Oxytocin modulates several aspects of social cognition in both animal models and man. There is evidence that dysregulation in the oxytocin system, including oxytocin receptors (OTR), may contribute to the social deficits in psychiatric disorders such as autism spectrum disorder, depression, and schizophrenia. In this study, researchers will synthesize and characterize candidate selective, radiolabeled small molecules that bind to the OTR with the ultimate goal of generating tools for investigating the relationship between OTR distribution in the brain and human social cognition and psychopathology. These labeled molecules will be used in positron emission tomography (PET), an imaging technique that produces a three-dimensional image or picture of functional processes in the brain. The development of a PET ligand to detect and quantify oxytocin receptor in the living brain may therefore prove to be a useful tool for examining the relationship between oxytocin receptor distribution and social cognition in psychiatric patients and may lead to a better understanding of the etiology of social deficits in these disorders.