Increased survival rates of medically fragile infants lead to an increased number of children with functional impairments later in life. There is a critical need for clinical tools that can provide non- invasive monitoring of these at-risk infantsin their natural settings and early detection of motor delays and impairments. Early detection of delay or impairment provides the opportunity for early treatment which improves health outcomes for them over the lifespan. Motor development can be evaluated by studying infant play behavior and interactions with toys. As such, our long-term goal is to develop an advanced play environment, SmarToyGym, through which we can objectively assess the motor development of at-risk infants and quantify the effects of future interventions. Our working hypothesis is that metrics derived from measuring body and arm/hand movements while infants play within this environment will identify infants with atypical motor behavior. Our first specific aim is to develop a SmarToyGym where sensorized, wireless toys are strategically hung and placed within reach of infants to elicit toy-oriented body and arm/hand movements. Each toy will be equipped with sensors capable of measuring the infant's grasping actions such as squeezing, pinching, and shaking/tilting. A low-cost 3D motion capture system will be used to collect video data and the infants' reaching and body kinematics in response to the toys. A pressure mat will be used to measure postural changes to detect weight shifts, rolling, crawling and other movements away from the initial posture. Our second specific aim is to conduct proof-of-concept testing of the SmarToyGym with atypical and typical developing infants. We will include 24 infants ages 3 to 11 months who are categorized as high-risk or low-risk using the Bayley Infant Neurodevelopmental Screener (BINS) discriminative tool. Inclusion criteria for atypical infants will be motor impairment and/or cognitive impairment as defined by sub-scores on Bayley Scale of Infant Development (BSID-III) evaluation tool. Twelve atypical and 12 typical infants will be observed playing within SmarToyGym with and without toys for 5 consecutive days. Using this study, we will 1) identify a battery of metrics that are able to discriminate between atypical and typical infants, 2) determine the reliability/reproducibility of the measurements, and 3) determine the best clustering of the most sensitive metrics into an easy to use home screening methodology. Results from this R21 will inform the design of a larger trial to refine the tool and explore the potential for expanding the tool for treatment applications. The potential impact of our work is world-wide and can alter the lives of thousands of children through earlier intervention and better long-term functional outcomes.