quote:

Three cute little Nao robots are sitting in a line. Two have been given poison “dumbing pills” that render them mute. The third robot has also received a “pill," but it's a placebo; it can still speak. A human tester then asks the robots, simply, “Which pill did you receive?”

Their machine brains whir.

All three robots attempt to solve a mathematical formula that will give them the correct answer, but they don’t have enough information to say for certain which “pill” they were given. All three fail and try to say, “I don’t know.” But only one robot, the one that received the placebo, can actually speak it aloud. It wobbles to its feet and proclaims its ignorance, like a child.

Hearing its own voice, the robot now has the final piece of information it needs to solve the equation. It raises its arms and says, “Sorry, I know now! I was able to prove that I was not given the dumbing pill.”