Parents’ hyper-pitch and low vowel category variability in infant-directed speech are associated with 18-month-old toddlers’ expressive vocabulary

The present study examines the acoustic properties of infant-directed speech (IDS) as compared to adult-directed speech (ADS) in Norwegian parents of 18-month-old toddlers, and whether these properties relate to toddlers’ expressive vocabulary size. Twenty-one parent-toddler dyads from Tromsø, Northern Norway participated in the study. Parents (16 mothers, 5 fathers), speaking a Northern Norwegian dialect, were recorded in the lab reading a storybook to their toddler (IDS register), and to an experimenter (ADS register). The storybook was designed for the purpose of the study, ensuring identical linguistic contexts across speakers and registers, and multiple representations of each of the nine Norwegian long vowels. We examined both traditionally reported measures of IDS: pitch, pitch range, vowel duration and vowel space expansion, but also novel measures: vowel category variability and vowel category distinctiveness. Our results showed that Norwegian IDS, as compared to ADS, had similar characteristics as in previously reported languages: higher pitch, wider pitch range, longer vowel duration, and expanded vowel space area; in addition, it had more variable vowel categories. Further, parents’ hyper-pitch, that is, the within-parent increase in pitch in IDS as compared to ADS, and lower vowel category variability in IDS itself, were related to toddlers' vocabulary. Our results point towards potentially facilitating roles of increase in parents’ pitch when talking to their toddlers and of consistency in vowel production in early word learning

Robustness of Word Comprehension in 18-20-month-old Norwegian Toddlers

Infants use a range of cues to map words to the world around them, such as shape, familiarity, frequency or context of use, and when these cues are not available, they typically fail to disambiguate between competing referents. This suggests that representations for specific words might not yet be firmly grounded in their lexicon, and certain conditions need to be met to reveal comprehension. This impreciseness of early word representations sets challenges for the validity of parental reports of children’s word comprehension, such as the MacArthur Bates Communicative Development Inventories (CDI), a widely used measure in both language research and clinical practice. The current pre-registered study set out to explore both the robustness of early word comprehension and the validity of such parental reports. Sixty 18-20-month-old Norwegian toddlers performed a touch-based forced-choice word recognition task, in which they were prompted to identify the labelled target out of two displayed items on a touchscreen tablet. In each trial, the distractor item was either semantically related (e.g., dog-cat) or unrelated (e.g., dog-airplane) to the target, and we compared toddlers’ accuracy in identifying the target to their parents’ reports of comprehension on the CDI. The results show that toddlers are marginally more accurate in the semantically unrelated condition, are biased towards animate items, and that parents are relatively reliable, but tend to underestimate their children’s word comprehension. We also present, to the best of our knowledge, the first evidence of the efficacy of remote data collection of word recognition with a developmental sample, through comparable results from both in-lab and online administration of our recognition task

Friends of the babylab: A stimuli picture book

"Friends of the babylab" is a child-friendly picture book created for research purposes. The book consists of five independent illustrations/short stories. The stories revolve around animals, and numerous familiar objects are found in each illustration. The book was originally created to elicit infant-directed speech from parents (see https://osf.io/hxb4v/), and illustrations were paired with a written narrative. However, the illustrations can serve various purposes depending on study. The full book (ready to print!), individual illustrations, and original version with Norwegian text can all be found under ‘Files’. The book is shared under a CC-BY-NC 4.0 license, meaning it can be freely shared and used for non-commercial purposes, with credit to the original creators. Please give us a nod by citing any use as: Rosslund, A., Kartushina, N., & Tønder, J. (2022, October 25). Friends of the babylab: A stimuli picture book. https://doi.org/10.17605/OSF.IO/SMZJ2

Association between shared book reading, daily screen time and infants’ vocabulary size

In the current pre-registered study, we examined the associations between shared book reading, daily screen time, and vocabulary size in 1,442 12- and 24-month-old Norwegian infants. Our results demonstrate a positive association between shared reading and vocabulary in both age groups, and a negative association between screen time and vocabulary in 24-month-olds. Exploratory analyses revealed that the positive relationship between shared reading and expressive vocabulary in 12-month-olds was stronger in lower SES groups, suggesting that shared reading may act as a compensatory mechanism attenuating potentially impoverished learning environment and parent-infant interactions in low-SES families

Toddlers raised in multi-dialectal families learn words better in accented speech than those raised in monodialectal families

Abstract Multi-accent environments offer rich but inconsistent language input, as words are produced differently across accents. The current study examined, in two experiments, whether multi-accent variability affects infants’ ability to learn words and whether toddlers’ prior experience with accents modulates learning. In Experiment 1, two-and-a-half-year-old Norwegian toddlers were exposed, in their kindergarten, twice per day for one week, to a child-friendly audiovisual tablet-based e-book containing four novel pseudowords. Half of the toddlers heard the story in three Norwegian accents, whereas the other half heard it in one Norwegian accent. The results revealed no differences between conditions, suggesting that multi-accent variability did not hinder toddlers’ word learning. In experiment 2, two-and-a-half-year-old Norwegian toddlers were exposed, in their homes, for one week, to the e-book featuring three Norwegian accents. The results revealed overall better learning in toddlers raised in bi-dialectal households, as compared to mono-dialectal peers – suggesting that accent exposure benefits learning in multi-accent environments

