What is the Phrase for split personality in R L Stevenson's movie?

The phrase for split personality in Robert Louis Stevenson's story, particularly as adapted in film versions like "Dr. Jekyll and Mr. Hyde," is often referred to as "dual identity" or "doppelgänger." The narrative explores the conflict between the respectable Dr. Jekyll and his darker alter ego, Mr. Hyde, symbolizing the struggle between the good and evil aspects of human nature. This theme highlights the complexity of identity and morality.