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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., (© 2024 International Congress of Infant Studies.)

In his target article, Yarkoni prescribes descriptive research as a potential antidote for the generalizability crisis. In our commentary, we offer four guiding principles for conducting descriptive research that is generalizable and enduring: (1) prioritize context over control; (2) let naturalistic observations contextualize structured tasks; (3) operationalize the target phenomena rigorously and transparently; and (4) attend to individual data.

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.

Skilled object retrieval requires coordination of the perceptual and motor systems. Coordination is especially challenging when body position is changing and visual search is required to locate the target. In three experiments, we used a "pivot paradigm" to induce changes in body position: Participants were passively pivoted 180° toward a target placed at varied locations to the left and right of the center of a reaching board. Experiment 1 showed that 6- to 15-month-old infants (n = 41) plan prehension so quickly that they retrieve targets mid-turn and scale their reaches to target location relative to turn direction. Experiment 2 characterized planning mid-turn reaching in 6- to 8-month-olds (n = 5) wearing a head-mounted eye tracker. Reach planning depended on when the target appeared in the field of view-not on target fixation. Experiment 3 used head-mounted eye tracking and motion tracking to assess perceptual-motor coordination in adults (n = 13). Adults displayed more mid-turn reaching than infants. But like infants, adults scaled reaching to target location relative to turn direction, and contact time depended on when the target came into view-not on target fixation. Findings show that fast, efficient perceptual-motor coordination supports flexibility in infant prehension, and constraints on coordination are similar across the lifespan., (© 2019 Wiley Periodicals, Inc.)

Multisensory attention skills provide a crucial foundation for early cognitive, social, and language development, yet there are no fine-grained, individual difference measures of these skills appropriate for preverbal children. The Multisensory Attention Assessment Protocol (MAAP) fills this need. In a single video-based protocol requiring no language skills, the MAAP assesses individual differences in three fundamental building blocks of attention to multisensory events-the duration of attention maintenance, the accuracy of intersensory (audiovisual) matching, and the speed of shifting-for both social and nonsocial events, in the context of high and low competing visual stimulation. In Experiment 1, 2- to 5-year-old children (N = 36) received the MAAP and assessments of language and cognitive functioning. In Experiment 2 the procedure was streamlined and presented to 12-month-olds (N = 48). Both infants and children showed high levels of attention maintenance to social and nonsocial events, impaired attention maintenance and speed of shifting when competing stimulation was high, and significant intersensory matching. Children showed longer maintenance, faster shifting, and less impairment from competing stimulation than infants. In 2- to 5-year-old children, duration and accuracy were intercorrelated, showed increases with age, and predicted cognitive and language functioning. The MAAP opens the door to assessing developmental pathways between early attention patterns to audiovisual events and language, cognitive, and social development. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Detecting intersensory redundancy guides cognitive, social, and language development. Yet, researchers lack fine-grained, individual difference measures needed for studying how early intersensory skills lead to later outcomes. The intersensory processing efficiency protocol (IPEP) addresses this need. Across a number of brief trials, participants must find a sound-synchronized visual target event (social, nonsocial) amid five visual distractor events, simulating the "noisiness" of natural environments. Sixty-four 3- to 5-year-old children were tested using remote eye-tracking. Children showed intersensory processing by attending to the sound-synchronous event more frequently and longer than in a silent visual control, and more frequently than expected by chance. The IPEP provides a fine-grained, nonverbal method for characterizing individual differences in intersensory processing appropriate for infants and children. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

What do infants learn when they learn to sit upright? We tested behavioral flexibility in learning to sit-the ability to adapt posture to changes in the environment-in 6- to 9-month-old infants sitting on forward and backward slopes. Infants began with slant at 0°; then slant increased in 2° increments until infants lost balance. Infants kept balance on impressively steep slopes, especially in the forward direction, despite the unexpected movements of the apparatus. Between slant adjustments while the slope was stationary, infants adapted posture to the direction and degree of slant by leaning backward on forward slopes and forward on backward slopes. Postural adaptations were nearly optimal for backward slopes. Sitting experience predicted greater postural adaptations and increased ability to keep balance on steeper changes of slant, but only for forward slopes. We suggest that behavioral flexibility is integral to learning to sit and increases with sitting experience., (© 2017 Wiley Periodicals, Inc.)

Traditionally, crawling and sitting are considered distinct motor behaviors with different postures and functions. Ten- to 12-month-old infants were observed in the laboratory or in their homes while being coaxed to crawl continuously over long, straight walkways (Study 1; N = 20) and during spontaneous crawling during free play (Study 2; N = 20). In every context, infants stopped crawling to sit 3-6 times per minute. Transitions from crawling to sitting frequently turned infants' bodies away from the direction of heading; subsequent transitions back to crawling were offset by as much as 180° from the original direction of heading. Apparently, body reorientations result from the biomechanics of transitioning between crawling and sitting. Findings indicate that sustained, linear crawling is likely an epiphenomenon of how gait is studied in standard paradigms. Postural transitions between crawling and sitting are ubiquitous and can represent a functional unit of action. These transitions and the accompanying body reorientations likely have cascading effects for infants' exploration, visual perception, and spatial cognition., (© 2014 John Wiley & Sons Ltd.)

