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.

"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.

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.

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.

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.

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.

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.

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.

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.

Children's use of everyday artifacts: Learning the hidden affordance of zipping.

The everyday world is populated with artifacts that require specific motor actions to use objects as their designers intended. But researchers know little about how children learn to use everyday artifacts. We encouraged forty-four 12- to 60-month-old children to unzip a vinyl pouch during a single 60-s trial. Although unzipping a pouch may seem simple, it is not. Unzipping requires precise role-differentiated bimanual actions-one hand must stabilize the pouch while the other hand applies a pulling force on the tab. Moreover, kinematic data from six adults showed that the tolerance limits for applying the forces are relatively narrow (pulling the tab within 63° of the zipper teeth while stabilizing the pouch within 4 cm of the slider). Children showed an age-related progression for the unzipping action. The youngest children did not display the designed pulling action; children at intermediate ages pulled the tab but applied forces outside the tolerance limits (pulled in the wrong direction, failed to stabilize the pouch in the correct location), and the oldest children successfully implemented the designed action. Findings highlight the perceptual-motor requirements in children's discovery and implementation of the hidden affordances of everyday artifacts.

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.

Mothers' distancing language relates to young children's math and literacy skills.

Parents' distancing language-language that requires cognitive abstraction and moves beyond the "here and now"-relates to children's literacy skills, but its association with mathematics remains unexamined. Participants were 242 mother-child dyads from African American, Chinese American, Dominican American, and Mexican American backgrounds. Mothers' distancing language was examined while mothers shared a wordless book with their 5-year-olds; children's math and literacy skills were assessed when children were 5.0 and 6.5 years of age. Mothers' distancing language, but not amount of language (word tokens), related to children's concurrent math and literacy skills. Mothers' distancing language predicted growth in children's literacy skills over time and related to later math indirectly through associations with early math. The importance of distancing language for cognitive growth may have implications for parenting and classroom practice.

Play in Mexican-American mothers and toddlers is frequent, multimodal, and rich in symbolic content.

Play offers rich opportunities for toddlers to develop motor, social, cognitive, and language skills, particularly during interactions with adult caregivers who may scaffold toddlers to higher levels of play than toddlers achieve on their own. However, research on play has narrowly focused on children from White, middle-income backgrounds, leaving a dearth of knowledge about dyadic play in diverse cultural communities. We videorecorded 222 Mexican-American mothers playing with their 2-year-old toddlers with a standard set of toys. Play behaviors were coded as nonsymbolic or symbolic (play type) and as expressed through manual, verbal, or multiple channels (play modality). Play between toddlers and mothers was frequent, high in symbolic content, and toddler play closely corresponded with mother play in type and modality: Toddlers' nonsymbolic play related to mothers' nonsymbolic play; toddlers' symbolic play related to mothers' symbolic play; toddlers' manual play related to mothers' manual play; and toddlers' multimodal play related to mothers' multimodal play. Play in Mexican-American mothers and toddlers is frequent, multimodal, and symbolically rich, offering new directions for future research and practice.

Missing in action: Tool use is action based.

In this commentary on Osiurak and Reynaud's target article, we argue that action is largely missing in their account of the ascendance of human technological culture. We propose that an action-based developmental account can help to bridge the cognitive-sociocultural divide in explanations of the discovery, production, and cultural transmission of human tool use.

Do, say, learn: the functions of mothers' speech to infants.

We examined the functions of mothers' speech to infants during two tasks - book-sharing and bead-stringing - in low-income, ethnically diverse families. Mexican, Dominican, and African American mothers and their infants were video-recorded sharing wordless books and toy beads in the home when infants were aged 1;2 and 2;0. Mothers' utterances were classified into seven categories (labels/descriptions, emotion/state language, attention directives, action directives, prohibitions, questions, and vocal elicitations) which were grouped into three broad language functions: referential language, regulatory language, and vocalization prompts. Mothers' ethnicity, years of education, years living in the United States, and infant sex and age related to mothers' language functions. Dominican and Mexican mothers were more likely to use regulatory language than were African American mothers, and African American mothers were more likely to use vocalization prompts than were Latina mothers. Vocalization prompts and referential language increased with mothers' education and Latina mothers' years living in the United States. Finally, mothers of boys used more regulatory language than did mothers of girls. Socio-cultural and developmental contexts shape the pragmatics of mothers' language to infants.

