ReCAPTCHA: Fight Spam And Digitize Books

Thanks to the wonderful world of spammers most websites these days rely on CAPTCHA images to force users to prove they are human before accepting comments or other user feedback. In fact humans solve roughly 60 million CAPTCHAs a day according to a the people behind reCAPTCHA a group that wants to leverage that effort […]

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Thanks to the wonderful world of spammers most websites these days rely on CAPTCHA images to force users to prove they are human before accepting comments or other user feedback. In fact humans solve roughly 60 million CAPTCHAs a day according to a the people behind reCAPTCHA a group that wants to leverage that effort to help digitizing books.

ReCAPTCHA wants to improve the process of digitizing books by sending words that cannot be read by computers to the web in the form of CAPTCHAs for humans to decipher.

The idea behind reCAPTCHA is that, as long as we're all solving these CAPTCHA puzzles, why not throw in some minimal additional data? By adding a second image with an unsolved word from the Internet Archive book scanning project, ReCAPTCHA allows users to channel their CAPTCHA solving skills into real world benefits.

The Internet Archive and other similar initiatives are busy scanning the world's books and converting them to text via OCR technology. But of course OCR is far from perfect, often there are unreadable words in the scans that require a human to make a decision. Tedious work to be sure.

The reCAPTCHA idea works by taking each word that cannot be read correctly by OCR and creating a CAPTCHA image out of it.

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But, you may be thinking, if the OCR software doesn't know the word, then how does the CAPTCHA software know that the solution has been correctly entered?

Here's an explanation from the reCAPTCHA site:

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.

Since we're all stuck solving CAPTCHAs anyway, the reCAPTCHA project makes perfect sense. If you'd like to use the system head over to the reCAPTCHA site and have a look at the various options for including the CAPTCHAs on your site — there are already plugins for WordPress and PHP.

[via Hackszine]

ReCAPTCHA in action:

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