Most of us are familiar with the CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) test that one sometimes has to complete to prove to some website that you are a human and not a bot seeking to impersonate one. Naturally this created the usual arms race between CAPTCHA and CAPTCHA-solving technology resulting in some of tests becoming quite tricky with the lettering highly distorted and with a cluttered background, presumably to fool computers. I have often failed it and had to redo the test.
Then recently I have come across tests that said that all I had to do was check a box that was next to the text “I’m not a robot”. Although I was pleased by the simplicity and ease, I wondered how such a simple test could distinguish between humans and bots. This video explains what is going on behind the scenes. Pretty interesting!