Most captcha solutions are based on a text rendered hard to read (or to listen to) by adding some noise to it. And most of the time, this text is randomly generated and serves only one purpose: to stop the spam. Too many humans are challenging captchas all over the world at any time to let their brain process useless data.
What can we do to solve that underutilization of brain capacity?
What can we do to solve that underutilization of brain capacity?