Experience with research paradigms relates to infants' direction of preference

German infants' discrimination of the English /æ/-/ɛ/ contrast: Evidence from a cross-sectional and a longitudinal study

Young infants can discriminate many non-native sounds, but the discrimination ability is thought to decrease within the first year of life due to perceptual attunement. However, most studies tested infants' perception cross-sectionally, without examining within-group change. To this end, the current study tested German infants' discrimination of the English /æ/-/ɛ/ contrast both cross-sectionally and longitudinally using the visual habituation technique. In Experiment 1, 96 German-learning infants were tested cross-sectionally at 5-6, 8-9 and 12-13 months. Linear mixed-effects models revealed that while the 5-6-month-olds did not discriminate the contrast, the 8-9- and 12-13-month-olds showed signs of discrimination only when they were habituated with /ɛ/, in line with previous findings suggesting that changes from central to peripheral vowels in the F1/F2 vowel space are more noticeable than in the reverse direction. Moreover, the 8-9-month-olds showed a novelty preference, while the 12-13-month-olds showed a familiarity preference. In Experiment 2, the infants tested at 5-6 months in Experiment 1 were tested again at 8-9 and 12-13 months. Fifteen infants completed the three experiments. Here, only the 12-13-month-olds discriminated the contrast by showing a novelty preference but only when habituated with /æ/. Overall, both experiments showed gradual development of discrimination ability across the first year, which challenges the assumptions of perceptual attunement. We propose that the perceptual sensitivity for a non-native vocalic contrast can improve during development. The change in perceptual asymmetry tells us that the direction of asymmetry is not universal and can be altered by linguistic experience. The change from novelty to familiarity preference may be due to the emerging preference for the more native-like vowel as well as the effect of repeating experiments with the same infants. In sum, our cross-sectional and longitudinal results overlap broadly, but the potential effect of repeating experiments must be considered when interpreting longitudinal studies.

e-Babylab: An open-source browser-based tool for unmoderated online developmental studies

The COVID-19 pandemic massively changed the context and feasibility of developmental research. This new reality, as well as considerations about sample diversity and naturalistic settings for developmental research, highlights the need for solutions for online studies. In this article, we present e-Babylab, an open-source browser-based tool for unmoderated online studies targeted for young children and babies. e-Babylab offers an intuitive graphical user interface for study creation and management of studies, users, participant data, and stimulus material, with no programming skills required. Various kinds of audiovisual media can be presented as stimuli, and possible measures include webcam recordings, audio recordings, key presses, mouse-click/touch coordinates, and reaction times. An additional feature of e-Babylab is the possibility to administer short adaptive versions of MacArthur-Bates Communicative Development Inventories (Chai et al. Journal of Speech, Language, and Hearing Research, 63, 3488-3500, 2020). Information pages, consent forms, and participant forms are customizable. e-Babylab has been used with a variety of measures and paradigms in over 12 studies with children aged 12 months to 8 years (n = 1516). We briefly summarize some results of these studies to demonstrate that data quality, participant engagement, and overall results are comparable between laboratory and online settings. Finally, we discuss helpful tips for using e-Babylab and present plans for upgrades.

Limited evidence of test-retest reliability in infant-directed speech preference in a large preregistered infant experiment

Test-retest reliability-establishing that measurements remain consistent across multiple testing sessions-is critical to measuring, understanding, and predicting individual differences in infant language development. However, previous attempts to establish measurement reliability in infant speech perception tasks are limited, and reliability of frequently used infant measures is largely unknown. The current study investigated the test-retest reliability of infants' preference for infant-directed speech over adult-directed speech in a large sample (N = 158) in the context of the ManyBabies1 collaborative research project. Labs were asked to bring in participating infants for a second appointment retesting infants on their preference for infant-directed speech. This approach allowed us to estimate test-retest reliability across three different methods used to investigate preferential listening in infancy: the head-turn preference procedure, central fixation, and eye-tracking. Overall, we found no consistent evidence of test-retest reliability in measures of infants' speech preference (overall r = 0.09, 95% CI [-0.06,0.25]). While increasing the number of trials that infants needed to contribute for inclusion in the analysis revealed a numeric growth in test-retest reliability, it also considerably reduced the study's effective sample size. Therefore, future research on infant development should take into account that not all experimental measures may be appropriate for assessing individual differences between infants. RESEARCH HIGHLIGHTS: We assessed test-retest reliability of infants' preference for infant-directed over adult-directed speech in a large pre-registered sample (N = 158). There was no consistent evidence of test-retest reliability in measures of infants' speech preference. Applying stricter criteria for the inclusion of participants may lead to higher test-retest reliability, but at the cost of substantial decreases in sample size. Developmental research relying on stable individual differences should consider the underlying reliability of its measures.

