[myNetWords.com] : Captcha

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Captcha

Updated : Thursday 19 April 2012


Example of a captcha

A captcha isn’t a mispronunciation of Chapka, the name for those Russian fur hats. In fact it’s not Russian at all, but an acronym, and a rather tedious one at that: Completely Automated Public Turing test to tell Computers and Humans Apart. All you really need to know is that a captcha is a test designed to make sure that the person posting a message in a forum or a comment on a blog really is an actual flesh-and-blood human and not some malevolent robot. (There’s an example shown below.) In practical terms, the captcha test usually consists of asking you to reproduce a series of letters that pop up in a window. If you use forums or post comments on blogs, or belong to social networking groups or hubs, the chances are you will have done these tests, and now you know the name for them. The technique is used by website editors and bloggers to reduce the risk of spam and avoid having their websites infected by advertising or messages of a political or activist nature.

The captcha is a type of Turing test, designed to detect artificial intelligence. Standard Turing tests are set by a human to be performed by a machine, but a captcha is really a reverse Turing test, meaning that this one is set by a machine to be performed by you, the human. So there you have it.

To be sure that it is you who is answering and not a computer, the Captcha test asks you to do something that would present a challenge to an artificial intelligence: for instance, the letters that appear can look bent and distorted and the background colour changes. Or the letters might be struck through, to make the word less legible, or even overlap, with the tail of the P biting into the top of the next letter, an S, and so on. Tests like these are great for the ego, you are almost bound to get them right. And it’s good to know you’re more intelligent than some automaton: the science fiction movies might make you wonder, but with the captcha, honour is saved. Except if you have bad eyesight or your glasses need adjusting: the fact remains that some of these tests can defeat not just computers but humans as well. That said, if you fail the test, fear not, you’ll get it right next time: you’ll be given another, easier captcha test. And for those who are truly allergic to these things, the days of this test are numbered, as increasing numbers of forums, blogs and websites now let you post comments freely, without having to go through the captcha process, provided you have identified yourself from a social networking site – that’s called a social login.