Alan Turing, a british mathematecian, scientist more importantly considered as "Father of Computer Science".
He visulaised (like our hollywood) the 'rise of the machines' in the future - so, he devised a test to differentiate between a man and a machine. It is now termed as the famous "Turing Test".
The test was inspired by a party game known as the "Imitation Game", in which a man and a woman go into separate rooms, and guests try to tell them apart by writing a series of questions and reading the typewritten answers sent back. In this game, both the man and the woman aim to convince the guests that they are the woman.
Ok, now we are using daily. the variants of these "Turing Tests". Wonder? Have you registered for some websites where it asks to read a distorted image and type in the letters? That's a captcha (an acronym for "completely automated public Turing test to tell computers and humans apart"). That is based on the assumptions that a computer can not recognise and deciphere the distorted image as we do.
If you are interetsted in reading about other types of tests based on video (Gimpy), common pattern (Bongo), and sound (Sounds) - You can read them in http://en.wikipedia.org/wiki/Turing_test.
Thanks for reading!