The proposed project is designed to uncover the neural correlates of processing two languages as bilinguals transition from novice to intermediate L2 speakers in early childhood. To achieve this, the proposed project will use Near Infrared Spectroscopy (NIRS), which measures neural activity indirectly via changes in deoxyhemoglobin and hemoglobin which is correlated with blood flow and energy metabolism. This methodology is child friendly allow us to extend testing to children that are preschool age. Recent research has found that adults who learned a second language early in life exhibit remarkable plasticity in their language processing abilities. These children transition from L1 to L2 dominance during the first five years of schooling and maintain a pattern of L2 dominance into adulthood. To elucidate the nature of the neural correlates of bilingualism in child L2 learners, the proposed project will test bilingual children between the ages of 3-8, which correspond to time points corresponding to very early stages of L2 acquisition up to more advanced L2 knowledge. Children will be asked to listen to auditorily presented words while being scanned with NIRS. The results from the proposed studies will help to elucidate the neural substrates that differentiate first from second language acquisition during childhood. Finally, the proposed studies will compare predictions from two competing models which view L2 acquisition as involving differential use of cognitive control or as involving changes in sensorimotor processing. PUBLIC HEALTH RELEVANCE: The proposed project is designed to extend the scope of the parent grant by examining the neural correlates of processing two languages as bilinguals transition from novice to intermediate L2 speakers as they transition from preschool years to early grade school. The results from these studies should help to provide background which will help clinicians in the assessment and treatment of young L2 learners with language disorders.