PROJECT SUMMARY/ABSTRACT Attention selects which aspects of sensory input receive cognitive processing and thereby influence behavior. Drug addiction alters the attentional system, resulting in prominent attentional biases towards drug cues. Such drug-related attentional biases are related to the broader phenomenology of addiction, including craving and relapse. There has been long-standing interest in implementing attentional bias measures in clinical settings, either as a predictive measure to inform treatment decisions or as a target of treatment. However, a major barrier to the realization of this goal is that current means of assessing these biases are not sufficiently precise to support clinical utility, which has stifled progress in this area. Mirroring this complexity, and underscoring the need for clarity, debate has arisen concerning the role of learning history in the guidance of attention more broadly. Persistent attentional biases have been linked to reward history, learning from aversive outcomes, and outcome-independent selection history (e.g., familiarity). Emerging accounts of such experience-dependent attentional biases disagree about the nature of the underlying mechanism(s) involved. Without a solid understanding of the variety of influences of learning history on attention at a fundamental level, it will be difficult to understand how these influences contribute to addiction-related attentional biases. The research supported by the parent grant seeks to directly address this need by identifying, isolating, and measuring multiple hypothesized components of the attentional biases that characterize addiction, providing the precision necessary for more accurate predictions of patient outcomes and more targeted efforts to improve these outcomes through attentional bias modification. The proposed research supplement to support diversity in health-related research will expand upon the research proposed as a part of the parent grant, probing the mechanisms by which the exertion of physical effort modulates the control of attention and how different mechanisms of attentional learning are modulated by expectancies concerning effort expenditure, which together with the parent grant will provide a comprehensive picture of the multifaceted nature of experience-dependent attention. The overarching goal of the proposed research is to characterize multiple distinct components of experience-dependent attentional bias that contribute to attentional biases evident in drug-dependent individuals. These fundamental components of attentional bias will provide a much more precise window into the attentional processes that are relevant to the understanding of addiction than existing measures can offer. It is anticipated that the knowledge gained from the proposed research will provide a foundation for overcoming fundamental limitations in the clinical utility of attentional bias measures, allowing for fruitful exploration of this aspect of addiction...