Are humans the only animal that knows what they don’t know? A study by researchers at Yale and Harvard shows that rhesus monkeys also spontaneously recognize when they are ignorant and need to seek out more information.

The findings are published in Psychological Science, a journal of the Association for Psychological Science.

“Metacognition— the ability to think about our own thoughts— has long been considered a hallmark of being human,” said Laurie Santos, Yale psychological scientist and senior author of the study. “We all know the difference between feeling like we know something for sure and feeling like we’re not all that certain. We know when we need to Google something.”

But do other animals recognize their own uncertainty?  Previous studies have shown that animals can recognize when they are uncertain, but these animals were typically exposed to the experimental problem over an extended period of time.