PROJECT SUMMARY Language and reading impairments affect 16%-20% of children. Deficits in even low-level skills like word recognition persist through adulthood, and half of middle-school struggling readers show deficits in reading single words. While words are a low-level language skill at these ages, they link phonology, orthography, and meaning. Thus understanding how word recognition develops is crucial for remediating language and reading disorders. This proposal is a revision to the funded Growing Words Project, which examines the development of spoken and written word recognition during childhood. Growing Words uses eye-tracking to ask how word recognition unfolds in real-time, from the moment a word is heard (or seen) to the moment it is recognized. Our work suggests these real-time processes develop through adolescence, and children with language disorders show a distinct profile of real-time processing. Growing Words asks how real-time processing in language and reading develops from 1st to 6th grade. This study is testing 400 children longitudinally across two laboratories (including an off campus lab to enhance diversity). Children undergo measures of language, reading, cognition as well as eye-tracking measures of real-time language processing. Growing Words asks what causes a child to become more automatic (e.g., vocabulary growth, executive function, reading skills) and what are the consequences of better real-time word recognition for language and reading outcomes. This revision builds on Growing Words to examine structural properties of the brain as both a cause and consequence of differences in real-time processing, language, reading and environmental factors. Prior grants, offered a serendipitous opportunity to collect structural MRI and eye-tracking data on the same children. This led to new analyses that discovered that static properties of the brain are correlated with processing at different points in time and under different conditions. We thus leverage the infrastructure of Growing Words to investigate the neural origins of real-time processing. A subset of Growing Words participants will undergo structural MRI (measuring gray matter surface area and thickness), and diffusion weighted imaging (measuring white matter coherence) at two point, two years apart. We combine these data with a multidimensional characterization of language and reading, with eye-tracking data, and with measures of language/literacy input to address three aims. First, we ask how the development of structural brain properties leads to development of reading and language skills. Second, we identify structural properties of the brain in which development or individual differences are associated with differences in real-time lexical processing. Finally, we ask how structural properties of the brain are shaped by prior language and reading development, real-time processing skills, and language and reading input in the environment. These aims provide insig...