Background

CAPTCHA = "Completely Automated Public Turing test to tell Computers and Humans Apart"

• version 1 invented in 1997 by two groups working in parallel
• Luis von Ahn contributed early work in 2000 (at the age of 22), completed his PhD in 2005 the first work on Games With A Purpose (GWAP) a famous example of which the ESP game pits two people against each other to create metadata for an image
  • ESP was licensed by Google and turned into Google Image Labeler, launched in 2006-2011, and relaunched in 2016 as Crowdsource by Google
    • pretty impressed with the gamification, similar to Google Maps Guides
  • in 2007 comes up with reCAPTCHA, in the first year after launching “humans correctly deciphered and transcribed more than 440 million words, roughly the equivalent of 17,600 books.” source, later acquired by Google in 2009
  • MacArthur Fellowship in 2006 and starts Duolingo in 2009
• Because the test is administered by a computer, in contrast to the standard Turing test that is administered by a human, a CAPTCHA is sometimes described as a reverse Turing Test

Timeline

• 2008, text CAPTCHA basically solved with following success rates of 95-100%
  • Results
• 2013, Google’s reCAPTCHA implements behavioral analysis, e.g. simple checkbox with additional steps if the user is deemed a risk

Crowdsource by Google, some categories are “solved”?

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