He gets it slightly wrong on how it works. One is not verified by a computer and one verified by a user. Here's a quote from http://www.google.com/recaptcha/le

He gets it slightly wrong on how it works. One is not verified by a computer and one verified by a user. Here's a quote from http://www.google.com/recaptcha/learnmore http://www.google.com/recaptcha/learnmore """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."""