Self-recognition: From touching the body to knowing the self.

Recognizing oneself in a mirror is a classic test of self-concept. A new study has revealed the perceptual-motor foundations of conceptual self-knowledge: infants' success in the mirror test was accelerated after touching a tactile stimulus while viewing themselves in a mirror.

Comparing apples to manzanas and oranges to naranjas: A new measure of English-Spanish vocabulary for dual language learners.

The valid assessment of vocabulary development in dual-language-learning infants is critical to developmental science. We developed the Dual Language Learners English-Spanish (DLL-ES) Inventories to measure vocabularies of U.S. English-Spanish DLLs. The inventories provide translation equivalents for all Spanish and English items on Communicative Development Inventory (CDI) short forms; extended inventories based on CDI long forms; and Spanish language-variety options. Item-Response Theory analyses applied to Wordbank and Web-CDI data (n = 2603, 12-18 months; n = 6722, 16-36 months; half female; 1% Asian, 3% Black, 2% Hispanic, 30% White, 64% unknown) showed near-perfect associations between DLL-ES and CDI long-form scores. Interviews with 10 Hispanic mothers of 18- to 24-month-olds (2 White, 1 Black, 7 multi-racial; 6 female) provide a proof of concept for the value of the DLL-ES for assessing the vocabularies of DLLs.

How mothers help children learn to use everyday objects.

Children must learn specific motor actions to use everyday objects as their designers intended. However, designed actions are not obvious to children and often are difficult to implement. Children must know what actions to do and how to execute them. Previous work identified a protracted developmental progression in learning designed actions-from nondesigned exploratory actions, to display of the designed action, to successful implementation. Presumably, caregivers can help children to overcome the challenges in discovering and implementing designed actions. Mothers of 12-, 18- to 24-, and 30- to 36-month-olds (N = 74) were asked to teach their children to open containers with twist-off or pull-off lids. Mothers' manual and verbal input aligned with the developmental progression and with children's actions in the moment, pointing to the role of attuned social information in helping children learn to use objects for activities of daily living. However, mothers sometimes "overhelped" by implementing designed actions for children instead of getting children to do it themselves, highlighting the challenges of teaching novices difficult motor actions.

Within arms reach: Physical proximity shapes mother-infant language exchanges in real-time.

During everyday interactions, mothers and infants achieve behavioral synchrony at multiple levels. The ebb-and-flow of mother-infant physical proximity may be a central type of synchrony that establishes a common ground for infant-mother interaction. However, the role of proximity in language exchanges is relatively unstudied, perhaps because structured tasks-the common setup for observing infant-caregiver interactions-establish proximity by design. We videorecorded 100 mothers (U.S. Hispanic N = 50, U.S. Non-Hispanic N = 50) and their 13- to 23-month-old infants during natural activity at home (1-to-2 h per dyad), transcribed mother and infant speech, and coded proximity continuously (i.e., infants and mother within arms reach). In both samples, dyads entered proximity in a bursty temporal pattern, with bouts of proximity interspersed with bouts of physical distance. As hypothesized, Non-Hispanic and Hispanic mothers produced more words and a greater variety of words when within arms reach than out of arms reach. Similarly, infants produced more utterances that contained words when close to mother than when not. However, infants babbled equally often regardless of proximity, generating abundant opportunities to play with sounds. Physical proximity expands opportunities for language exchanges and infants' communicative word use, although babies accumulate massive practice babbling even when caregivers are not proximal.

Investigating associations between parent engagement and toddlers' mathematics performance.

Early mathematics skills relate to later mathematics achievement and educational attainment, which in turn predict career choice, income, health and financial decision-making. Critically, large differences exist among children in early mathematics performance, with parental mathematics engagement being a key predictor. However, most prior work has examined mothers' mathematics engagement with their preschool- and school-aged children. In this Registered Report, we tested concurrent associations between mothers' and fathers' engagement in mathematics activities with their 2- to 3-year-old toddlers and children's mathematics performance. Mothers and fathers did not differ in their engagement in mathematics activities, and both parents' mathematics engagement related to toddlers' mathematics skills. Fathers' mathematics engagement was associated with toddlers' number and mathematics language skills, but not their spatial skills. Mothers' mathematics engagement was only associated with toddlers' mathematics language skills. Critically, associations may be domain-specific, as parents' literacy engagement did not relate to measures of mathematics performance above their mathematics engagement. Mothers' and fathers' mathematics activities uniquely relate to toddlers' developing mathematics skills, and future work on the nuances of these associations is needed.

