The goal of this observational study is to characterize the brain processes of pain avoidance learning dysfunctions in individuals with opioid use disorder (OUD). The main questions it aims to answer are: Compared with healthy controls, do those with OUD exhibit impaired avoidance learning in response to pain? What are the brain processes that are associated with this avoidance learning dysfunction? Do these brain processes serve to predict future use or relapse? Researchers will compare those with OUD and healthy controls to determine avoidance learning dysfunction and its relationship with opioid use. Participants will be performing a learning task inside an fMRI scanner. Those with OUD will also be followed up for a year to determine future opioid use.