CAPTCHA introduction (cont. 1)

從字義上來看，Captcha是一種“涂林測驗”（Turing test），這是由計算機科學之父涂林（Alan Turing）於1950年所提出，用來作為判斷人工智能高低的依據。這個方法是由一個人扮演裁判，在不直接與受測者面對面接觸的情況下，分辨出受測者究竟是電腦或是人類。若受測者是一台電腦，但裁判認為它是個人類的話，則這台受測的電腦就通過了涂林測驗。但Captcha不同於傳統的涂林測驗(由人作為裁判)，而改由電腦做裁判來分辨受測者是電腦或是人類，因此也有人稱之為“逆向涂林測驗”（reverse Turing test）[3]。

At literal meaning, CAPTCHA is a kind of “Turing test” which is proposed by Alan Turing to determine the quality of an artificial intelligence. This test needs a person to be a judge who can not contact to the other parties. And the parties include one human and one computer. If the judge can not identify which one is the computer, the computer will pass this test. Unlike the traditional Turing test, the judge of CAPTCHA must be a computer, so it is also called “reverse Turing test”.