Capgras syndrome is a psychological condition where a person believes that someone close to them, such as a family member or friend, has been replaced by an identical impostor. This delusion can occur in various mental health disorders, including schizophrenia and dementia. The syndrome is named after the French psychiatrist Joseph Capgras, who first described it in 1923. It is thought to arise from a disconnect between the brain's recognition of faces and the emotional response associated with those faces, leading to confusion and distress for the affected individual.