Have you seen the websites on which you have type out the misshapen letters in a little box before you leave a comment? In that moment, you are doing the work of translation.

In fact, your brain has deciphered words that had baffled the scanning software used for an enormous project to digitize every public domain book in the world.

“We can coordinate literally millions of people on the Internet to work together to do something that computers cannot do,” says Luis von Ahn, an assistant professor of computer science at Carnegie Mellon University in Pittsburgh.

… Some 200 million of these words, dubbed “Captchas” for Completely Automated Public Turing test to tell Computers and Humans Apart, are typed every day by people around the world.