PROJECT SUMMARY About 60% of children can’t read proficiently, which is concerning as reading comprehension (RC) is linked to educational, vocational, and health outcomes. While a robust neurocognitive literature exists on word-level processes, a necessary but not sufficient skill for RC, similar studies at the discourse level (i.e., while reading passages/connected text) are largely absent in developing readers. This proposal tackles this needed research by systematically interrogating how adolescents’ neural variations during situation model formation (or building mental models while reading) results in RC success/failure. A critical consideration for such research is that texts are not monolithic, even though they are often treated as such: they vary by granular text features (e.g., word frequency) and by their superstructures, or whether a text is narrative (NarrT, stories) or expository (ExpT, informational text such as science passages). This is important, as ExpT is central for learning new material, while NarrT for socio-emotional growth. Notably, NarrT RC is easier than ExpT RC, a phenomenon which is poorly understood and not explained by granular text feature differences. Building upon our initial neurocognitive findings, along with existing theoretical and empirical work, we use neuroimaging coupled with behavioral methods to garner insights as to where (in the brain), when (at which text junctures), and thus how NarrT vs ExpT RC breaks down. Initial findings suggest that while both NarrT and ExpT rely on shared neurocognitive processes, they have distinctions that may be key for enhancing RC. NarrT uniquely relies on regions in a neural network linked to socio-emotional processes (e.g., dorsomedial prefrontal cortex), while ExpT uniquely relies on regions in a neural network that supports executive function/cognitive control (e.g., left dorsolateral prefrontal cortex). Our overarching hypothesis is that readers’ use of SocEMDMN vs FPN is a critical determinant of proficient situation model formation, and, thus, RC. We also posit that the enhanced socio- emotional NarrT context provokes greater connectivity between DisPDMN and SocEMDMN at key junctures in text, resulting in enriched intrinsic access to readers’ internal states, and thus a neurocognitive benefit for RC. Critically, pilot findings suggest that this enhanced socioemotional context can also be achieved in ExpT by embedding high emotion words [words with high arousal ratings] in ExpT, perhaps paving the way to bolster ExpT RC. Given that RC is a central avenue for learning new information after ~3rd grade, we are addressing a highly significant public health issue. To systematically test our hypotheses, we target 10-12 yo (N=220) who have crossed into the “reading to learn” stage to examine dynamic neural processes of ExpT vs NarrT online reading (situation model building; Aim 1); how readers’ individual differences (e.g., executive function, socio- emotional) modulate Aim ...