MiDiario: Mobile Intervention for Diabetes via Reflection and Introspection in My Own Words - PROJECT SUMMARY/ABSTRACT Latino adolescents with Type 1 Diabetes (T1D) face substantial disparities in care and outcomes, making new tools to support this population essential. Managing T1D requires a complex set of knowledge and decision- making skills. Adolescents have specific challenges to managing T1D, including psychosocial needs for autonomy and fitting in with peers, along with still-developing decision-making and planning skills. Additionally, Latino adolescents face both unique challenges and a lack of access to culturally-sensitive care and support that recognizes the unique experiences, language, and barriers for these patients. Previous research in social psychology has demonstrated that counterfactual (“what if”) thinking paired with appropriate educational content can improve health outcomes. Convergently, innovative culturally sensitive approaches to diabetes care and patient education improve T1D outcomes for Latino adolescents. Although numerous mobile applications (apps) exist for diabetes management, none currently offer a feature set targeted to this population that combines cutting-edge behavioral science on self-efficacy and behavior change with models of culturally appropriate care. Our preliminary studies demonstrate the impact of counterfactual reflection tasks on healthy eating intentions in Latinos, the effects of culture on counterfactual functionality, and the benefits of culturally-sensitive care to outcomes in Latino adolescents with T1D, offering proof-of-concept for the core assumptions of this product. In this Phase 1 SBIR, we will build a prototype of a new app that will help Latino adolescents manage their T1D by offering strengths-based, culturally sensitive tools to build knowledge and facilitate self-efficacy and planning. We will achieve this through two aims. Aim 1 will optimize the design of the app through end user research and internal testing. Aim 2 validate the acceptability and usability of the app. To do this, we will develop new reflection tasks to facilitate self-management and validate these tasks through mixed-methods research in patient populations. Additionally, we will test the usability and acceptability of a working prototype in the end user population through semi-structured interviews and quantitative measurement. By creating an innovative app to manage T1D, the planned research will offer advancements to the treatment of T1D in Latino adolescents. Additionally, the research will provide insights into how social cognitive science can be integrated into clinical practice to support patient efficacy in managing T1D. Beyond improving clinical care, the research will advance social cognitive psychology by investigating the functionality of counterfactual reflection and intention generation in a novel health domain. Together, these innovations will address a critical disparity in health to advance healthy living for Latino Americans as well as offering new tools for future innovations to reduce disparities in related domains.