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

Early word learning is influenced by physical environments

During word learning moments, toddlers experience labels and objects in particular environments. Do toddlers learn words better when the physical environment creates contrasts between objects with different labels? Thirty-six 21- to 24-month-olds (92% White, 22 female, data collected 8/21-4/22) learned novel words for novel objects presented using an apparatus that mimicked a shape-sorter toy. The manipulation concerned whether or not the physical features of the environments in which objects occurred heightened the contrasts between the objects. Toddlers only learned labels for objects presented in environments where the apparatus heightened the contrast between the objects (b = .068). These results emphasize the importance of investigating word learning in physical environments that more closely approximate young children's everyday experiences with objects.

Infant-directed communication: Examining the many dimensions of everyday caregiver-infant interactions

Everyday caregiver-infant interactions are dynamic and multidimensional. However, existing research underestimates the dimensionality of infants' experiences, often focusing on one or two communicative signals (e.g., speech alone, or speech and gesture together). Here, we introduce "infant-directed communication" (IDC): the suite of communicative signals from caregivers to infants including speech, action, gesture, emotion, and touch. We recorded 10 min of at-home play between 44 caregivers and their 18- to 24-month-old infants from predominantly white, middle-class, English-speaking families in the United States. Interactions were coded for five dimensions of IDC as well as infants' gestures and vocalizations. Most caregivers used all five dimensions of IDC throughout the interaction, and these dimensions frequently overlapped. For example, over 60% of the speech that infants heard was accompanied by one or more non-verbal communicative cues. However, we saw marked variation across caregivers in their use of IDC, likely reflecting tailored communication to the behaviors and abilities of their infant. Moreover, caregivers systematically increased the dimensionality of IDC, using more overlapping cues in response to infant gestures and vocalizations, and more IDC with infants who had smaller vocabularies. Understanding how and when caregivers use all five signals-together and separately-in interactions with infants has the potential to redefine how developmental scientists conceive of infants' communicative environments, and enhance our understanding of the relations between caregiver input and early learning. RESEARCH HIGHLIGHTS: Infants' everyday interactions with caregivers are dynamic and multimodal, but existing research has underestimated the multidimensionality (i.e., the diversity of simultaneously occurring communicative cues) inherent in infant-directed communication. Over 60% of the speech that infants encounter during at-home, free play interactions overlap with one or more of a variety of non-speech communicative cues. The multidimensionality of caregivers' communicative cues increases in response to infants' gestures and vocalizations, providing new information about how infants' own behaviors shape their input. These findings emphasize the importance of understanding how caregivers use a diverse set of communicative behaviors-both separately and together-during everyday interactions with infants.

Referent-oriented interactions in infancy: A naturalistic, longitudinal case study from an English-speaking household

Caregivers use a of combination labeling, pointing, object grasping, and gaze to communicate with infants about referents in their environment. By two years of age, children reliably use these referent-oriented cues to communicate and learn. While there is some evidence from lab-based studies that younger infants attend to and use referent-oriented cues during communication, some more naturalistic studies have found that in the first year of life, infants do not robustly leverage these cues during dyadic interactions. The current study examined parent and infant gaze, touching, pointing, and reaching to referents for a wide range of nouns, verbs, adjectives, and other early-learned words during 59 one-hour head-camera recordings sampled from one English-learning infants' life between 6 and 12 months of age. We found substantial variability across individual words for all cues. Some variability was explained by referent concreteness and the grammatical category of the label. The parent's touching of labeled referents increased across months, suggesting that parent-infant-referent interactions may change with development. Future studies should investigate the trajectories of specific types of words and contexts, rather than attempting to discover possibly non-existent universal trajectories of parent and infant referent-oriented behaviors.

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.

"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.

Towards imaging the infant brain at play

Infants' first-person experiences are crucial to early cognitive and neural development. To a vast extent, these early experiences involve play, which in infancy takes the form of object exploration. While at the behavioral level infant play has been studied both using specific tasks and in naturalistic scenarios, the neural correlates of object exploration have largely been studied in highly controlled task settings. These neuroimaging studies did not tap into the complexities of everyday play and what makes object exploration so important for development. Here, we review selected infant neuroimaging studies, spanning from typical, highly controlled screen-based studies on object perception to more naturalistic designs and argue for the importance of studying the neural correlates of key behaviors such as object exploration and language comprehension in naturalistic settings. We suggest that the advances in technology and analytic approaches allow measuring the infant brain at play with the use of functional near-infrared spectroscopy (fNIRS). Naturalistic fNIRS studies offer a new and exciting avenue to studying infant neurocognitive development in a way that will draw us away from our laboratory constructs and into an infant's everyday experiences that support their development.

The road to conventional tool use: Developmental changes in children's material engagement with artifacts in nursery school

The development of tool use in early childhood is a topic of continuing interest in developmental psychology. However, the lack of studies in ecological settings results in many unknowns about how children come to use artifacts according to their cultural function. We report a longitudinal study with 17 sociodemographically diverse children (8 female) attending a nursery school in Madrid (Spain) and their two adult female teachers. Using mixed-effects models and Granger causality analysis, we measured changes in the frequency and duration of children's object uses between 7 and 17 months of age and in the directional influences among pairs of behaviors performed by teachers and children. Results show a clear shift in how children use artifacts. As early as 12 months of age, the frequency of conventional uses outweighs that of all other types of object use. In addition, object uses become shorter in duration with age, irrespective of their type. Moreover, certain teachers' nonlinguistic communicative strategies (e.g., demonstrations of canonical use and placing gestures) significantly influence and promote children's conventional tool use. Findings shed light on how children become increasingly proficient in conventional tool use through interactions with artifacts and others in nursery school.

Autism: The face value of eye contact

Inattention to faces in clinical assessments is a robust marker for autism. However, a new study distinguishes diagnostic marker from behavioral mechanism, showing that face looking in everyday activity is equally rare in autistic and neurotypical children and not required for joint attention in either group.

Infants exploring objects: A cascades perspective

Infants spend much of their time exploring objects (Herzberg et al., 2021), and object exploration is linked to learning and development in various domains (e.g., social, cognitive, motor). But how does exploration develop in the first place, and how, exactly, does exploration promote learning? One way to approach these process-oriented questions is with a developmental cascades perspective, which holds that new skills emerge from earlier-developing ones and that various interactions with people and objects accumulate over time to influence multiple domains of development (Masten & Cicchetti, 2010). In this chapter, we describe object exploration from a developmental cascades perspective. In Section 2, we describe typical and atypical trajectories of exploration behaviors, noting how these behaviors emerge from earlier-developing cognitive and motor skills. In Section 3, we discuss how object exploration opens the door for new types of learning opportunities. In Section 4, we discuss early experiences that may shape the development of object exploration. Altogether, we aim to convey that new developments in exploration skills are extensions of earlier-developing skills, and that seemingly insignificant exploratory behaviors (e.g., shaking a rattle) may result in numerous and varied consequences for the developing infant.