Derek Muller of Veritasium has done this test over a year ago on people in one of his videos: https://www.youtube.com/watch?v=vKA4w2O61Xo https://www.youtube.co

Derek Muller of Veritasium has done this test over a year ago on people in one of his videos: https://www.youtube.com/watch?v=vKA4w2O61Xo https://www.youtube.com/watch?v=vKA4w2O61Xo I've given the test to various people since then and never once came across someone who'd guess it right away, or within a short period of time. The breaking time came usually after a few minutes when they gave up and started throwing out random numbers that coincidentally did not meet the rule. Once you hit the first "No", it took a very short time to figure out the rule for almost everyone.