Researchers told three robots that two of them had been given a "dumbing pill" that stops them from talking. In reality, a button pushed by the researchers prevented them from speaking.
None of the robots knew which one was still able to speak, and when asked which one had the ability to speak, the three robots all attempted to say "I don't know."
When only one of the robots actually spoke, it recognized its voice and understood that it was not silenced.
"Sorry, I know now," the robot said. "I was able to prove that I was not given a dumbing pill."
However, as the robots presumably are coded the same, it could be said that all three have the capacity to pass the test.
While the task is a simple one for humans, it is a bit more complex for a robot. The robot must first listen to and understand the question asked, hear and identify its own voice, and then connect that back to the original question.