Acoustic features of infant-directed speech to infants with hearing loss

Abstract

This study investigated the effects of hearing loss and hearing experience on the acoustic features of infant-directed speech (IDS) to infants with hearing loss (HL) compared to controls with normal hearing (NH) matched by either chronological or hearing age (Experiment 1) and across development in infants with HL as well as the relation between IDS features and infants' developing lexical abilities (Experiment 2). Both experiments included detailed acoustic analyses of mothers' productions of the three corner vowels /a, i, u/ and utterance-level pitch in IDS and in adult-directed speech (ADS). Experiment 1 demonstrated that IDS to infants with HL was acoustically more variable than IDS to hearing-age matched infants with NH. Experiment 2 yielded no changes in IDS features over development; however, the results did show a positive relationship between formant distances in mothers' speech and infants' concurrent receptive vocabulary size, as well as between vowel hyperarticulation and infants' expressive vocabulary. These findings suggest that despite their HL and thus diminished access to speech input, infants with HL are exposed to IDS with generally similar acoustic qualities as are infants with NH. However, some differences persist, indicating that infants with HL might receive less intelligible speech.

The Acoustic Features and Didactic Function of Foreigner Directed Speech: A literature Review.

“…Second, hyperarticulated vowel sounds elicit more mature neural responses and more successful sound discrimination in nine-month-old infants (Peter et al, 2016) and facilitate word recognition in 19-month-olds (Song et al, 2010). Critically, these relations are observed at the level of individual mother-infant dyads: mothers who exaggerate vowels to a greater extent in their IDS have infants with more advanced speech perception skills (Kalashnikova & Carreiras, 2021;Liu, Kuhl, & Tsao, 2003) as well as larger concurrent and future vocabularies (Hartman et al, 2017;Lovcevic et al, 2020).…”

Does Electrophysiological Maturation Shape Language Acquisition?

“…Although IDS is initially slow, caregivers accelerate their speech patterns across development; speech rate becomes comparable to adult-directed speech at around 2 years of infant age (Kondaurova et al, 2013; Lee et al, 2014; Narayan & McDermott, 2016; Raneri et al, 2020). In addition to adaptations of speech rate, caregivers have been found to prolong vowels in IDS (Englund & Behne, 2006; Hilton et al, 2022; Kondaurova & Bergeson, 2011; Lovcevic et al, 2020). The prolongation of vowels may ease phoneme-rate segmentation for the slow infant brain; moreover, it may help to make phonological contrasts more salient in time by slowing down the rate of phonological feature changes.…”

Language development in infants with hearing loss: Benefits of infant-directed speech

“…Mothers exaggerate pitch height and pitch range to a similar degree as they do to infants with NH matched by hearing experience but not to infants with NH matched by chronological age, suggesting that the nature of IDS is a response to infants' behaviour specifically related to their hearing experience, not behaviour that is a product of more general maturational growth or cognitive development (Bergeson et al, 2006;Miyamoto et al, 2005). As for infants with hearing aids, previous studies have demonstrated that pitch height and range are exaggerated in IDS to infants with HL to a similar degree as to infants with NH (Lovcevic et al, 2020;Traci, 1998).…”

“…Turning to the phonetics of IDS, while vowel hyperarticulation is evident in IDS to infants with HL, the evidence indicates that (i) vowel hyperarticulation in caregivers' IDS positively correlates with infants' spoken language outcomes (Dilley et al, 2020;Hartman et al, 2017;Kalashnikova & Burnham, 2018;Lovcevic et al, 2020), and (ii) the level of vowel hyperarticulation or vowel formant exaggeration may be modulated by known contrasts in hearing status (NH versus HL, Lam & Kitamura, 2010), or by the type of hearing prosthesis, hearing aids versus cochlear implants (Wieland et al, 2015). These vowel hyperarticulation findings raise two important questions.…”

“…In this regard, whereas detailed comparisons of tongue, lips and laryngeal movements in IDS and ADS show that vowel hyperarticulation does not have an explicitly articulatory linguistic basis (Kalashnikova et al, 2017), it does have a specifically linguistic outcome. This linguistic outcome is underlined by evidence that greater degrees of vowel hyperarticulation in maternal speech are linked to better linguistic outcomes for infants (Dilley et al, 2020;Hartman et al, 2017;Kalashnikova & Burnham, 2018;Kalashnikova & Carreiras, 2021;Lovcevic et al, 2020).…”