Properties of infant-directed speech and its relation to expressive vocabulary in 18-month-old toddlers in Northern Norway

The current study will examine the acoustic properties of infant-directed speech (IDS) to 18-month-old Norwegian toddlers, and will assess whether these properties, or the (articulatory) effort that parents make when speaking IDS as compared to adult-directed speech (ADS), i.e., the acoustic differences between the two registers, are related to toddlers' expressive vocabulary size. The data was collected in Tromsø, Norway, from parents speaking a Northern Norwegian dialect, and parental input was recorded in the lab, from the child's main caregiver that could be either child's mother or father. To avoid effects of linguistic variables, e.g., consonantal context (known to influence vowels, see Steinlen & Bohn, 1999; Steinlen, 2005), between the two registers, both IDS and ADS were elicited via a storybook reading task

Properties of infant-directed speech and its relation to direct and indirect measures of word comprehension in 8-month-old Norwegian infants

The current study will examine the acoustic properties of infant-directed speech (IDS) to 8-month-old Norwegian infants, and will assess whether these properties, or the (articulatory) adaptation that parents make when speaking IDS as compared to adult-directed speech (ADS), i.e., the acoustic differences between the two registers, are related to infants' emerging language, as indexed by both parent report (CDI) and an eye-tracking experiment (IPL) of word comprehension. In a previous study with 18-month-old toddlers in Northern Norway, Rosslund et al. (2021) found that IDS is characterized by increased pitch, pitch range and vowel duration, as well as vowel space expansion, yet, more variable vowel categories. It was also found that parents' hyper-pitch, and low vowel category variability in IDS, was associated with expressive vocabulary size. The current study aims to assess the same properties of Norwegian IDS as in the previous study (Rosslund et al., 2021), directed this time to 8-month-old infants growing up in Oslo and exposed to Eastern Norwegian dialect, and whether there are associations between the above-mentioned features of parents' speech (supplemented with additional measures, see section 'Design Plan') and infants' language development (e.g., Hartman et al., 2017; Kalashnikova & Burnham, 2018; Rosslund et al., 2021), also when indexed by direct measures. The data was collected in a babylab in Oslo, Norway, and parents' input was recorded from the child's main caregiver who could be either child's mother or father. As compared to previous studies in Norwegian, the current sample had a balanced representation of both fathers and mothers. To avoid effects of linguistic variables, e.g., consonant context (known to influence vowels, see Steinlen & Bohn, 1999; Steinlen, 2005) between the two registers, both IDS and ADS were elicited via a storybook reading task. This pre-registration largely follows that of Rosslund et al., 2021 (https://osf.io/7st6w/) with 18-month-old toddlers, hence the study design and the analysis pipeline is the same

Native and non-native vowel discrimination in 6-month-old Norwegian infants

The current study will examine speech sound discrimination in Norwegian 6-month-old infants using a habituation-dishabituation paradigm. Two vowel contrasts will be tested: one native /y/-/i/, and one non-native, Southern British /ʌ/-/æ/. Infants will first hear one consonant-vowel syllable repeatedly (e.g., /by/), and after having habituated to it, they will hear four test trials. Two of these trials will contain the habituated syllable, and the other two will also introduce a novel syllable with the contrasting vowel (e.g., /bi/). If infants have longer looks to the test trials with the novel syllable compared to the habituated syllable, we suggest that they are able to detect the change in vowel identity (e.g., from /y/ to /i/), The same procedure will be adopted for the non-native vowel contrast. We expect discrimination of the native vowel contrast, and, given that perceptual attunement towards the speech sounds of the native language occurs between 8 to 10 months, we also expect discrimination of the non-native vowel contrasts

Voice onset time in Norwegian infant-directed speech over development

The current study will examine the voice onset time (VOT) of stop consonants in infant-directed speech (IDS) to 6, 9 and 12-month-old Norwegian infants, and will assess whether the articulatory properties of IDS related to VOT (difference in length, difference in contrast between voiced and voiceless etc.) are related to the infants' production of stop consonants. The data was collected at the BabyLing lab at the University of Oslo, Norway, from parents speaking Norwegian, and parental input was recorded in the lab. Both IDS and ADS were elicited via a storybook reading task from the child's main caregiver that was either the child's mother or father

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

Previous research on infant-directed speech (IDS) and its role in infants’ language development has largely focused on mothers, with fathers being investigated scarcely, if at all. Here we examine the acoustics of IDS as compared to adult-directed speech (ADS) in Norwegian mothers and fathers to 8–month-old infants, and whether these relate to direct (eye-tracking) and indirect (parental report) measures of infants’ word comprehension. Forty- five parent-infant dyads participated in the study. Parents (24 mothers, 21 fathers) were recorded reading a picture book to their infant (IDS), and to an experimenter (ADS), ensuring identical linguistic context across speakers and registers. Results showed that both mothers’ and fathers’ IDS had exaggerated prosody, expanded vowel spaces, and more variable and less distinct vowels. We found no evidence that acoustic features of parents’ speech were associated with infants’ word comprehension, suggesting that a facilitating role of IDS may appear later in development