PROJECT SUMMARY It is estimated that 36 million adults in the United States struggle with basic literacy skills. Deficient literacy skills have costly societal, economic, and individual implications (e.g., higher crime and unemployment rates; lower health and computer literacy skills). Yet, there is a paucity of rigorous research to understand these adults' underlying reading processes and an over-reliance on reading models and assessments developed for children in adult literacy programs. Recent evidence suggests that morphological awareness (MA), an understanding of the smallest units of meaning (i.e., prefixes), is an important contributor to the reading comprehension (RC) skills of struggling adult readers. MA remains uniquely predictive of RC controlling for prominent component skills from the Simple View of Reading (SVR) framework, including decoding and oral vocabulary. However, MA has been assessed for struggling adult and child readers using several experimental measures. Recent work with struggling adult readers and adolescent readers has assessed the dimensionality of the MA construct, with a lack of consensus as to what aspects of MA contribute to the multidimensionality. Emerging work with adolescents suggests that MA is best represented as a general factor (integrating overlap in shared variance among different MA measures) as well as specific factors (unique variance accounted for by task-, item-and person-specific aspects of MA). In addition, the general MA factor and the specific factors have exhibited differential relations with RC. Given the noted importance of MA to the RC skills of struggling adult readers, these findings suggest the need to better understand the construct validity of MA to develop better and more sensitive MA measures and to place MA in a larger model of RC. Thus, the aims of this project are twofold: a. to examine the psychometric properties of MA measures and dimensionality of the MA construct in order to refine and create a new MA battery for struggling adult readers; and b. to integrate MA within the SVR framework, examine its relations to RC, and to compare whether the relations among MA and known correlates to RC are equivalent between more-skilled (college students) and less-skilled, struggling adult readers. Meta-analyses in the children's literature suggest that MA interventions build vocabulary, decoding, and RC skills. Intervention work with struggling adult readers has focused primarily on decoding, phonics, and fluency, and produced minimal to no gains. Thus, it is imperative to build valid assessments to explore additional, malleable skills (i.e., MA) for future intervention work with this population.