In July of 2015, Professor Selmer Bringsjord presented robots with a classic logic puzzle known as the "wise men riddle." It goes like this:
Three wise men are taken to the king and made to wear hats that they can't see. The king tells them that the first person to say the color of his hat wins. He also tells them that the contest is fair, and that their hats are either blue or white. The solution, deduced by the winner, is that a fair contest would only include hats of the same color, and therefore his hat is the same color as his comrades' hats.
The version of this riddle presented to the robots was different. Scientists programmed three robots to believe that two of them were no longer able to speak. They then asked the robots who could still speak. That robot spoke up to say, "I don't know," but then changed its answer once it heard its own voice.
Related: Trust of Robots is All in the Face