Greater attention to socioeconomic status in developmental research can improve the external validity, generalizability, and replicability of developmental science.

Psychological researchers have been criticized for making broad presumptions about human behavior based on limited sampling. In part, presumptive generalizability is reflected in the limited representation of sociodemographic variation in research reports. In this analysis, we examine time-trends in reporting of a key sociodemographic construct relevant to many aspects of child development-socioeconomic status (SES)-across six mainstream developmental journals (Infancy, Child Development, Developmental Science, Developmental Psychology, Infant and Child Development, and Infant Behavior & Development) between 2016 and 2022. Findings point to limited reporting of SES across developmental journals and across time. Reporting rates varied significantly by region and by topic of development. In terms of specific indicators of SES, there was consistent use of income and caregiver education as SES indicators. The epistemic costs of the lack of integration of socio-economic factors in developmental research are addressed. Pathways to greater integration of SES are proposed. RESEARCH HIGHLIGHTS: We analyzed reporting and representation of socioeconomic status in published studies on early child development. A large proportion of published studies did not report any socio-economic information. Suggestions for greater attention to socioeconomic status are proposed.

Effects of environmental diversity on exploration and learning: The case of bilingualism.

Bilingual environments provide a commonplace example of increased complexity and uncertainty. Learning multiple languages entails mastery of a larger and more variable range of sounds, words, syntactic structures, pragmatic conventions, and more complex mapping of linguistic information to objects in the world. Recent research suggests that bilingual learners demonstrate fundamental variation in how they explore and learn from their environment, which may derive from this increased complexity. In particular, the increased complexity and variability of bilingual environments may broaden the focus of learners' attention, laying a different attentional foundation for learning. In this review, we introduce a novel framework, with accompanying empirical evidence, for understanding how early learners may adapt to a more complex environment, drawing on bilingualism as an example. Three adaptations, each relevant to the demands of abstracting structure from a complex environment, are introduced. Each adaptation is discussed in the context of empirical evidence attesting to shifts in basic psychological processes in bilingual learners. This evidence converges on the notion that bilingual learners may explore their environment more broadly. Downstream consequences of broader sampling for perception and learning are discussed. Finally, recommendations for future research to expand the scientific narrative on the impact of diverse environments on learning are provided. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

A unified approach to demographic data collection for research with young children across diverse cultures.

Culture is a key determinant of children's development both in its own right and as a measure of generalizability of developmental phenomena. Studying the role of culture in development requires information about participants' demographic backgrounds. However, both reporting and treatment of demographic data are limited and inconsistent in child development research. A barrier to reporting demographic data in a consistent fashion is that no standardized tool currently exists to collect these data. Variation in cultural expectations, family structures, and life circumstances across communities make the creation of a unifying instrument challenging. Here, we present a framework to standardize demographic reporting for early child development (birth to 3 years of age), focusing on six core sociodemographic construct categories: biological information, gestational status, health status, community of descent, caregiving environment, and socioeconomic status. For each category, we discuss potential constructs and measurement items and provide guidance for their use and adaptation to diverse contexts. These items are stored in an open repository of context-adapted questionnaires that provide a consistent approach to obtaining and reporting demographic information so that these data can be archived and shared in a more standardized format. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The development of tone discrimination in infancy: Evidence from a cross-linguistic, multi-lab report.

We report the findings of a multi-language and multi-lab investigation of young infants' ability to discriminate lexical tones as a function of their native language, age and language experience, as well as of tone properties. Given the high prevalence of lexical tones across human languages, understanding lexical tone acquisition is fundamental for comprehensive theories of language learning. While there are some similarities between the developmental course of lexical tone perception and that of vowels and consonants, findings for lexical tones tend to vary greatly across different laboratories. To reconcile these differences and to assess the developmental trajectory of native and non-native perception of tone contrasts, this study employed a single experimental paradigm with the same two pairs of Cantonese tone contrasts (perceptually similar vs. distinct) across 13 laboratories in Asia-Pacific, Europe and North-America testing 5-, 10- and 17-month-old monolingual (tone, pitch-accent, non-tone) and bilingual (tone/non-tone, non-tone/non-tone) infants. Across the age range and language backgrounds, infants who were not exposed to Cantonese showed robust discrimination of the two non-native lexical tone contrasts. Contrary to this overall finding, the statistical model assessing native discrimination by Cantonese-learning infants failed to yield significant effects. These findings indicate that lexical tone sensitivity is maintained from 5 to 17 months in infants acquiring tone and non-tone languages, challenging the generalisability of the existing theoretical accounts of perceptual narrowing in the first months of life. RESEARCH HIGHLIGHTS: This is a multi-language and multi-lab investigation of young infants' ability to discriminate lexical tones. This study included data from 13 laboratories testing 5-, 10-, and 17-month-old monolingual (tone, pitch-accent, non-tone) and bilingual (tone/non-tone, non-tone/non-tone) infants. Overall, infants discriminated a perceptually similar and a distinct non-native tone contrast, although there was no evidence of a native tone-language advantage in discrimination. These results demonstrate maintenance of tone discrimination throughout development.

