What is the Need to Create a Turing Test?
Who Uses CAPTCHA?
Designing a CAPTCHA System:
Most, however not all, CAPTCHAs depend on a visual test. A few Websites execute an entirely unexpected CAPTCHA framework to distinguish people and PCs one from the other. For instance, a client is given 4 pictures in which 3 contains pictures of creatures and one contains a blossom. The client is made a request to choose just those pictures which contain creatures in them. This Turing test can undoubtedly be tackled by any human, however practically inconceivable for a PC.