Reverse Turing test if the subject is or is not human. As of 2004, such procedures, called CAPTCHAs, are used in some anti-spam systems to prevent automated bulk use of communications systems. The use of captchas is controversial. Circumvention methods exist that reduce their effectiveness. Also, many implementations of captchas (particularly ones desired to counter circumvention) are inaccessible to humans with disabilities, and/or are difficult for humans to pass. Note that "CAPTCHA" is an acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart" so that the original designers of the test regard the test as a Turing test to
Turing test plausible by contemporary researchers in artificial intelligence. In a 2008 paper submitted to 19th Midwest Artificial Intelligence and Cognitive Science Conference, Dr. Shane T. Mueller predicted a modified Turing test called a "Cognitive Decathlon" could be accomplished within five years. By extrapolating an exponential growth of technology over several decades, futurist Ray Kurzweil predicted that Turing test-capable computers would be manufactured in the near future. In 1990, he set the year around 2020. By 2005, he had revised his estimate to 2029. The Long Bet Project Bet Nr. 1 is a wager of $20,000 between Mitch Kapor (pessimist) and Ray