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.

The world is filled with artifacts designed for intended actions and consequences. Think of children's interactions with toys (interlocking Lego bricks), food (peeling the foil on a yogurt container), toiletry items (pressing the pump of a hand lotion), household objects (twisting a faucet), and clothing (zipping, buttoning, snapping). Such designed actions are so deeply engrained in adults' activities of daily living that the perceptual-motor requirements seem intuitive. However, for children, it takes years before they learn the specific motor actions to operate everyday artifacts.Despite the prevalence of artifacts in children's everyday lives, researchers know little about how children learn designed actions.Previous work focused primarily on age norms for skill onset based on children's success using zippers, buttons, and so on (Folio & Fewell, 2000; Teaford, 2010), but developmental change in the perceptual-motor requirements remains uncharted. Consequently, researchers cannot know why implementing everyday artifacts takes years to learn; and parents, teachers, and occupational therapists must rely on artistry and common sense to help children perform activities of everyday living. In addition to age-related changes in success, task analyses of particular designed actions and detailed

Goal-directed actions involve problem solving-how to coordinate perception and action to get the job done. Whereas previous work focused on the ages at which children succeed in problem solving, we focused on how children solve motor problems in real time. We used object fitting as a model system to understand how perception and action unfold from moment to moment. Preschoolers (N=25) and adults (N=24) inserted 3D shapes into their corresponding openings in a "shape-sorting" box. We applied a new combination of real-time methods to the problem of object fitting-head-mounted eye tracking to record looking behaviors, video micro-coding to record adjustments in object orientation between reach and insertion, and real-time analysis techniques (recurrent quantification analysis and Granger causality) to test the timing relations between visual and manual actions. Children, like adults, solved the problem successfully. However, adults outperformed children in terms of their speed in fitting, and speed depended on when adjustments of object orientation occurred. Adults adjusted object orientation during transport, whereas children adjusted object orientation after arriving at the box. Children's delays in adjustment resulted from delays in looking at the target shape and its corresponding aperture. Findings show that planning is a real-time cascade of perception and action, and highlight looking as the basis for planning actions prospectively. We suggest that developmental improvements in problem solving are driven by real-time changes in the instigation of the planning cascade and the timing of its components.

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