1. Determine the effectiveness of long-term intervention (30g of walnut kernels per day for 6 months) in enhancing neuropsychological development. This project will provide a new understanding of the role of walnut intake (as a surrogate of n-3 PUFA intake) in the brain development of teenagers. This has an important impact for global health interventions due to the affordability of such interventions in diverse societal groups. A major goal in public health research is to develop effective, cost-effective and feasible health recommendations.