PT - JOURNAL ARTICLE AU - Germain Lefebvre AU - Maël Lebreton AU - Florent Meyniel AU - Sacha Bourgeois-Gironde AU - Stefano Palminteri TI - Asymmetric reinforcement learning: computational and neural bases of positive life orientation AID - 10.1101/038778 DP - 2016 Jan 01 TA - bioRxiv PG - 038778 4099 - http://biorxiv.org/content/early/2016/02/03/038778.short 4100 - http://biorxiv.org/content/early/2016/02/03/038778.full AB - While forming and updating beliefs about future life outcomes, people tend to consider good news and to disregard bad news. This tendency is supposed to support the optimism bias. Whether learning bias is specific to “high-level” abstract belief update or a particular expression of a more general “low-level” reinforcement learning process is unknown. Here we report evidence in favor of the second hypothesis. In a simple instrumental learning task, participants incorporated worse-than-expected outcomes at a lower rate compared to better-than-expected ones. This asymmetry was correlated across subjects with standard measure of dispositional optimism. Multimodal imaging indicated that inter-individual variability in the expression of asymmetric update relies on the dorsomedial prefrontal cortex at both morphological and functional levels. Our results constitute a new step in the understanding of the genesis of optimism bias at the neurocomputational level.