ABSTRACT Young adults’ heavy drinking represents a substantial public health problem, in part because alcohol use is associated with risk behaviors that can have both short- and long-term consequences for individuals and society as a whole. Alcohol myopia theory (AMT) has emerged as a prominent framework to understand why acute alcohol intoxication is associated with increased likelihood of risk behaviors, such as aggression, unprotected sex, and unsafe driving. AMT asserts that alcohol narrows one’s attention, reducing the range of external and internal cues that one can process, increasing the focus on “here-and-now” central information at the cost of longer-term, peripheral information. This attentional narrowing is theorized to limit the processing of cues that may otherwise inhibit risk behaviors, as costs and consequences tend to be more peripheral or temporally distant than immediate rewards. Although AMT is supported by laboratory research, the connection between AMT and real-world risk-taking remains unclear. Clarifying whether myopia is indeed a mechanism will be an important step toward dynamic theory-based interventions targeting alcohol-related risk behaviors. To advance theory and inform intervention development, the current study will (1) adapt laboratory-based cognitive tasks to assess spatial and temporal alcohol myopia for smartphone-based ecological momentary assessments (EMA), (2) evaluate feasibility, acceptability, reliability, and validity of the adapted smartphone tasks in laboratory and EMA settings, and (3) explore AMT within EMA by testing myopia as a mediator of the intoxication-risk behavior association. To achieve these aims, interviews will be conducted with up to 30 young adults to inform iterative improvements that maximize usability of myopia tasks on smartphones. Then, 100 heavy drinking young adults will complete a laboratory session involving alcohol administration to test the adapted myopia tasks within a controlled setting. These participants will also complete eight consecutive weekends of EMA to assess spatial and temporal myopia and risk behaviors in their natural environments, while wearing a wrist-based transdermal alcohol biosensor to objectively and unobtrusively assess intoxication levels. By integrating laboratory and EMA findings, this study will yield tasks that allow for a comprehensive understanding of alcohol myopia, including within- and between-person variability in myopia, dose-dependent effects of AMT within natural drinking episodes, and associations with real-world risk behaviors. The rigorous development and testing of cognitive EMA for myopia will pave the way for new just-in-time adaptive interventions targeting myopia to reduce risk behaviors when drinking. By using innovative tools and methodologies to advance behavioral research and interventions, this proposal is consistent with the NIAAA mission and strategic goals to identify patterns and strategies to prevent alcohol-related con...