Gahvora cradling in Tajikistan: Cultural practices and associations with motor development.

In Tajikistan, infants are bound supine in a "gahvora" cradle that severely restricts movement. Does cradling affect motor development and body growth? In three studies (2013-2018), we investigated associations between time in the gahvora (within days and across age) and motor skills and flattened head dimensions in 8-24-month-old Tajik infants (N = 269, 133 girls, 136 boys)) and 4.3-5.1-year-old children (N = 91, 53 girls, 38 boys). Infants had later motor onset ages relative to World Health Organization standards and pronounced brachycephaly; cradling predicted walk onset age and the proficiency of sitting, crawling, and walking. By 4-5 years, children's motor skills were comparable with US norms. Cultural differences in early experiences offer a unique lens onto developmental processes and equifinality in development.

"Go, go, go!" Mothers' verbs align with infants' locomotion.

Caregivers often tailor their language to infants' ongoing actions (e.g., "are you stacking the blocks?"). When infants develop new motor skills, do caregivers show concomitant changes in their language input? We tested whether the use of verbs that refer to locomotor actions (e.g., "come," "bring," "walk") differed for mothers of 13-month-old crawling (N = 16) and walking infants (N = 16), and mothers of 18-month-old experienced walkers (N = 16). Mothers directed twice as many locomotor verbs to walkers compared to same-age crawlers, but mothers' locomotor verbs were similar for younger and older walkers. In real-time, mothers' use of locomotor verbs was dense when infants were locomoting, and sparse when infants were stationary, regardless of infants' crawler/walker status. Consequently, infants who spent more time in motion received more locomotor verbs compared to infants who moved less frequently. Findings indicate that infants' motor skills guide their in-the-moment behaviors, which in turn shape the language they receive from caregivers. RESEARCH HIGHLIGHTS: Infants' motor skills guide their in-the-moment behaviors, which in turn shape the language they receive from caregivers. Mothers directed more frequent and diverse verbs that referenced locomotion (e.g., "come," "go," "bring") to walking infants compared to same-aged crawling infants. Mothers' locomotor verbs were temporally dense when infants locomoted and sparse when infants were stationary, regardless of whether infants could walk or only crawl.

Mothers' and fathers' engagement in math activities with their toddler sons and daughters: The moderating role of parental math beliefs.

Parents' beliefs about the importance of math predicts their math engagement with their children. However, most work focuses on mothers' math engagement with preschool- and school-aged children, leaving gaps in knowledge about fathers and the experiences of toddlers. We examined differences in mothers' and fathers' (N = 94) engagement in math- and non-math activities with their two-year-old girls and boys. Parents reported their beliefs about the importance of math and literacy for young children and their frequency of home learning activities. Parents of sons did not differ in their engagement in math activities from parents of daughters. Mothers reported engaging more frequently in math activities with their toddlers than fathers did, but the difference reduced when parents endorsed stronger beliefs about the importance of math for children. Even at very early ages, children experience vastly different opportunities to learn math in the home, with math-related experiences being shaped by both parent gender and parents' beliefs.

The mountain stream of infant development.

Development is complex. It encompasses interacting domains, at multiple levels, across nested time scales. Embracing the complexity of development-while addressing the challenges inherent to studying infants-requires researchers to make tough decisions about what to study, why, how, where, and when. My own view is inspired by a developmental systems approach, and echoed in Esther Thelen's (2005) mountain stream metaphor. Like a river that carves its course, the active infant navigates the social and physical environment and generates rich inputs that propel learning and development. Drawing from my experiences, I offer some recommendations to guide research on infants. I encourage researchers to embrace discovery science; to observe infants in ecologically valid settings; to recognize the active and adaptive nature of infant behavior; to break down silos and consider the nonobvious; and to adopt full transparency in all aspects of research. I draw on cascading influences in infant play, language, and motor domains to illustrate the value of a bottom-up, cross-domain, collaborative approach.

