Think Again

Chimpanzees can weigh evidence and update their beliefs like humans do

- -Cody Cottier

YOU GENERALLY HAVE REASONS, good or bad, for your beliefs. You can reflect on those reasons: “Why do I think there’s a serial killer in the attic? It’s because the floor creaked.” And, paragon of rationality that you are, you can also adjust your beliefs when additional evidence demands it: “Having scoured the attic, baseball bat in hand, I must conclude that it’s just an old, creaky house.”

This cognitive skill is known as belief revision. It’s long been considered a hallmark of human rationality that distinguishes us from other animals. It relies on a reflective awareness of our own thought processes—thinking about thinking, or metacognition—that other species don’t obviously possess. But a recent study in Science shows that one of our closest evolutionary relatives also reasons in surprisingly sophisticated ways.