Routine Language: Speech Directed to Infants During Home Activities.

Everyday activities are replete with contextual cues for infants to exploit in the service of learning words. Nelson's (1985) script theory guided the hypothesis that infants participate in a set of predictable activities over the course of a day that provide them with opportunities to hear unique language functions and forms. Mothers and their firstborn 13-month-old infants (N = 40) were video-recorded during everyday activities at home. Transcriptions and coding of mothers' speech to infants-time-locked to activities of feeding, grooming, booksharing, object play, and transition-revealed that the amount, diversity, pragmatic functions, and semantic content of maternal language systematically differed by activity. The activities of everyday life shape language inputs to infants in ways that highlight word meaning.

Language Matters: Denying the Existence of the 30-Million-Word Gap Has Serious Consequences.

Sperry, Sperry, and Miller (2018) aim to debunk what is called the 30-million-word gap by claiming that children from lower income households hear more speech than Hart and Risley () reported. We address why the 30-million-word gap should not be abandoned, and the importance of retaining focus on the vital ingredient to language learning-quality speech directed to children rather than overheard speech, the focus of Sperry et al.'s argument. Three issues are addressed: Whether there is a language gap; the characteristics of speech that promote language development; and the importance of language in school achievement. There are serious risks to claims that low-income children, on average, hear sufficient, high-quality language relative to peers from higher income homes.

The Roles of Self-Socialization and Parent Socialization in Toddlers' Gender-Typed Appearance.

Children's gender-stereotypical dress and appearance might be one of the first representations of children's emerging sense of gender identity. Gender self-socialization theories posit that as children become more aware of gender categories, they become motivated to adhere to gender stereotypes, such as by expressing interest in dressing in feminine or masculine ways. Socialization theories predict that children's gender-typed appearance reflects parents' choices. For example, gender-traditional parents might dress their children in gender-stereotypical ways. At the same time, dressing in gender-stereotypical ways might contribute to children's growing awareness of gender categories. The current study investigated the factors associated with gender-typed appearance among 175 (87 girls, 88 boys) Mexican American, Dominican American, and African American 2-year-olds. We examined both child and parent contributions to early gender-typed appearance. To measure children's early conceptual understanding of gender categories, we assessed children's use and recognition of gender verbal labels. To examine the influence of parent socialization, we assessed mothers' gender-role attitudes. Children's gender-typed appearance was observed and coded during an assessment. Surprisingly, mothers' gender-role attitudes were not significantly associated with toddlers' gender-typed appearance. However, toddlers' gender labeling was associated with their gender-typed appearance, suggesting that self-socialization processes can be found as early as 24 months of age.

Power in methods: language to infants in structured and naturalistic contexts.

Methods can powerfully affect conclusions about infant experiences and learning. Data from naturalistic observations may paint a very different picture of learning and development from those based on structured tasks, as illustrated in studies of infant walking, object permanence, intention understanding, and so forth. Using language as a model system, we compared the speech of 40 mothers to their 13-month-old infants during structured play and naturalistic home routines. The contrasting methods yielded unique portrayals of infant language experiences, while simultaneously underscoring cross-situational correspondence at an individual level. Infants experienced substantially more total words and different words per minute during structured play than they did during naturalistic routines. Language input during structured play was consistently dense from minute to minute, whereas language during naturalistic routines showed striking fluctuations interspersed with silence. Despite these differences, infants' language experiences during structured play mirrored the peak language interactions infants experienced during naturalistic routines, and correlations between language inputs in the two conditions were strong. The implications of developmental methods for documenting the nature of experiences and individual differences are discussed.

Immigrant Chinese Mothers' Socialization of Achievement in Children: A Strategic Adaptation to the Host Society.

Academic socialization by low-income immigrant mothers from Mainland China was investigated in two studies. Immigrant Chinese mothers of first graders (n = 52; Mage  = 38.69) in the United States (Study 1) and kindergartners (n = 86; Mage  = 36.81) in Hong Kong (Study 2) tell stories that emphasized achieving the best grade through effort more than did African American (n = 39; Mage  = 31.44) and native Hong Kong (n = 76; Mage  = 36.64) mothers, respectively. The emphasis on achievement was associated with mothers' heightened discussion on discrimination (Study 1) and beliefs that education promotes upward mobility (Study 2), as well as children's expectations that a story protagonist would receive maternal criticism for being nonpersistent in learning (Study 2).