The process of learning the designed actions of toys.

Many everyday objects require "hidden" affordances to use as designed (e.g., twist open a water bottle). Previous work found a reliable developmental progression in children's learning of designed actions with adult objects such as containers and zippers-from non-designed exploratory actions, to the basics of the designed action, to successful implementation. Many objects designed for children (e.g., toys) also entail designed actions (e.g., interlocking bricks) but might not require a protracted period of discovery and implementation. We encouraged 12- to 60-month-old children (n = 91) and a comparative sample of 20 adults to play with six Duplo bricks to test whether the developmental progression identified for children's learning of adult objects with hidden affordances holds for a popular toy expressly designed for children. We also examined whether children's moment-to-moment behaviors with Duplo bricks inform on general processes involved in discovery and implementation of hidden affordances. With age, children progressed from non-designed exploratory actions, to attempts to interlock, to success, suggesting that the three-step developmental progression revealed with everyday adult objects broadly applies to learning hidden affordances regardless of object type. Detailing the process of learning (the type and timing of children's non-designed actions and attempts to interlock) revealed that the degree of lag between steps of the progression depends on the transparency of the required actions, the availability of perceptual feedback, and the difficulty of the perceptual-motor requirements. Findings provide insights into factors that help or hinder learning of hidden affordances.

Object play in the everyday home environment generates rich opportunities for infant learning.

Infants everywhere engage with objects throughout the day, even if the objects of play differ across cultures. Indeed, object play is a universal context for learning. Yet, the characteristics of object play at home remain largely unexamined, especially in infants from non-English-speaking backgrounds. Through frame-by-frame video coding, we documented Hispanic infants' object interactions based on 1-2 h of naturalistic home observations. Infants interacted with a wide variety of toys and household objects in brief bouts that summed to ~60% of their time. As infants transition among objects, they serendipitously generate opportunities for learning that support development across domains.

Mothers talk about infants' actions: How verbs correspond to infants' real-time behavior.

Infants learn nouns during object-naming events-moments when caregivers name the object of infants' play (e.g., ball as infant holds a ball). Do caregivers also label the actions of infants' play (e.g., roll as infant rolls a ball)? We investigated connections between mothers' verb inputs and infants' actions. We video-recorded 32 infant-mother dyads for 2 hr at home (13 month olds, n = 16; 18 month olds, n = 16; girls, n = 16; White, n = 23; Asian, n = 2; Black, n = 1; other, n = 1; multiple races, n = 5; Hispanic/Latinx, n = 2). Dyads were predominantly from middle-class to upper middle-class households. We identified each manual verb (e.g., press, shake) and whole-body verb (e.g., kick, go) that mothers directed to infants. We coded whether infants displayed manual and/or whole-body actions during a 6-s window surrounding the verb (i.e., 3 s prior and 3 s after the named verb). Mothers' verbs and infant actions were largely congruent: Whole-body verbs co-occurred with whole-body actions, and manual verbs co-occurred with manual actions. Moreover, half of mothers' verbs corresponded precisely to infants' concurrent action (e.g., infant pressed button as mother said, "Press the button"). In most instances, mothers commented on rather than instigated infants' actions. Findings suggest that verb learning is embodied, such that infants' motor actions offer powerful cues to verb meanings. Furthermore, our approach highlights the value of cross-domain research integrating infants' developing motor and language skills to understand word learning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Infants' object interactions are long and complex during everyday joint engagement.

