The origins of babytalk: smiling, teaching or social convergence?

Abstract

When addressing their young infants, parents systematically modify their speech. Such infant-directed speech (IDS) contains exaggerated vowel formants, which have been proposed to foster language development via articulation of more distinct speech sounds. Here, this assumption is rigorously tested using both acoustic and, for the first time, fine-grained articulatory measures. Mothers were recorded speaking to their infant and to another adult, and measures were taken of their acoustic vowel space, their tongue and lip movements and the length of their vocal tract. Results showed that infant- but not adult-directed speech contains acoustically exaggerated vowels, and these are not the product of adjustments to tongue or to lip movements. Rather, they are the product of a shortened vocal tract due to a raised larynx, which can be ascribed to speakers' unconscious effort to appear smaller and more non-threatening to the young infant. This adjustment in IDS may be a vestige of early mother–infant interactions, which had as its primary purpose the transmission of non-aggressiveness and/or a primitive manifestation of pre-linguistic vocal social convergence of the mother to her infant. With the advent of human language, this vestige then acquired a secondary purpose—facilitating language acquisition via the serendipitously exaggerated vowels.

Infant‐directed speech to infants at risk for dyslexia: A novel cross‐dyad design

“…In order to measure vowel hyperarticulation, instances of the three corner vowels /i, u, and a/ were required. Following previous IDS studies (Burnham et al, ; Kalashnikova & Burnham, ; Kalashnikova et al, , ; Lam & Kitamura, ), mothers were given a toy sheep, a baby shoe, and a toy shark (note that “r” is non‐rhotic in Australian English), and a set of pictures that depicted these three items in different situations (e.g., shoe, sheep, and shark superimposed on a beach scene) to aid conversation using those three words. The length of the sessions ranged from 5 to 10 min.…”

“…For instance, it has been proposed that these IDS components are the product of parental intentions to express emotion and regulate infant behavior (Benders, 2013;Singh, Morgan, & Best, 2002;Trainor, Austin, & Desjardins, 2000). Most recently, it has been argued that these components are the product of parents' unconscious intention to sound more like their infant (Englund & Behne, 2005), or similarly, parents' unconscious intention to appear smaller and less threatening (Kalashnikova, Carignan, & Burnham, 2017).…”

Perception of audiovisual infant directed speech

“…Findings were verified in analyses of formant frequencies, revealing F 1 to be higher during IDS than ADS for the vowels studied, and F 2 to be higher in IDS than ADS for the low vowels /ae/ and /a/, but not for /i/ (Green et al, 2010). An alternative account for different formant frequencies in IDS has recently been presented, based on eight mothers' vocal tract length estimated by formant frequency values in IDS speech (Kalashnikova, Carignan & Burnham, 2017). The authors claim that IDS vowel acoustics is a product of laryngeal raising, resulting from social convergence.…”

Lexical Learning May Contribute to Phonetic Learning in Infants: A Corpus Analysis of Maternal Spanish

“…Child-directed speech evolves to some degree as infants grow into young children, so it is possible that results with a different corpus would be different. There is no consensus about whether speech-sound categories are more readily identifiable in infant-directed speech or adult-directed speech, or in different varieties of infant-directed speech (e.g., Kalashnikova et al, 2017;Miyazawa et al, 2017, Stern, Spieker, Barnett, & MacKain, 1983. This issue merits further consideration with additional corpora.…”

“…Thus, in our view, there is room for doubt that infant-directed speech presents infants with distinct distributions of speech sounds that map onto phonetic categories (see also Burnham, Wieland et al, 2015;Martin et al, 2015;Narayan, 2013;Sundberg & Lacerda, 1999). Indeed, whether infant-directed speech should be considered a better teaching signal than adult-directed speech has been questioned, with much of the current evidence showing that infant-directed vowel categories are not particularly separated in phonetic space (e.g., Martin et al, 2015;McMurray, Kovack-Lesh, Goodwin, & McEchron, 2013;Miyazawa, Shinya, Martin, Kikuchi, & Mazuka, 2017) even if the average formant values of the point vowels [i,a,u] are more spread out (e.g., Kalashnikova, Carignan, & Burnham, 2017).…”