We have all been to sites where we have to type in a word or phrase that demonstrates that we are not a spider or spam bot but a human attempting to access a page or purchase an item. When you look at the word or phrase it looks like a warped rendering with distorted letters. The program that provides the fuzzy looking words is called CAPTCHA. According to recaptcha.net, “The term CAPTCHA (for Completely Automated Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University. At the time, they developed the first CAPTCHA to be used by Yahoo.”
I always understood the funky phrase or word was to stop Optical Character Recognition systems from deciphering them, submitting the words back, and falsely validating itself to as a human being. While it does that, recaptcha.net wants to use that few seconds of human effort of typing in the words into a textbox for noble purposes.
About 60 million CAPTCHAs are solved by humans around the world every day. In each case, roughly ten seconds of human time are being spent. Individually, that's not a lot of time, but in aggregate these little puzzles consume more than 150,000 hours of work each day. What if we could make positive use of this human effort? reCAPTCHA does exactly that by channeling the effort spent solving CAPTCHAs online into "reading" books.
reCAPTCHA improves 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. More specifically, each word that cannot be read correctly by OCR is placed on an image and used as a CAPTCHA. This is possible because most OCR programs alert you when a word cannot be read correctly.
To help with this go to http://recaptcha.net/learnmore.html. Moreover there is an API at http://recaptcha.net/apidocs/captcha/.
Hey, in about 30 seconds I helped digitized five words!