As infants interact with the object world, they generate rich information about object properties and functions. Much of infant learning unfolds in the presence of caregivers, who talk about and act on the objects of infant play. Does mother joint engagement correspond to real-time changes in the complexity and duration of infant object interactions? We observed 38 mothers and their first-born infants (cross-sectional, 13, 18, and 23 months) during 2 h of everyday activity as infants freely navigated their home environments. Behavioral coding explored thousands of infant object interactions within and outside mother joint engagement. Object interactions involving exclusively simple play were shorter than complex play bouts. Critically, mothers' multimodal input (i.e., touching/gesturing toward and talking about the focal object) corresponded with more complex and longer play bouts than when mothers provided no input. Bouts involving complex play and multimodal input lasted 7.5 times longer than simple play bouts absent mother input. Moreover, "action-orienting talk" (e.g., "Twist it", "Feed dolly"), rather than talk per se, corresponded with longer bout duration and complexity. Notably, the association between joint engagement and play duration was not a function of mothers having more time to join. Analyses that eliminated short infant bouts and considered the timing of mothers' behaviors confirmed that mother input "extended" the duration of play bouts. As infants actively explore their environments, their object interactions change moment to moment in the presence of mothers' multimodal engagement.

Joint engagement in the home environment is frequent, multimodal, timely, and structured.

Infants develop in a social context, surrounded by knowledgeable caregivers who scaffold learning through shared engagement with objects. However, researchers have typically examined joint engagement in structured tasks, where caregivers sit near infants and display frequent, prompt, and multimodal behaviors around the objects of infant action. Which features of joint engagement generalize to the real-world? Despite the importance of joint engagement for infant learning, critical assumptions around joint engagement in everyday interaction remain unexamined. We investigated behavioral and temporal features of joint engagement in the home environment, where objects for play abound and dyad proximity fluctuates. Infant manual actions, mother manual and verbal behaviors, and dyad proximity were coded frame-by-frame from 2-h naturalistic recordings of 13- to 23-month-old infants and their mothers (N = 38). Infants experienced rich, highly structured, multimodal mother input around the objects of their actions. Specifically, joint engagement occurred within seconds of infant action and was amplified in the context of interpersonal proximity. Findings validate laboratory-based research on characteristics of joint engagement while highlighting unique properties around the role of mother-infant proximity and temporal structuring of caregiver input over extended time frames. Implications for the social contexts that support infant learning and development are discussed.

Infant exuberant object play at home: Immense amounts of time-distributed, variable practice.

Object play yields enormous benefits for infant development. However, little is known about natural play at home where most object interactions occur. We conducted frame-by-frame video analyses of spontaneous activity in two 2-h home visits with 13-month-old crawling infants and 13-, 18-, and 23-month-old walking infants (N = 40; 21 boys; 75% White). Regardless of age, for every infant and time scale, across 10,015 object bouts, object interactions were short (median = 9.8 s) and varied (transitions among dozens of toys and non-toys) but consumed most of infants' time. We suggest that infant exuberant object play-immense amounts of brief, time-distributed, variable interactions with objects-may be conducive to learning object properties and functions, motor skill acquisition, and growth in cognitive, social, and language domains.

A Longitudinal Study of Language Use During Early Mother-Child Interactions in Spanish-Speaking Families Experiencing Low Income.

PURPOSE: This longitudinal study assessed continuity and stability of productive language (vocabulary and grammar) and discourse features (turn-taking; asking and responding to questions) during mother-child play. METHOD: Parent-child language use in 119 Spanish-speaking, Mexican immigrant mothers and their children at two ages (M = 2.5 and 3.6 years) was evaluated from transcriptions of interactions. RESULTS: Child productive language significantly increased over the year, whereas mothers showed commensurate increases in vocabulary diversity but very little change in grammatical complexity. Mother-child discourse was characterized by discontinuity: Mothers decreased their turn length and asked fewer questions while children increased on both measures. Rates of responding to questions remained high for both mothers and children even as children increased and mothers decreased over time. Mothers and children showed significant rank-order stability in productive language and measures of discourse. Mothers' rate of asking questions and children's responses to questions during the first interaction predicted children's receptive vocabulary a year later. CONCLUSIONS: As children become more sophisticated communicators, language input remains important, with discourse features growing in relevance. Children's early opportunities to respond to parents' questions in the context of play benefit their language skills. This work extends the evidence base from monolingual English-speaking families and is interpreted in the context of prior research on parenting practices in U.S. families of Mexican origin.

