Today I spent five or ten minutes watching an elderly patron fail CAPTCHAs over and over again...
"You have to click all of them to prove you're not a robot" I say "All of them? Isn't this enough to give the gist?" "Yeah but you're not proving it to a human you're proving to a computer that you're not a computer and computers don't think about the gist they need each one individually to understand" "But wouldn't that be answering the question the way a robot would?" "The computer believes that only a human can solve this puzzle. But you have to solve it like a robot. To convince it you're human. Listen I didn't make the puzzle okay"
