PROJECT SUMMARY/ABSTRACT Because this project addresses the mechanisms that contribute to Developmental Language Disorder (DLD), a highly prevalent communication disorder in the United States, it is directly relevant to the mission of NIDCD. Ultimately, the outcomes may offer solutions to three significant problems: how to identify DLD regardless of language(s) spoken, how to identify DLD in adults, and how to distinguish DLD from other related conditions. Our overarching hypothesis is that a deficit in short-term verbal memory (stVM) is endophenotypic of DLD. Our current objectives are to 1) delineate the role of linguistic long-term memory, attention, and their interface in the stVM deficit and 2) demonstrate the cascading effects of the stVM deficit on the integrity of the language system. Aim 1: To determine the contribution of structure and meaning in linguistic long-term memory to the stVM deficit. We will manipulate prosodic structure and word meaning during nonword repetition (NWR) (1a) and grammatical structure during real phrase repetition (1b) and use linear mixed-effects models to test the hypothesis that individuals with DLD can use linguistic long-term memory to support stVM, but they benefit more from meaning than structure. 1b also offers a chance to explore the nature of stVM per se, specifically, to observe the children’s rehearsal strategies. Aim 2: To determine the contribution of attention to the stVM deficit. We will manipulate the burden on attention during encoding by pairing a visual search task with the NWR of sequences with high or low phonotactic probability and use linear mixed-effects models to test the hypothesis that the stVM deficit reflects difficulties in attentional control during encoding. This experiment also offers an additional test of the contribution of linguistic long-term memory to stVM function. Aim 3: To determine the relationship between sustained attention, stVM, and linguistic long-term memory. We will conduct two tests of each construct and use principal component analysis and multiple regression to test the hypothesis that language moderates the relationship between sustained attention and stVM. Aim 4: To simulate the cascading effect of the stVM deficits. To test the stVM deficit as an endophenotype, we will provide higher and lower support for novel word form encoding in children with typical language development and observe the subsequent influence on two aspects of the system, semantic category knowledge and sentence comprehension. We will use linear mixed-effects models to test the hypothesis that the stVM deficit has downstream consequences for the integrity of the overall language system.