PROJECT SUMMARY CORE A: ADMINISTRATIVE CORE All research projects and Cores will benefit from the services provided by the Administrative Core. The Administrative Core will be responsible for the overall operation and coordination of the CLDRC, including both scientific and administrative activities. The Administrative Core will be responsible for ascertainment of all new participants for the Research Projects, including 250 new twin pairs in which at least one twin exhibits significant learning or attentional difficulties, and 100 twin pairs in which neither twin exhibits any difficulty with learning or attention. In parallel, Core staff will recruit a separate sample of 100 bilingual Hispanic adolescents who participated in an earlier study of reading difficulties by CLDRC investigators, providing a unique opportunity to assess the manifestation and developmental outcome of RD in this understudied population. The Administrative Core will also supervise the implementation of data sharing and publication plans; monitor and mitigate known and emergent risks to the Center objectives, and evaluate the explicit benchmarks that will be used to measure the success of the Center. Finally, the Administrative Core will invite and coordinate the involvement of the External Scientific Advisory Board.