Despite the severe clinical impact of socioemotional difficulties in patients with major depressive disorder (MDD), objective behavioral markers of social impairment are lacking. One of the two core symptoms of depression, anhedonia, the lack of motivation and/or pleasure in rewarding activities, has been suggested as a major determinant of altered social behavior, including decision-making in socioemotional contexts. On the other hand, there is suggestive evidence that anhedonia is also associated with measurable changes in postural and gait parameters in depression. The WANDERS project aims at examining the relationship between anhedonia, posture and gait, and socioemotional decision making. Based on our theoretical model, we hypothesize that anhedonia in the general population and in individuals with MDD causes changes in both posture/gait parameters and socio-emotional decision-making due to common neural determinants in fronto-striatal dopaminergic circuits. In the first work package (WP1), we will induce reduced positive affect (anhedonia) in healthy participants via sleep deprivation to experimentally test our hypothesis. Participants will perform a social decision-making task, consisting in approaching or avoiding emotional individuals in virtual reality (VR) while three-dimensional (3D) motion parameters are recorded. WP1 will elucidate the relationship between anhedonia, postural and gait changes, and socioemotional decisions in the general population by combining VR, 3D motion analysis, and computational models. WP2 will translate these findings into the clinic to generalize the results of WP1 to a sample of MDD patients. The WANDERS project fits within the scope of the CES 28 by investigating a central dimension of human sociality in both healthy and clinical populations. This will help establishing a novel framework for understanding the affective determinants of social decisions and unravel objective behavioral markers of the quality of social life. The solid background of the scientific coordinator, together with the decisive help of a high-quality interdisciplinary network of collaborators, will allow realizing the project.