This study is attempting to understand whether 30-minutes of a new ear stimulation technology can reduce pain in healthy individuals. Participants in this trial will attend two experimental visits, during which they will receive ear stimulation during the intravenous administration (I.V.) of either saline or naloxone. During each visit, the amount of thermal pain participants can tolerate will be determined before and after ear stimulation. Brain scans will also be collected before and after ear stimulation. Each visit should last about 3 hours.