You’ve seen those little authentication tests on web-based forms, probably more this year than last. They’re called CAPTCHAs which is an acronym for Completely Automated Public Turing test to tell Computers and Humans Apart. Just a quick bit of history—in 1950 Alan Turing (considered the father of modern computer science and credited with breaking the Enigma ciphers during WWII), created a test to determine whether a computer demonstrated thought. The test was simple…with a computer hidden in one room and a human hidden in the other, converse with each. If you can’t tell which is the human, then the computer is demonstrating thought.
The CAPTCHA is really a reverse Turing test (we want to prove that you’re a human) but you get the idea.
Today, I added a CAPTCHA to the comments for this blog but it’s a very special, library-oriented one. This CAPTCHA (actually called reCAPTCHA) is helping digitize books for the Internet Archive.
How? It shows two words: one it knows and one that it had difficulty resolving during the OCR process. You’re asked to type in both words as you read the image. Assuming your input matches the known meaning of the first word, the CAPTCHA assumes you’ve correctly interpreted the second term as well and uses that input to correct the OCR work. You’re authenticated (you must be a human, not a spam-bot) and you’ve done a small bit of work to help bring knowledge to the masses! I’d like to see more library-related sites use this system and will add it to our library’s “comment/suggestion” form soon.