(Hyper)active Data Curation: A Video Case Study from Behavioral Science.

Video data are uniquely suited for research reuse and for documenting research methods and findings. However, curation of video data is a serious hurdle for researchers in the social and behavioral sciences, where behavioral video data are obtained session by session and data sharing is not the norm. To eliminate the onerous burden of post hoc curation at the time of publication (or later), we describe best practices in active data curation-where data are curated and uploaded immediately after each data collection to allow instantaneous sharing with one button press at any time. Indeed, we recommend that researchers adopt "hyperactive" data curation where they openly share every step of their research process. The necessary infrastructure and tools are provided by Databrary-a secure, web-based data library designed for active curation and sharing of personally identifiable video data and associated metadata. We provide a case study of hyperactive curation of video data from the Play and Learning Across a Year (PLAY) project, where dozens of researchers developed a common protocol to collect, annotate, and actively curate video data of infants and mothers during natural activity in their homes at research sites across North America. PLAY relies on scalable standardized workflows to facilitate collaborative research, assure data quality, and prepare the corpus for sharing and reuse throughout the entire research process.

Measuring Emerging Number Knowledge in Toddlers.

Recent evidence suggests that infants and toddlers may recognize counting as numerically relevant long before they are able to count or understand the cardinal meaning of number words. The Give-N task, which asks children to produce sets of objects in different quantities, is commonly used to test children's cardinal number knowledge and understanding of exact number words but does not capture children's preliminary understanding of number words and is difficult to administer remotely. Here, we asked whether toddlers correctly map number words to the referred quantities in a two-alternative forced choice Point-to-X task (e.g., "Which has three?"). Two- to three-year-old toddlers (N = 100) completed a Give-N task and a Point-to-X task through in-person testing or online via videoconferencing software. Across number-word trials in Point-to-X, toddlers pointed to the correct image more often than predicted by chance, indicating that they had some understanding of the prompted number word that allowed them to rule out incorrect responses, despite limited understanding of exact cardinal values. No differences in Point-to-X performance were seen for children tested in-person versus remotely. Children with better understanding of exact number words as indicated on the Give-N task also answered more trials correctly in Point-to-X. Critically, in-depth analyses of Point-to-X performance for children who were identified as 1- or 2-knowers on Give-N showed that 1-knowers do not show a preliminary understanding of numbers above their knower-level, whereas 2-knowers do. As researchers move to administering assessments remotely, the Point-to-X task promises to be an easy-to-administer alternative to Give-N for measuring children's emerging number knowledge and capturing nuances in children's number-word knowledge that Give-N may miss.

The Quality of Mother-Toddler Communication Predicts Language and Early Literacy in Mexican-American Children from Low-Income Households.

This longitudinal study documents the key role of early joint engagement in the language and early literacy development of Mexican-American children from low-income households. This rapidly growing population often faces challenges as sequential Spanish-English language learners. Videos of 121 mothers and their 2.5-year-old children interacting in Spanish for 15 min were recorded in 2009-2011 in the Dallas-Fort Worth metropolitan area. Researchers reliably rated general dyadic features of joint engagement-symbol-infused joint engagement, shared routines and rituals, and fluency and connectedness-that have been found to facilitate language development in young English-speaking children. The construct respeto, a valued aspect of traditional Latino parenting, was also rated using two culturally specific items-the parent's calm authority and the child's affiliative obedience. In addition, three individual contributions-maternal sensitivity, quality of maternal language input, and quality of child language production-were assessed. General features of joint engagement at 2.5 years predicted expressive and receptive language at 3.6 years and receptive language and early literacy at 7.3 years, accounting for unique variance over and above individual contributions at 2.5 years, with some effects being stronger in girls than boys. The level of culturally specific joint engagement did not alter predictions made by general features of joint engagement. These findings highlight the importance of the quality of early communication for language and literacy success of Mexican-American children from low-income households and demonstrate that culturally specific aspects of early interactions can align well with general features of joint engagement.