Human interaction involves the organization of a collection ofsensorimotor systems across space and time. The study ofhow coordination develops in child-parent interaction hasprimarily focused on understanding the development ofspecific coordination patterns from individual modalities.However, less work has taken a systems view andinvestigated the development of coordination among multipleinterdependent behaviors. In the present work, we usedGranger causality as a mathematical model to constructdyadic causal networks of multimodal data collected from alongitudinal study of child-parent interaction. At a group-level, we observed increases in the number of causal links andin the strength of such links in dyadic interaction from 9-months to 12-months. At an individual-level, we observedhigh variability in the types of causal links that emergedacross developmental ages. We discuss these results in termsof a multicausality hypothesis for the development of humancoordination.

Sustained visual attention is crucial to many developmentaloutcomes. We demonstrate that, consistent with thedevelopmental systems view, sustained visual attentionemerges from and is tightly tied to sensory motor coordination.We examined whether changes in manual behavior altertoddlers’ eye gaze by giving one group of children heavy toysthat were hard to pick up, while giving another group ofchildren perceptually identical toys that were lighter, easy topick up and hold. We found a tight temporal coupling betweenthe dynamics of visual attention and the dynamics of manualactivities on objects, a relation that cannot be explained byinterest alone. In the Heavy condition, toddlers looked atobjects just as much as did toddlers in the Light condition butdid so through many brief glances, whereas in Light conditionlooks to the objects were longer and sustained. We discuss theimplication of hand-eye coordination in the development ofvisual attention.

Young children's visual environments are dynamic, changing moment-by-moment as children physically and visually explore spaces and objects and interact with people around them. Head-mounted eye tracking offers a unique opportunity to capture children's dynamic egocentric views and how they allocate visual attention within those views. This protocol provides guiding principles and practical recommendations for researchers using head-mounted eye trackers in both laboratory and more naturalistic settings. Head-mounted eye tracking complements other experimental methods by enhancing opportunities for data collection in more ecologically valid contexts through increased portability and freedom of head and body movements compared to screen-based eye tracking. This protocol can also be integrated with other technologies, such as motion tracking and heart-rate monitoring, to provide a high-density multimodal dataset for examining natural behavior, learning, and development than previously possible. This paper illustrates the types of data generated from head-mounted eye tracking in a study designed to investigate visual attention in one natural context for toddlers: free-flowing toy play with a parent. Successful use of this protocol will allow researchers to collect data that can be used to answer questions not only about visual attention, but also about a broad range of other perceptual, cognitive, and social skills and their development.

The ability to rapidly recognize words and link them to referents in context is central to children's early language development. This ability, often called word recognition in the developmental literature, is typically studied in the looking-while-listening paradigm, which measures infants' fixation on a target object (vs. a distractor) after hearing a target label. We present a large-scale, open database of infant and toddler eye-tracking data from looking-while-listening tasks. The goal of this effort is to address theoretical and methodological challenges in measuring vocabulary development. We present two analyses of the current database (N=1,320): (1) capturing age-related changes in infants' word recognition while generalizing across item-level variability and (2) assessing how a central methodological decision -- selecting the time window of analysis -- impacts the reliability of measurement. Future efforts will expand the scope of the current database to advance our understanding of participant-level and item-level variation in children's vocabulary development.