"A fundamental research question of several disciplines concerns the description, explanation and prediction of human behavior in social contexts. While significant research had been devoted to higher order social capabilities, much less is known about basic principles that are underlying these functions. This is especially true for social attention which is at the heart of every higher order social function but has neither been systematically examined in naturalistic environments before nor has it been linked to the extensive body of psychological and neuroscientific research on basic principles of attention. As a consequence, it is unknown whether the neural computation and the behavioral expression of social attention is similar or divergent to other forms of non-social attention.The current project will fill this gap by comprehensively characterizing the distinctive features of social attention on the behavioral and neural level using a multimodal approach involving eye tracking measures, neuropeptidergic manipulations, fMRI and EEG. I propose that social elements in complex environments are automatically selected and preferentially processed which is mediated by a specialized subcortico-cortical system that allows for tagging social cues in the visual field. These hypotheses will be tested in healthy volunteers and in clinical disorders with well-described impairments in social functioning. Finally, immersive virtual reality environments will be used that allow for examining active behavior and attentional allocation in complex social situations which approximate naturalistic field settings.By highlighting ecological validity, this project will provide unique insights into the mechanisms of social attention in healthy individuals and it will identify maladaptive attentional processes in individuals with impaired social functioning. Building on these data, the proposed research will provide a new framework for understanding human behavior in social situations."