First steps into the pupillometry multiverse of developmental science

Pupillometry has been widely implemented to investigate cognitive functioning since infancy. Like most psychophysiological and behavioral measures, it implies hierarchical levels of arbitrariness in preprocessing before statistical data analysis. By means of an illustrative example, we checked the robustness of the results of a familiarization procedure that compared the impact of audiovisual and visual stimuli in 12-month-olds. We adopted a multiverse approach to pupillometry data analysis to explore the role of (1) the preprocessing phase, that is, handling of extreme values, selection of the areas of interest, management of blinks, baseline correction, participant inclusion/exclusion and (2) the modeling structure, that is, the incorporation of smoothers, fixed and random effects structure, in guiding the parameter estimation. The multiverse of analyses shows how the preprocessing steps influenced the regression results, and when visual stimuli plausibly predicted an increase of resource allocation compared with audiovisual stimuli. Importantly, smoothing time in statistical models increased the plausibility of the results compared to those nested models that do not weigh the impact of time. Finally, we share theoretical and methodological tools to move the first steps into (rather than being afraid of) the inherent uncertainty of infant pupillometry.

Abstract processing of syllabic structures in early infancy

Syllables are one of the fundamental building blocks of early language acquisition. From birth onwards, infants preferentially segment, process and represent the speech into syllable-sized units, raising the question of what type of computations infants are able to perform on these perceptual units. Syllables are abstract units structured in a way that allows grouping phonemes into sequences. The goal of this research was to investigate 4-to-5-month-old infants' ability to encode the internal structure of syllables, at a target age when the language system is not yet specialized on the sounds and the phonotactics of native languages. We conducted two experiments in which infants were first familiarized to lists of syllables implementing either CVC (consonant-vowel-consonant) or CCV (consonant-consonant-vowel) structures, then presented with new syllables implementing both structures at test. Experiments differ in the degree of phonological similarity between the materials used at familiarization and test. Results show that infants were able to differentiate syllabic structures at test, even when test syllables were implemented by combinations of phonemes that infants did not hear before. Only infants familiarized with CVC syllables discriminated the structures at test, pointing to a processing advantage for CVC over CCV structures. This research shows that, in addition to preferentially processing the speech into syllable-sized units, during the first months of life, infants are also capable of performing fine-grained computations within such units.

Attention to novelty interferes with toddlers' emerging memory decision-making

Memory decision-making in 26- to 32-month-olds was investigated using visual-paired comparison paradigms, requiring toddlers to select familiar stimuli (Active condition) or view familiar and novel stimuli (Passive condition). In Experiment 1 (N = 108, 54.6% female, 62% White; replication N = 98), toddlers with higher accuracy in the Active condition showed reduced novelty preference in that condition, but not in the Passive condition (d = -.11). In Experiment 2 (N = 78; 52.6% female; 70.5% White), a brief 5% increase in target size boosted gaze transitions across conditions (d = .50) and accuracy in the Active condition (d = .53). Overall, evidence suggests that better attentional distribution can support decision-making. Research was conducted between 2014 and 2020 in Northern California.

Infant-directed song potentiates infants' selective attention to adults' mouths over the first year of life

The mechanisms by which infant-directed (ID) speech and song support language development in infancy are poorly understood, with most prior investigations focused on the auditory components of these signals. However, the visual components of ID communication are also of fundamental importance for language learning: over the first year of life, infants' visual attention to caregivers' faces during ID speech switches from a focus on the eyes to a focus on the mouth, which provides synchronous visual cues that support speech and language development. Caregivers' facial displays during ID song are highly effective for sustaining infants' attention. Here we investigate if ID song specifically enhances infants' attention to caregivers' mouths. 299 typically developing infants watched clips of female actors engaging them with ID song and speech longitudinally at six time points from 3 to 12 months of age while eye-tracking data was collected. Infants' mouth-looking significantly increased over the first year of life with a significantly greater increase during ID song versus speech. This difference was early-emerging (evident in the first 6 months of age) and sustained over the first year. Follow-up analyses indicated specific properties inherent to ID song (e.g., slower tempo, reduced rhythmic variability) in part contribute to infants' increased mouth-looking, with effects increasing with age. The exaggerated and expressive facial features that naturally accompany ID song may make it a particularly effective context for modulating infants' visual attention and supporting speech and language development in both typically developing infants and those with or at risk for communication challenges. A video abstract of this article can be viewed at https://youtu.be/SZ8xQW8h93A. RESEARCH HIGHLIGHTS: Infants' visual attention to adults' mouths during infant-directed speech has been found to support speech and language development. Infant-directed (ID) song promotes mouth-looking by infants to a greater extent than does ID speech across the first year of life. Features characteristic of ID song such as slower tempo, increased rhythmicity, increased audiovisual synchrony, and increased positive affect, all increase infants' attention to the mouth. The effects of song on infants' attention to the mouth are more prominent during the second half of the first year of life.

