Emotional Availability (EA), the synchrony between parents and children's affective and behavioral states, is grounded in children's developmental abilities. Young children use motor behaviors to communicate their wants and needs and parents use these observable motor behaviors to guide their interaction behaviors. As development becomes more advanced, children and parents are able to interact with one another in new and more complex ways, thus fostering global development. The proposed study builds on EA research in children with typical development which highlights that children's linear change in EA over young childhood is mediated by developmental abilities and that social adversities present challenges to adult and child EA. EA predicts adaptive development, moderates adverse developmental outcomes in the presence of early adverse life experiences, and guides intervention aimed at optimizing parents and children's health and well-being. Evidence of EA in clinical populations is very scarce, with available studies having limitations in methodology and findings are not yet replicated. Early intervention rehabilitation professionals working with children with developmental delays often lack the training, resources, and support to assess and target EA as part of their standard of care. The objective of this study is to advance the body of knowledge on the impact of motor skills on the development of EA in young children with diverse motor abilities. Identifying delayed motor skills as a risk factor for EA will highlight the need to assess and target EA as part of early intervention. Results from this study will support the applicants long term career goals of creating research which optimizes children's development, familial well-being and early intervention efficacy. The proposed study is a secondary analysis and enhancement of prior collected data and includes 134 children with motor delays (7-16 months at baseline) and 37 children with typical motor development (5-7 months at baseline) enrolled at the emergence of sitting. Aim 1 will quantify the impact of motor skills on adult and child EA interaction behaviors. Aim 2 will compare the impact of age vs. motor skills on EA in skill matched participants. Aim 3 will identify the predictive relationship between baseline EA and the trajectory of children's motor development over 12 months. Post-hoc analyses of each aim will describe the findings within the context of children's gender, socio-economic status and race. Findings will provide foundational knowledge on constructs and behaviors which foster or impede development of EA. This knowledge will be immediately informative in guiding therapists' decision-making in practice and will inform future studies on developing clinically applicable assessment tools and designing clinical trials that target EA as a pathway to enhance program efficacy. The fellowship proposal offers the applicant training opportunities to execute a research study as princi...