> But if a computer can't read such a CAPTCHA, how does the > system know the correct answer to the puzzle? Here's how: > Each new word that cannot be rea

> But if a computer can't read such a CAPTCHA, how does the > system know the correct answer to the puzzle? Here's how: > Each new word that cannot be read correctly by OCR is > given to a user in conjunction with another word for which > the answer is already known. The user is then asked to > read both words. If they solve the one for which the > answer is known, the system assumes their answer is > correct for the new one. The system then gives the new > image to a number of other people to determine, with > higher confidence, whether the original answer was > correct. http://recaptcha.net/learnmore.html http://recaptcha.net/learnmore.html