PROJECT SUMMARY Language and reading impairments affect 16%-20% of US children, and are stable, persisting through adolescence and adulthood. Deficits in even low level skills like phonological processing and spoken word recognition persist through adulthood, and half of middle-school struggling readers show deficits in decoding and written word recognition. This proposal examines the development of spoken and written word recognition during late childhood. While words are a low-level language skill at these ages, they are central to language, linking phonology, orthography, and meaning. At a cognitive level, word recognition is seen as a competition process. As the input (e.g., wizard) is heard (or read) people consider multiple partially matching words (whistle, lizard) which compete over time. Prior work assessed this in children using a paradigm in which listeners match words to pictures while eye-movements are monitored. As listeners begin to hear a word their eyes move between candidates. These fixations reveal momentary consideration of alternative words and trace the dynamics of competition over milliseconds. We applied this to children, showing that competition is resolved more automatically between 9 and 16 years. Adolescents with language impairment showed a different pattern: they were similarly automatic, but did not fully resolve competition by the end of processing. This research documents that real-time processing develops, but it is unclear how. In older children, it is likely due to multiple causes such as vocabulary growth, the organization of phonological systems, the onset of reading instruction, and changes in executive function. This project examines the development and disorders in the automaticity and degree of competition resolution during lexical processing. It examines both spoken and written word processing to unpack the relationship between language and reading, and identify outcomes (good and poor) linked to differences in real-time processing. The first aim is to determine the cognitive and developmental factors that shape real-time word recognition, and the consequences of this for language and reading outcomes. We conduct an accelerated longitudinal study of 400 children (normal and impaired) between 7 and 12 combining eye-tracking measures of word recognition with tests of phonological processing, reading, vocabulary, and executive function. The second aim uses cross-sectional laboratory studies to examine the consequences of differences in real-time processing for learning and for related processes like semantic processing (meaning) or orthographic decoding (mapping sound to print). The third aim uses laboratory training procedures to understand plasticity in real-time lexical processing; this may pave the way for potential interventions targeting lexical processing. Finally, the fourth aim develops computational models of normal and disordered lexical processing to attain a deeper understanding of what mechan...