Thinking, Fast and Slow is a 2011 popular science book by Israeli-American psychologist Daniel Kahneman that distinguishes between two cognitive modes: System 1 (fast, intuitive, emotional) and System 2 (slow, deliberative, logical). The book synthesizes decades of research on cognitive biases, heuristics, and decision-making, becoming a New York Times bestseller and winning the 2012 American National Academies Communication Award, though some cited studies have faced replication concerns.