The study to explore the development of these abilities with age, and called "Development of the conflict detection during the reasoning - Decor" will take place at CYCERON center and will include two groups of 22 participants: adolescents and young adults (N = 44). More specifically, this study aims to compare the changes in the brain of adolescents and young adults when conducting reasoning tasks for which there may be a cognitive conflict. Both groups of participants then spend an MRI (Magnetic Resonance Imaging) focused on the brain and in which they will carry out two classic tasks covering the main areas of reasoning (probabilistic and economic). Each of these tasks will be manipulated to include, or not, of making information call intuition to create or not a conflict between the correct answer (logic, normative) and biased response (intuitive, heuristic). Because of the major implication of this brain region in cognitive inhibition processes [of intuitive answer], measured brain activity in the anterior cingulate cortex (ACC) during both tasks version "with" or "no" conflict will be compared between groups. To better understand the links between the development of the CCA from adolescence to adulthood and conflict detection, activity measurements will be correlated with a part in morphometric measurements taken from the same area (volume Substance Grise - SG; characteristics of cortical sulci) and secondly to cognitive measures (executive functions - inhibitory control). This cross-sectional study focused on two age groups: 11-15 years and 19-25 years. For each age group, the participation of men / boys and women / girls will be balanced up.