Harnessing crowds seems like a popular theme these days. Amazon’s mechanical turk is an example of such a service.
Google bought recaptcha a company that provides free anti-bot captcha tests for websites. But there is more to this purchase than meets the eye. Google sees this acquisition as a way to have crowds help with digitization of books for its google books project. Google sees recaptcha as a crowd computer (its own version of mechanical turk for help identifying digital images).
For all the websites out there using reCaptcha – Google says there are above 100,000 – this now means you’ll also help Google’s efforts now. (You continue to get something in return, of course: a form of free spam protection for your site.) The reCaptcha technology might have been feasible to duplicate for Google, but the installed existing user base for reCaptcha is possibly the actual gold Google was after. ReCaptcha mentions they’re serving 30 million Captchas daily and that generally, people spend roughly 10 seconds on a captcha – that’s quite some human computing power Google snapped up there.
Technically, here’s how reCaptcha works. Captchas (short for Completely Automated Public Turing test to tell Computers and Humans Apart) are deliberately distorted to make them hard to read, so that they can’t be easily solved with existing OCR algorithms. At reCaptcha – which webmasters can easily plug-in to their existing forms and configure via e.g. a JavaScript API – you’ll always be presented with two, not just one words. The trick is that reCaptcha already knows one of the words, but wants you to help solve the other word (if enough other people solve that other word similarly, the system gains confidence that it now knows what that word reads). So you can say one word is the actual Captcha test word… while the other word deliberately spends more of your time than needed for the robot test by letting you turn books into text. It’s these extra seconds that you spend solving the secondary, unknown word that make up the CPU of that crowd computer Google now owns.
Right now, Google can use this crowd computer to improve searching and highlighting text for projects like Google Books. Improving by correcting old words, increasing their confidence threshold, or cracking new unknown words – and perhaps letting their software learn from its mistakes, or by running automated tests against reCaptcha when they try out new versions of their OCR. But who’s to say that in the future, we’ll not be solving other captcha tasks? Telling humans and bots apart is not necessarily restricted to text-reading tests. There are other puzzles out there which are tough for today’s AIs, but easy for humans, which might benefit a Google project.
For instance, a captcha may show you a thumbnail collection of a dozen images and ask you to click on all images showing a cat. (I’m not sure how feasible this particular example would be for Google, but it’s just to illustrate the general different directions captchas can take.) For most images Google knows whether it’s a cat or not, but for one image, Google only suspects that it’s a cat based on keywords found on the same page the pic was hosted on. If many people click that picture, Google may gain confidence that it’s indeed a cat (or conversely that it isn’t), and rank it accordingly in Google Images.
Hmm. This is quite neat.