Towards a model of language neurobiology in early development

Understanding language neurobiology in early childhood is essential for characterizing the developmental structural and functional changes that lead to the mature adult language network. In the last two decades, the field of language neurodevelopment has received increasing attention, particularly given the rapid advances in the implementation of neuroimaging techniques and analytic approaches that allow detailed investigations into the developing brain across a variety of cognitive domains. These methodological and analytical advances hold the promise of developing early markers of language outcomes that allow diagnosis and clinical interventions at the earliest stages of development. Here, we argue that findings in language neurobiology need to be integrated within an approach that captures the dynamic nature and inherent variability that characterizes the developing brain and the interplay between behavior and (structural and functional) neural patterns. Accordingly, we describe a framework for understanding language neurobiology in early development, which minimally requires an explicit characterization of the following core domains: i) computations underlying language learning mechanisms, ii) developmental patterns of change across neural and behavioral measures, iii) environmental variables that reinforce language learning (e.g., the social context), and iv) brain maturational constraints for optimal neural plasticity, which determine the infant's sensitivity to learning from the environment. We discuss each of these domains in the context of recent behavioral and neuroimaging findings and consider the need for quantitatively modeling two main sources of variation: individual differences or trait-like patterns of variation and within-subject differences or state-like patterns of variation. The goal is to enable models that allow prediction of language outcomes from neural measures that take into account these two types of variation. Finally, we examine how future methodological approaches would benefit from the inclusion of more ecologically valid paradigms that complement and allow generalization of traditional controlled laboratory methods.

Fine-tuning language discrimination: Bilingual and monolingual infants' detection of language switching

The ability to differentiate between two languages sets the stage for bilingual learning. Infants can discriminate languages when hearing long passages, but language switches often occur on short time scales with few cues to language identity. As bilingual infants begin learning sequences of sounds and words, how do they detect the dynamics of two languages? In two studies using the head-turn preference procedure, we investigated whether infants (n = 44) can discriminate languages at the level of individual words. In Study 1, bilingual and monolingual 8- to 12-month-olds were tested on their detection of single-word language switching in lists of words (e.g., "dog… lait [fr. milk]"). In Study 2, they were tested on language switching within sentences (e.g., "Do you like the lait?"). We found that infants were unable to detect language switching in lists of words, but the results were inconclusive about infants' ability to detect language switching within sentences. No differences were observed between bilinguals and monolinguals. Given that bilingual proficiency eventually requires detection of sound sequences across two languages, more research will be needed to conclusively understand when and how this skill emerges. Materials, data, and analysis scripts are available at https://osf.io/9dtwn/.

Research at a Distance: Replicating Semantic Differentiation Effects Using Remote Data Collection With Children Participants

Remote data collection procedures can strengthen developmental science by addressing current limitations to in-person data collection and helping recruit more diverse and larger samples of participants. Thus, remote data collection opens an opportunity for more equitable and more replicable developmental science. However, it remains an open question whether remote data collection procedures with children participants produce results comparable to those obtained using in-person data collection. This knowledge is critical to integrate results across studies using different data collection procedures. We developed novel web-based versions of two tasks that have been used in prior work with 4-6-year-old children and recruited children who were participating in a virtual enrichment program. We report the first successful remote replication of two key experimental effects that speak to the emergence of structured semantic representations (N = 52) and their role in inferential reasoning (N = 40). We discuss the implications of these findings for using remote data collection with children participants, for maintaining research collaborations with community settings, and for strengthening methodological practices in developmental science.

Perceptual sensitivity to vowel quality and vowel length in the first year of life

The perceptual attunement to native vowel categories has been reported to occur at 6 months of age. However, some languages contrast vowels both in quality and in length, and whether and how the acquisition of spectral and duration-cued contrasts differs is uncertain. This study traced the development of infants' sensitivity to native (Czech) vowel-length and vowel-quality contrasts. The results suggest that in a vowel-length language, infants learn to categorize vowels in terms of length earlier and/or more robustly than in terms of quality, the representation of which may still be relatively underdeveloped at 10 months of age.