Infant-Directed Speech Does Not Always Involve Exaggerated Vowel Distinctions: Evidence From Danish

Abstract

The phonological peculiarities of spoken Danish have been argued to reduce the salience of cues that allow infant listeners to extract linguistic information from the speech stream. To assess whether caregivers adjust their infant-directed speech to accommodate these processing challenges, this study compares the acoustic properties of 26 Danish caregivers’ spontaneous speech when interacting with their 11-24-month-old infants (i.e., infant-directed speech, IDS) and when interacting with an adult experimenter (i.e., adult-directed speech, ADS). We compare the two speech styles on both prosodic and vocalic dimensions by extracting 25,577 prosodic measures from utterances as well as 9255 vocalic measures from manually annotated vowel tokens. We construct Bayesian multi-level models of each acoustic feature and critically incorporate statistical information from prior studies into our analyses. The results indicate that Danish IDS conforms to general cross-linguistic patterns in its prosodic properties, with a higher overall pitch, a greater degree of pitch variability and a slower articulation rate. Crucially, though, the acoustic properties of Danish vowels contradict cross-linguistic tendencies: Danish caregivers tend to produce IDS with a reduced or similar vowel space area, higher within-vowel variability, and a lower degree of distinctiveness between vowel categories. We argue that these results beg for future research to pursue theory-driven comparisons of the acoustic expression of IDS across a wide intersection of languages with distinct phonological systems.

Vowel-hyperarticulation in Infant-directed Speech: A Multi-method Meta-analysis

“…As all the study methods were comparable, these varied findings suggest that vowel hyperarticulation in IDS might not be a universal phenomenon. Further studies employing different methods than Kuhl et al (1997) (e.g., inclusion of more than three vowels, inclusion of vowels other than corner vowels, IDS recorded during reading sessions, Benders et al, 2013;Cox et al, 2022;Englund & Behne, 2006) also provide conflicting findings regarding the presence of vowel hyperarticulation in IDS.…”

Mothers’ and fathers’ infant-directed speech have similar acoustic properties, but these are not associated with direct or indirect measures of word comprehension in 8–month-old infants

“…A growing body of research, using advanced acoustic analyses, provides evidence against the hypothesis of enhanced clarity of IDS, implying that the traditionally reported vowel space area may be a too crude proxy for the 'clear speech' claim. Vowel categories in IDS appear to be less distinctive, as compared to ADS: they are separated by smaller acoustic distances (Cristia & Seidl, 2014;Cox et al, 2022b), and spectral differences between them are reduced (Martin et al, 2015). In addition, vowels in IDS appear to be more variable, as revealed by larger within-category variability (Cristia & Seidl, 2014;Englund, 2018;McMurray et al, 2013;Miyazawa et al, 2017;Rosslund et al, 2022) and larger change in the spectral dynamics over the vowel duration (Miyazawa et al, 2017).…”

“…Further, our results revealed that parents expanded their vowel space in IDS, both when measuring the full vowel space, and with the three most extreme corner vowels in Norwegian (/i/-/ae/-/u/), and that their vowel categories were more variable and less distinct in IDS than ADS. Hence, while IDS certainly features more exaggerated prosody and might function as a 'perceptual hook', vowel categories were more variable when compared to ADS (see also Cristia & Seidl, 2014;Cox et al, 2022b;Miyazawa et al, 2017;Rosslund et al, 2022), and hence may not provide a cleaner acoustic input to the child.…”

Language‐Specific Constraints on Conversation: Evidence from Danish and Norwegian

“…However, the extent to which they vary and adapt to different contextual constraints (e.g., a casual chat vs. reaching a joint decision at work vs. helping a child in developing their language) is only now starting to be systematically investigated (Colman & Healey, 2011; Cox et al., 2022a, 2022b; Dideriksen, Christiansen, Tylén, Dingemanse, & Fusaroli, 2023; Healey, Purver, & Howes, 2014). Similarly, while it is acknowledged that cross‐linguistic and cross‐cultural variations play a crucial role in human behavior and cognition (Christiansen, Contreras Kallens, & Trecca, 2022; Cox et al., 2022a, 2022b; Henrich, Heine, & Norenzayan, 2010; Trecca, Tylén, Højen, & Christiansen, 2021), very little is known about how conversational dynamics systematically vary and adapt to diverse languages and cultures.…”

“…The dynamics of mutual understanding are an integral part of how we understand human cognition in context (e.g., Dale, Fusaroli, Duran, & Richardson, 2013; Fusaroli, Demuru, & Borghi, 2012; Schilbach et al., 2013), and are becoming crucial components in the development of human–computer interfaces (Loth, Jettka, Giuliani, & De Ruiter, 2015; Sugiyama, Meguro, Yoshikawa, & Yamato, 2018), and clinical assessments of social functioning (Dwyer, David, McCarthy, McKenna, & Peters, 2019; Hopkins, Yuill, & Keller, 2016; Schilbach et al., 2013). However, the extent to which they vary and adapt to different contextual constraints (e.g., a casual chat vs. reaching a joint decision at work vs. helping a child in developing their language) is only now starting to be systematically investigated (Colman & Healey, 2011; Cox et al., 2022a, 2022b; Dideriksen, Christiansen, Tylén, Dingemanse, & Fusaroli, 2023; Healey, Purver, & Howes, 2014). Similarly, while it is acknowledged that cross‐linguistic and cross‐cultural variations play a crucial role in human behavior and cognition (Christiansen, Contreras Kallens, & Trecca, 2022; Cox et al., 2022a, 2022b; Henrich, Heine, & Norenzayan, 2010; Trecca, Tylén, Højen, & Christiansen, 2021), very little is known about how conversational dynamics systematically vary and adapt to diverse languages and cultures.…”