Bilingual infants readily orient to novel visual stimuli.

Bilingualism has been shown to modify infants' responses in a range of domains. In particular, early bilingual experience is associated with greater flexibility and openness in infant perception and learning. In this study, we investigated whether bilingual infants demonstrate more fundamental differences in how they explore their environment in ways that could contribute to greater openness. Specifically, we investigated whether bilingual infants orient more rapidly to new information. Capitalizing on a classic paradigm by Fantz (1964), monolingual and bilingual infants (5-6 months and 8-9 months) were simultaneously presented with familiar and novel stimuli. As they received increased exposure to the familiar and novel stimuli, monolingual infants demonstrated a null preference, followed by a novelty preference, as previously evidenced in Fantz's study. In contrast, an orientation toward novelty emerged more readily in bilingual infants. Characteristics of a bilingual environment that may modulate the allocation of attention toward novelty are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Diversity and representation in infant research: Barriers and bridges toward a globalized science of infant development.

Psychological researchers have become increasingly concerned with generalized accounts of human behavior based on narrow participant representation. This concern is particularly germane to infant research as findings from infant studies are often invoked to theorize broadly about the origins of human behavior. In this article, we examined participant diversity and representation in research published on infant development in four journals over the past decade. Sociodemographic data were coded for all articles reporting infant data published in Child Development, Developmental Science, Developmental Psychology, and Infancy between 2011 and 2022. Analyses of 1682 empirical articles, sampling approximately 1 million participants, revealed consistent under-reporting of sociodemographic information. For studies that reported sociodemographic characteristics, there was an unwavering skew toward White infants from North America/Western Europe. To address a lack of diversity in infant studies and its scientific impact, a set of principles and practices are proposed to advance toward a more globally representative science.

Effects of face masks on language comprehension in bilingual children.

Due to the COVID-19 pandemic, many children receive language input through face coverings. The impact of face coverings for children's abilities to understand language remains unclear. Past research with monolingual children suggests that hearing words through surgical masks does not disrupt word recognition, but hearing words through transparent face shields proves more challenging. In this study, we investigated effects of different face coverings (surgical masks and transparent face shields) on language comprehension in bilingual children. Three-year-old English-Mandarin bilingual children (N = 28) heard familiar words in both English and Mandarin spoken through transparent face shields, surgical masks, and without masks. When tested in English, children recognized words presented without a mask and through a surgical mask, but did not recognize words presented with transparent face shields, replicating past findings with monolingual children. In contrast, when tested in Mandarin, children recognized words presented without a mask, through a surgical mask, and through a transparent face shield. Results are discussed in terms of specific properties of English and Mandarin that may elicit different effects for transparent face shields. Overall, the present findings suggest that face coverings, and in particular, surgical masks do not disrupt spoken word recognition in young bilingual children.

Effects of socio-economic status on infant native and non-native phoneme discrimination.

