PROJECT IV ![NatPAT logo][1] **Sara Hart** Jeanette Taylor Colleen Ganley Elliot Tucker-Drob, Consultant Using an ingenious system for identifying twins from an existing state-wide database that contained longitudinal data of reading and reading-related variables, a diverse sample of thousands of twins was collected in a previous funding period. The large-scale twin sample enabled the detection of effects that would not have been possible with typical twin studies. An example is the finding that teacher quality moderates genetic effects on early reading, a finding that also was published in Science (Taylor et al., 2010). The potential impact to the field of this project is replicating the method on a much larger sample that includes both reading and math data, thereby enabling the study of genetic and environmental etiology of co-occurring problems in both domains at a more fine grain level than has been possible for most studies. Specifically, reading and math problems represent an important public health issue for children in that they are associated with various negative outcomes including school failure, limited occupational success, and juvenile delinquency (Geary et al., 2001; Reynolds et al., 2001). Of US fourth-grade students, one-fourth fail to reach even partial mastery of grade-level knowledge in reading, and one-fifth fail to reach partial mastery of grade- level knowledge in math (NCES, 2015), highlighting the prevalence of reading and math difficulties in childhood. Given we know that children who struggle in reading often also struggle in math, it is important to identify influences on the development of both reading and math. The overall goal of the proposed research is to uncover salient factors, including genetic and environmental influences, which contribute to the co- development of reading and math performance, at a critical developmental point (elementary school). We will identify the first nationally-representative US twin sample through the proposed National Project on Achievement in Twins (NatPAT). The NatPAT sample will comprise 7,668 pairs of twins located across the US, and will be uniquely situated to address the overall goals. [1]: http://www.idcdlab.com/uploads/9/1/0/5/9105950/published/natpatlogo_1.png?1510059410