Neuropsychological and behavioral assessment, using repeated measurements Recent experience in incorporating neuropsychological assessment into our cohort studies from INMA (Environment and Childhood, Guxens, 2012) has resulted in fruitful exchanges of knowledge between neuropsychologists and epidemiologists. Computerized neuropsychological tests performed in repeated exams are the most sensitive tool for studying high-order brain function and development in the general population (Julvez, 2010). Moreover, these tests have been shown in population-based studies to be very sensitive to the effects of environmental and nutritional determinants (Julvez, 2013). The investigators will build on this experience to efficiently select the appropriate range of tests to cover the complex neurofunctions that rapidly develop during adolescence, such as computer tests of working memory, executive function, motor speed, visual reasoning, selective and sustained attention and inhibitory functions (Selemon, 2012). Furthermore, the neuropsychological tests will be complemented by behavioral rating scales aimed at covering the socio-emotional endpoints that are so important during early adolescence (Selemon, 2012; Morrison, 2013). The fact to evaluate other behavioral areas (i.e., social competence and ADHD symptoms) may enrich the interpretation of the findings, and, possibly it contributes to further understand the intrinsic mechanisms. One limitation is the risk of losing outcome consistency because of selecting much dispersed behavioral areas without taking into account the link between them. The best option is a careful selection of neuropsychological and behavioral tools that efficiently embrace several areas of teenage brain development. Only a few trials of n-3 PUFA among adolescents over 11 years have used computer-based neuropsychological tests (Janssen, 2014). A recent large randomized controlled trial among healthy young adults using computerized cognitive tests found that reaction time latencies and working memory were improved after 6 months of DHA supplementation (Stonehouse, 2013). A double-blind, placebo-controlled trial among children with ADHD (7-12 years) found no treatment associations, but in the observational data, a positive association between DHA levels and computerized test scores of divided attention (Milte, 2012) was reported. Large trials measuring neuropsychological functioning using repeated computerized tests within the same subjects have not yet been carried out among healthy young adolescents, and this is required to better understand `normal' brain development.