Infants undergo fundamental shifts in perception that are reported to be critical for language acquisition. In particular, infants' perception of native and non-native sounds begins to align with the properties of their native sound system. Thus far, empirical evidence for this transition - perceptual narrowing - has drawn from socio-economically and linguistically narrow populations from limited world regions. In this study, infants were sampled across diverse socio-economic strata and linguistic development in Singapore. One hundred and 16 infants were tested on their ability to discriminate both a native phonetic contrast (/ba/ versus /da/) and a non-native Hindi contrast (/ta/ versus /ʈa). Infants ranged in age from 6 to 12 months. Associations between age and discrimination varied by contrast type. Results demonstrated that infants' native sensitivities were positively predicted by family SES, whereas non-native sensitivities were not. Maternal socio-economic factors uniquely predicted native language sensitivity. Findings suggest that infants' sensitivity to native sound contrasts is influenced by their family socio-economic status. RESEARCH HIGHLIGHTS: We investigated effects of socio-economic status on infant speech perception. Infants were tested on native and non-native speech discrimination. Socio-economic status predicted native speech discrimination. Maternal occupation was a key predictor of native speech discrimination.

The home literacy environment mediates effects of socio-economic status on infant vocabulary development.

It is well attested that high socio-economic status (SES) is associated with larger vocabulary size estimates in young children. This has led to growing interest in identifying associations and mechanisms that may contribute to this relationship. In this study, parent-child reading behaviors were investigated in relation to vocabulary size in a large-scale study of linguistically and socio-economically diverse families. This study sampled 902 infants in Singapore, a multilingual society. Both single-language (dominant and non-dominant) and dual-language vocabulary size estimates were obtained and related to family SES, demographic details, and home literacy activities. Results demonstrated that both single-language (dominant and non-dominant) and dual-language infant vocabulary size estimates were predicted by parental education levels. Further analyses revealed that parent-child book reading activities mediated the relationship between parental education and infant vocabulary size. Findings suggest that shared book reading may narrow effects of socio-economic disparities on early language development. RESEARCH HIGHLIGHTS: Socio-economic status (SES) was examined in relation to infant vocabulary size in a linguistically and socio-economically diverse setting. Mediating effects of the home literacy environment on infant vocabulary size were measured. Socio-economic factors, notably parental education, had both direct and indirect effects on vocabulary size. The home literacy environment mediated effects of SES on infant vocabulary size.

Sensitivity to visual cues within motion events in monolingual and bilingual infants.

It is well known that infants undergo developmental change in how they respond to language-relevant visual contrasts. For example, when viewing motion events, infants' sensitivities to background information ("ground-path cues," e.g., whether a background is flat and continuous or bounded) change with age. Prior studies with English and Japanese monolingual infants have demonstrated that 14-month-old infants discriminate between motion events that take place against different ground-paths (e.g., an unbounded field vs a bounded street). By 19 months of age, this sensitivity becomes more selective in monolingual infants; only learners of languages that lexically contrast these categories, such as Japanese, discriminate between such events. In this study, we investigated this progression in bilingual infants. We first replicated past reports of an age-related decline in ground-path sensitivity from 14 to 19 months in English monolingual infants living in a multilingual society. English-Mandarin bilingual infants living in that same society were then tested on discrimination of ground-path cues at 14, 19, and 24 months. Although neither the English nor Mandarin language differentiates motion events based on ground-path cues, bilingual infants demonstrated protracted sensitivity to these cues. Infants exhibited a lack of discrimination at 14 months, followed by discrimination at 19 months and a subsequent decline in discrimination at 24 months. In addition, bilingual infants demonstrated more fine-grained sensitivities to subtle ground cues not observed in monolingual infants.

The tone atlas of perceptual discriminability and perceptual distance: Four tone languages and five language groups.

Some prior investigations suggest that tone perception is flexible, reasonably independent of native phonology, whereas others suggest it is constrained by native phonology. We address this issue in a systematic and comprehensive investigation of adult tone perception. Sampling from diverse tone and non-tone speaking communities, we tested discrimination of the three major tone systems (Cantonese, Thai, Mandarin) that dominate the tone perception literature, in relation to native language and language experience as well as stimulus variation (tone properties, presentation order, pitch cues) using linear mixed effect modelling and multidimensional scaling. There was an overall discrimination advantage for tone language speakers and for native tones. However, language- and tone-specific effects, and presentation order effects also emerged. Thus, over and above native phonology, stimulus variation exerts a powerful influence on tone discrimination. This study provides a tone atlas, a reference guide to inform empirical studies of tone sensitivity, both retrospectively and prospectively.

Improving the generalizability of infant psychological research: The ManyBabies model.

