Curiosity is a fundamental drive of human behavior, yet the questions ‘Why are humans curious?’ and ‘What sparks their curiosity?’ have been among the central but unresolved puzzles of neuroscience and psychology in the past decades. In this talk, I will present a series of theoretical and experimental studies exploring how intrinsically motivated reinforcement learning provides new insights into these questions — paving the way toward a unified understanding of curiosity in humans and artificial intelligence.