleft palate (CP) receive full restorative surgery, but nevertheless will not necessarily go on to fully acquire target-like speech (Hardin-Jones, 2003, Kummer et al., 2012). Wren (2017) shows that as many as 50% of these infants never reach full speech proficiency, even after complete palate reconstruction. This research will aim to better understand why speech difficulties might persist in infants who have had successful cleft palate repair surgery through an analysis of early vocal production. The methodology integrates an established theory-the articulatory filter hypothesis (AFH)-presented by Vihman (2014:121) which proposes that infants notice words in input speech that match their production, and this, in turn, encourages a matching behaviour (feedback-loop) of phoneme-babble resemblances that encourage further vocal production. The AFH foregrounds the significance of production in early speech and that the phonological feedback-loop provides a key foundation for later linguistic advances. Research into the relationship between an infant's vocal production and their perception of has not yet explored how this crucial connection is established after cleft-palate repair. Insight into the AFH could indicate the importance of matching to the acoustic/phonetic properties of caregiver input for target-like production.
Research Questions:
How do the acoustic-phonetic properties of babble at 13-14 months (i.e., the articulatory and phonetic properties of babbled consonants) differ between typically developing infants and infants after cleft palate repair?
To what extent do CP infants respond to the sounds of caregiver speech in their own babble (following the framework set out in Laing and Bergelson, 2020)?
To what extent do patterns of babbling and caregiver input matching predict speech and language outcomes at 24 and 36 months? Is one a better predictor than the other?
The data will be from the Cleft Collective Speech and Language corpus (CC-SL), which includes English-speaking infants who have undergone full CP restoration (Wren et al. 2017). CC-SL contains data from over 600 children who were studied from birth to 5 years. Data was collected with a language environment analysis-or LENA-device (LENA Research Foundation, 2018), which captures caregiver speech in the infant's environment. The key variables include demographic, psychological, surgical, hearing, and speech/language data. A corpus of 48 TD infants from DePaolis et al. (2010) will serve as a valuable control sample; it includes a set of naturalistic recordings of mother-child interactions at 14 months, which will be tested against CP data for group differences. The CC-SL data on language outcomes (at 24 and 36 months) will be tested for individual differences across CP infants to assess whether they predict language outcomes.
The method will draw on a sample of 40 CP infants (post-surgery) and 40 TD infants (control group) to analyse phonological development and to determine whether the articulatory properties in babble can predict later speech outcomes in the CP infants. Descriptive statistics and corpus analysis approaches will serve to explore and analyse two main variables in CP vs. TD infants with a mixed methods approach: the acoustic-phonetic properties of infant babble produced in early vocalisations and the contingency between caregiver input and infant vocalisations.
Analyses will include the following stages:
-Acoustic phonetic analysis-using PRAAT (Boersma et al. 2019)-of consonant inventories at 13-14 months.
-Phonetic transcriptions-using ELAN (2020)-to investigate infant productions.
-Transcription of congruent/incongruent caregiver input preceding infant vocalisations, adapted from Laing and Bergelson (2020).
-Comparisons of consonant inventories at 13-14 months with speech and language outcomes at 24 and 36 months across CP