Yarkoni's analysis clearly articulates a number of concerns limiting the generalizability and explanatory power of psychological findings, many of which are compounded in infancy research. ManyBabies addresses these concerns via a radically collaborative, large-scale and open approach to research that is grounded in theory-building, committed to diversification, and focused on understanding sources of variation.

Effects of interracial experience on the race preferences of infants.

Over their first year of life, infants express visual preferences for own- versus other-race faces. This developmental transition has primarily been investigated in monoracial societies where infants have limited personal or societal contact with other races. We investigated whether previously reported visual preferences for race generalize to a multiracial society (i.e., Singapore). In addition, we investigated effects of caregiver race on visual preferences for race. In Experiment 1, race preferences were measured at 3, 6, and 9 months of age for own-race (Chinese) versus other-race (Indian) faces in infants with no regular interaction with Indian-race individuals. Singaporean infants displayed a significant visual preference for Indian-race faces at each age group. Furthermore, infants raised with other-race caregivers demonstrated an age-related increase in other-race visual preferences. The visual preferences of infants for other-race faces were predicted by the extent of other-race contact. In Experiment 2, we confirmed that an other-race visual preference was not exclusive to Indian faces in a sample of 6-month-old Singaporean Chinese infants who demonstrated a similar other-race visual preference for Caucasian faces over Chinese faces. Findings are discussed in terms of the influence of other-race contact on visual preferences for race in infants.

Language acquisition in a multilingual society: English vocabulary norms and predictors in Singaporean children.

In this study, infant vocabulary development was tracked in a multilingual society (Singapore) within a socioeconomically diverse sample. The sample comprised 1316 infants from 17.4 to 27.7 months (669 females, 647 males; 88% Chinese race, 4% Malay, 4% Indian, and 0.004% mixed-race [4% declined to provide race information]). Children varied in English language exposure and socioeconomic status. Analyses focused on identifying demographic predictors of English vocabulary size in multilingually exposed infants. Adaptations of the Macarthur-Bates Communicative Development Inventory for English, Mandarin, and Malay are provided as well as English vocabulary norms that account for variation in English exposure. This manuscript reports the first set of English language norms-calibrated to English exposure-for multilingual infants in a non-Western setting.

Infants recognize words spoken through opaque masks but not through clear masks.

COVID-19 has modified numerous aspects of children's social environments. Many children are now spoken to through a mask. There is little empirical evidence attesting to the effects of masked language input on language processing. In addition, not much is known about the effects of clear masks (i.e., transparent face shields) versus opaque masks on language comprehension in children. In the current study, 2-year-old infants were tested on their ability to recognize familiar spoken words in three conditions: words presented with no mask, words presented through a clear mask, and words presented through an opaque mask. Infants were able to recognize familiar words presented without a mask and when hearing words through opaque masks, but not when hearing words through clear masks. Findings suggest that the ability of infants to recover spoken language input through masks varies depending on the surface properties of the mask.

Cognitive flexibility and parental education differentially predict implicit and explicit racial biases in bilingual children.

Prior research has suggested that bilingual children demonstrate reduced social bias relative to their monolingual peers. In particular, they exhibit less implicit bias against racial outgroups. However, the cognitive determinants of racial bias in bilingual children remain unclear. In the current study, relationships between racial bias and three cognitive factors (inhibitory control, cognitive flexibility, and perspective-taking ability), along with language proficiency and parental education, were investigated in a sample of bilingual preschoolers (N = 55). Children were bilingual learners of English and Mandarin. Results demonstrated that implicit bias was predicted by cognitive flexibility, independent of variation in inhibitory control, second language vocabulary, perspective taking, and parental education. In contrast, explicit bias was predicted by parental education alone and not by cognitive or linguistic factors. Findings suggest that increased cognitive flexibility, often thought to be an outgrowth of bilingual experience, may also be associated with a reduction in implicit bias. Findings are discussed in terms of specific mechanisms that may link cognitive factors, bilingualism, and racial bias.

A multi-lab study of bilingual infants: Exploring the preference for infant-directed speech.

