Judith Keppel was a single question away from taking home £1 million. She was in the final round of a British quiz show, and she had to face one last challenge to become the show's first victor: “Which king was married to Eleanor of Aquitaine?”After a brief discussion with the show's host, Chris Tarrant, she settled on Henry II. Then Tarrant asked her the killer question, the moment when contestants often agonize the most: “Final answer?” Without missing a beat, Keppel confirmed. The audience broke into cheers as it was revealed she had won. Keppel did not waver on that November day in 2000 because of her metacognition. The term, coined by psychologist John Flavell in the 1970s, refers to our ability to evaluate our own thinking. Is the answer to a password prompt correct? Is a particular memory from childhood accurate? Will we find it easy or difficult to learn a new language? Metacognition is an internal tribunal that rules on the soundness of our mental representations, such as a memory or judgment. Keppel's metacognition gave her answer a resounding endorsement.