[citation][nom]everlast66[/nom]This explains why sometimes you can go through the captchas with random text. If they rely on the users to enter data, then it is no longer a check buy just an entry box, they don't have anything to compare against, ant it always passes. So if you see your street name on GMaps as "fghsdfs" don't be surprised.[/citation]
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.