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) than adult-directed speech (ADS). Yet, IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multi-site study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants' IDS preference. As part of the multi-lab ManyBabies 1 project, we compared lab-matched samples of 333 bilingual and 385 monolingual infants' preference for North-American English IDS (cf. ManyBabies Consortium, 2020: ManyBabies 1), tested in 17 labs in 7 countries. Those infants were tested in two age groups: 6-9 months (the younger sample) and 12-15 months (the older sample). We found that bilingual and monolingual infants both preferred IDS to ADS, and did not differ in terms of the overall magnitude of this preference. However, amongst bilingual infants who were acquiring North-American English (NAE) as a native language, greater exposure to NAE was associated with a stronger IDS preference, extending the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes a similar contribution to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments.

Beyond perceptual narrowing: Monolingual and bilingual infants discriminate Hindi contrasts when learning words in the second year of life.

A significant body of literature has demonstrated that infants demonstrate a decline in sensitivity to nonnative sound contrasts by their first birthday, a transition often thought to be adaptive for later word learning. The present study investigated infants' sensitivity to these contrasts in a habituation-based discrimination and word learning task (total N = 168, 78 males and 90 females). All infants were native to Singapore and were of Chinese origin. Family socioeconomic status (SES) was measured by parental education. The mean number of years of parental education was 4.02 years after high school. Using a habituation-based discrimination paradigm, monolingual, and bilingual infants' sensitivity to the Hindi dental/retroflex voiceless stop was investigated at 14 months (Experiment 1). Neither group discriminated the contrast. Using the Switch paradigm, we assessed sensitivity to the same contrast in a word learning task. Monolingual and bilingual infants were tested at 14- and 19 months (Experiment 2a) and subsequently, an older group of bilingual infants was tested at 24 months (Experiment 2b). Results demonstrated an overall sensitivity to the Hindi contrast in Experiment 2a. Bilingual infants tested in Experiment 2b were not sensitive to the Hindi contrast. Findings are discussed with reference to discontinuities in the growth of a phonological lexicon as well as possible mechanisms elicit nonnative sensitivity in word learning. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The development of gaze following in monolingual and bilingual infants: A multi-laboratory study.

Determining the meanings of words requires language learners to attend to what other people say. However, it behooves a young language learner to simultaneously encode relevant non-verbal cues, for example, by following the direction of their eye gaze. Sensitivity to cues such as eye gaze might be particularly important for bilingual infants, as they encounter less consistency between words and objects than monolingual infants, and do not always have access to the same word-learning heuristics (e.g., mutual exclusivity). In a preregistered study, we tested the hypothesis that bilingual experience would lead to a more pronounced ability to follow another's gaze. We used a gaze-following paradigm developed by Senju and Csibra (Current Biology, 18, 2008, 668) to test a total of 93 6- to 9-month-old and 229 12- to 15-month-old monolingual and bilingual infants, in 11 laboratories located in 8 countries. Monolingual and bilingual infants showed similar gaze-following abilities, and both groups showed age-related improvements in speed, accuracy, frequency, and duration of fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations to on-screen objects, whether or not they were cued by the actor. These results suggest that gaze sensitivity is a fundamental aspect of development that is robust to variation in language exposure.

Sensitivity to race in language comprehension in monolingual and bilingual infants.

Past studies suggest that monolingual and bilingual infants respond differently to race information in face discrimination and social learning tasks. In particular, bilingual infants have been shown to respond more similarly to own- and other-race individuals, in contrast to monolingual infants, who respond preferentially to own-race individuals. In the current study, we investigated monolingual and bilingual sensitivity to speaker race in spoken word recognition. Two-year-old infants were presented with spoken words in association with visual targets. Words were presented in association with own- or other-race actors and were either correctly pronounced or mispronounced. Measuring speech-responsive eye movements to visual targets, we analyzed fixation to visual targets for correct and mispronounced words in relation to speaker race for each group. When presented with own-race speakers, both monolingual and bilingual infants associated correctly pronounced labels, but not mispronounced labels, with visual targets. When presented with other-race speakers, bilingual infants responded similarly. In contrast, monolingual infants did not fixate visual targets regardless of whether words were correctly pronounced or mispronounced by an other-race speaker. Results are discussed in terms of the sensitivities of bilingual and monolingual infants to novelty, learned associations between race and language, and prior social experiences.