The problem of bilingual education has become especially acute in light of globalization, where an increasing number of countries are faced with multilingual societies. In the United States, the educational challenges associated with integrating non-native populations into society are particularly challenging for the significant cohort of language-minority individuals who come to the task of acquiring a new language after the acquisition of literacy in L1 has matured. The proposed project comprises a comprehensive investigation of the neurocognitive parameters that affect how adolescents acquire and learn to read a new language. The project will employ a longitudinal design in which we will recruit cohorts of adolescents ranging from a basic to medium literacy level in a second language (L2) and track skill development with both behavioral and fMRI measures over 24 months. Cohorts will be recruited in both Israel and the U.S.; thus, each language will serve as both L2 and L1. Specific aims are: 1) To investigate how learning to read in L2 is jointly determined by the linguistic structure of L1 and by individual differences in neurocognitive capacities of the reader; 2) To investigate whether acquiring reading fluency in a second language necessarily depends on acquiring native- like neurocognitive markers; and 3) To investigate the linguistic and general neurocognitive consequences of learning a new set of statistical regularities in L2. In addition, a cross-sectional fourth aim contrasts Hebrew vs. Spanish as L1 in order to assess both the generality of findings from Hebrew and investigate the impact of qualitative differences in the underlying linguistic structures of an L1 on neurocognitive indices of reading English. This proposed research will directly inform theories of second language learning, and holds promise to inform research on optimal approaches to second language curriculum development. Moreover, the focus on individual differences in L2 learning, at the level of brain and behavior, will yield new insights into challenges to second language literacy acquisition, given the characteristics of an individual's native language and linguistic environment.