CAPTCHA, for those of you just joining us, stands for Completely Automated Public Turing test to tell Computers and Humans Apart. Essentially, it’s a challenge-response test used to distinguish between humans and spam-spewing robots. What’s interesting about reCAPTCHA’s implementation is that it’s used for digitizing books.

“Since computers have trouble reading squiggly words like these, CAPTCHAs are designed to allow humans in but prevent malicious programs from scalping tickets or obtain millions of email accounts for spamming,” Google explains in a post to the company blog. “But there’s a twist–the words in many of the CAPTCHAs provided by reCAPTCHA come from scanned archival newspapers and old books. Computers find it hard to recognize these words because the ink and paper have degraded over time, but by typing them in as a CAPTCHA, crowds teach computers to read the scanned text.”

An ingenious idea, crowdsourcing book transcriptions in this way. An effective one too: reCAPTCHA boasts 99.5 percent accuracy at the word level.

Little wonder, then, that Google (GOOG) has acquired it. The company can clearly put reCaptcha’s technology to good use, not just as a security measure, but as a means of improving its own massive book-scanning project.

CAPTCHA, for those of you just joining us, stands for Completely Automated Public Turing test to tell Computers and Humans Apart. Essentially, it’s a challenge-response test used to distinguish between humans and spam-spewing robots. What’s interesting about reCAPTCHA’s implementation is that it’s used for digitizing books.

“Since computers have trouble reading squiggly words like these, CAPTCHAs are designed to allow humans in but prevent malicious programs from scalping tickets or obtain millions of email accounts for spamming,” Google explains in a post to the company blog. “But there’s a twist–the words in many of the CAPTCHAs provided by reCAPTCHA come from scanned archival newspapers and old books. Computers find it hard to recognize these words because the ink and paper have degraded over time, but by typing them in as a CAPTCHA, crowds teach computers to read the scanned text.”

An ingenious idea, crowdsourcing book transcriptions in this way. An effective one too: reCAPTCHA boasts 99.5 percent accuracy at the word level.

Little wonder, then, that Google (GOOG) has acquired it. The company can clearly put reCaptcha’s technology to good use, not just as a security measure, but as a means of improving its own massive book-scanning project.

That’s the argument that Brewster Kahle, co-founder of the Internet Archive, made in an op-ed in the Washington Post, in which he writes that the settlement “provides a new and unsettling form of media consolidation.”

Google’s book-scanning project drew outcry and a class-action lawsuit from the Authors Guild and the American Association of Publishers, who said the Internet company was violating copyright laws by scanning copyrighted works. A settlement agreement was reached in October of 2008 which would allow publishers and authors to share Google’s profits from the sale of digital versions of copyrighted works. The deadline for plaintiffs to object to or opt out of the settlement was recently extended to Sept. 4, 2009.

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