Recent research has revealed the important role of multimodal object exploration in infants' cognitive and social development. Yet, the real time effects of postural position on infants' object exploration have been largely ignored. In the current study, 5- to 7-month-old infants ( N = 29) handled objects while placed in supported sitting, supine, and prone postures, and their spontaneous exploratory behaviors were observed. Infants produced more manual, oral, and visual exploration in sitting compared to lying supine and prone. Moreover, while sitting, infants more often coupled manual exploration with mouthing and visual examination. Infants' opportunities for learning from object exploration are embedded within a real time postural context that constrains the quantity and quality of exploratory behavior.

This study examined reaching in 6-, 8-, and 10-month-olds during binocular and monocular viewing in a dynamic reaching situation. Infants were rotated toward a flat vertical board and reached for objects at one of seven positions along a horizontal line at shoulder height. Hand selection, time to contact the object, and reaching accuracy were examined in both viewing conditions. Hand selection was strongly dependent on object location, not on infants' age or whether one eye was covered. Monocular viewing and age did, however, affect time to object contact and contact errors: Infants showed longer contact times when one eye was covered, and 6-month-olds made more contact errors in the monocular condition. For right-hand selection, contact times were longer when the covered right eye was leading during the chair rotation. For left-hand selection, there were no differences in contact time due to whether the covered eye was leading during rotation.

Three-dimensional (3D) object completion, the ability to perceive the backs of objects seen from a single viewpoint, emerges at around 6 months of age. Yet, only relatively simple 3D objects have been used in assessing its development. The present study examined infants' 3D object completion when presented with more complex stimuli. Infants ( N = 48) were habituated to an "L"-shaped object shown from a limited viewpoint; then they were tested with volumetrically complete (solid) and incomplete (hollow) versions of the object. Four-month-olds and 6-month-old girls had no preference for either display. Six-month-old boys and both sexes at 9.5 months of age showed a novelty preference for the incomplete object. A control group ( N = 48), only shown the test displays, had no spontaneous preference. Perceptual completion of complex 3D objects requires infants to integrate multiple, local object features and thus may tax their nascent attentional skills. Infants might use mental rotation to supplement performance, giving an advantage to young boys. Examining the development of perceptual completion of more complex 3D objects reveals distinct mechanisms for the acquisition and refinement of 3D object completion in infancy.

Motor overflow is extraneous movement in a limb not involved in a motor action. Typically, overflow is observed in people with neurological impairments and in healthy children and adults during strenuous and attention-demanding tasks. In the current study, we found that young infants produce vast amounts of motor overflow, corroborating claims of symmetry being the default state of the motor system. While manipulating an object with one hand, all 27 of the typically developing 4.5- to 7.5-month-old infants who we observed displayed overflow movements of the free hand (on 4/5 of unimanual actions). Mirror-image movements of the hands occurred on 1/8 of unimanual actions, and the hands and legs moved in synchrony on 1/3 of unimanual acts. Motor overflow was less frequent when infants were in a sitting posture and when infants watched their acting hand, suggesting that upright posture and visual examination may help to alleviate overflow and break obligatory symmetry in healthy infants., (Copyright © 2011 Wiley Periodicals, Inc.)

Despite hundreds of studies describing infants' visual exploration of experimental stimuli, researchers know little about where infants look during everyday interactions. The current study describes the first method for studying visual behavior during natural interactions in mobile infants. Six 14-month-old infants wore a head-mounted eye-tracker that recorded gaze during free play with mothers. Results revealed that infants' visual exploration is opportunistic and depends on the availability of information and the constraints of infants' own bodies. Looks to mothers' faces were rare following infant-directed utterances but more likely if mothers were sitting at infants' eye level. Gaze toward the destination of infants' hand movements was common during manual actions and crawling, but looks toward obstacles during leg movements were less frequent., (© 2011 The Authors. Child Development © 2011 Society for Research in Child Development, Inc.)

How do infants learn to perceive the backs of objects that they see only from a limited viewpoint? Infants' 3-dimensional object completion abilities emerge in conjunction with developing motor skills--independent sitting and visual-manual exploration. Infants at 4.5 to 7.5 months of age (n = 28) were habituated to a limited-view object and tested with volumetrically complete and incomplete (hollow) versions of the same object. Parents reported infants' sitting experience, and infants' visual-manual exploration of objects was observed in a structured play session. Infants' self-sitting experience and visual-manual exploratory skills predicted looking at the novel, incomplete object on the habituation task. Further analyses revealed that self-sitting facilitated infants' visual inspection of objects while they manipulated them. The results are framed within a developmental systems approach, wherein infants' sitting skill, multimodal object exploration, and object knowledge are linked in developmental time., (Copyright 2009 APA, all rights reserved.)

Three-dimensional (3D) object completion was investigated by habituating 4- and 6-month-old infants (n= 24 total) with a computer-generated wedge stimulus that pivoted 15 degrees , providing only a limited view. Two displays, rotating 360 degrees , were then shown: a complete, solid volume and an incomplete, hollow form composed only of the sides seen during habituation. There were no reliable preferences for either test display by 4-month-olds. At 6 months, infants showed a reliable novelty preference for the incomplete test display. Infants in a control group (n= 24) not habituated to the limited-view wedge preferred neither test display. By 6 months, infants may represent simple objects as complete in 3D space despite a limited perspective. Possible mechanisms of development of 3D object completion are discussed.