Additional Study Information: The goal of the project is to identify differences in learning in obsessive-compulsive disorder (OCD) by measuring the activity of the brain while participants complete computer tasks. Eligible participants will be asked questions about their medical and psychiatric history and perform tasks on a computer while an electroencephalogram (EEG) is recorded. While most study procedures will be conducted online or via videoconferencing, this study requires two in-person visits occurring eight weeks apart. During those eight weeks, participants with OCD will receive exposure and response prevention (a specific type of psychotherapy for OCD). Participants will be compensated for their time and effort.