Relationship Between Parent Vowel Hyperarticulation in Infant-Directed Speech and Infant Phonetic Complexity on the Level of Conversational Turns.

Ulrika Marklund,Ellen Marklund,Lisa Gustavsson

doi:10.3389/fpsyg.2021.688242

Abstract

When speaking to infants, parents typically use infant-directed speech, a speech register that in several aspects differs from that directed to adults. Vowel hyperarticulation, that is, extreme articulation of vowels, is one characteristic sometimes found in infant-directed speech, and it has been suggested that there exists a relationship between how much vowel hyperarticulation parents use when speaking to their infant and infant language development. In this study, the relationship between parent vowel hyperarticulation and phonetic complexity of infant vocalizations is investigated. Previous research has shown that on the level of subject means, a positive correlational relationship exists. However, the previous findings do not provide information about the directionality of that relationship. In this study the relationship is investigated on a conversational turn level, which makes it possible to draw conclusions on whether the behavior of the infant is impacting the parent, the behavior of the parent is impacting the infant, or both. Parent vowel hyperarticulation was quantified using the vhh-index, a measure that allows vowel hyperarticulation to be estimated for individual vowel tokens. Phonetic complexity of infant vocalizations was calculated using the Word Complexity Measure for Swedish. Findings were unexpected in that a negative relationship was found between parent vowel hyperarticulation and phonetic complexity of the immediately following infant vocalization. Directionality was suggested by the fact that no such relationship was found between infant phonetic complexity and vowel hyperarticulation of the immediately following parent utterance. A potential explanation for these results is that high degrees of vowel hyperarticulation either provide, or co-occur with, large amounts of phonetic and/or linguistic information, which may occupy processing resources to an extent that affects production of the next vocalization.

Highlights

This study investigates the relationship between parents’ infantdirected speech (IDS) and the developing speech production of the infant
The average vhh-index for parent utterances was calculated on the remaining tokens within each utterance, and as such no utterances were considered outliers
The results show a negative relationship between parent vowel hyperarticulation (VH) in IDS to their 12-month-old infants and the phonetic complexity (PC) of infant vocalizations on a turn level; the more hyperarticulated a parent utterance is, in terms of mean and max vhh-index weighted for vowel duration, the less phonetically complex the following infant vocalization is, in terms of Word Complexity Measure for Swedish (WCM-SE) score

Summary

Introduction

This study investigates the relationship between parents’ infantdirected speech (IDS) and the developing speech production of the infant. From a phonetic point of view, it is to be expected that the degree of VH in parents’ speech varies with the perceptual requirements of the child (Lindblom, 1990; Buz et al, 2016; Marklund and Gustavsson, 2020), whether that be different stages of language development or dynamic in-the-moment fluctuations in focus and attention This means that VH is a characteristic of IDS which is likely highly susceptible to contextual influence, and that it may well be the case that the varying degrees of VH in parent IDS is an adaptive response to perceived cues from the infant. This study aims to determine whether such a relationship can be found on the level of individual conversational turns, and if so, if any directionality can be established

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Conclusion