ReCaptcha: Stop Spam, Digitize Books

Some readers may have noticed that I’ve changed my method of listing my e-mail address on my web pages. I now use ReCaptcha.

ReCaptcha hides a portion of the e-mail, and to access the entire e-mail, you must type in two words. This helps stop spammers, obviously.

But — and this is the really clever part — it also helps to digitize books. So we’re getting some extra value for our time spent blocking spam.

ReCaptcha is a service of Carnegie Mellon University. Here’s the relevant description:

About 200 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.

To archive human knowledge and to make information more accessible to the world, multiple projects are currently digitizing physical books that were written before the computer age. The book pages are being photographically scanned, and then transformed into text using “Optical Character Recognition” (OCR). The transformation into text is useful because scanning a book produces images, which are difficult to store on small devices, expensive to download, and cannot be searched. The problem is that OCR is not perfect.

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.

This is very clever. Two problems, one elegant solution. Nicely done.