In 1966, MIT Joseph Weizenbaum created one of the earliest natural-language processing programs, called ELIZA.
ELIZA was capable of participating in simple conversations with humans. For example:
ELIZA: How do you do. Please state your problem.
HUMAN: I spend too much time with computers.
ELIZA: Why do you mention computers?
HUMAN: You are one.
ELIZA: Does it please you to believe I am one?
ELIZA: You seem to be quite positive.
HUMAN: I suppose I am.
The main purpose of ELIZA wasn't to demonstrate artificial intelligence, according to artificial intelligence expert and Stanford University computer science professor emeritus Nils Nilsson.
"Weizenbaum didn't really write [ELIZA] to answer questions," Nilsson said. "He just wanted to show how easily humans could be fooled into thinking that the program was intelligent."
Today, the Watson computer’s success at feigning intelligence stems largely from its a natural-language processing program, DeepQA—the computer’s “most useful software,” according to PC World. DeepQA enables Watson to understand typical Jeopardy! questions and respond, well, naturally.
Richard Doherty, research director at the Envisioneering Group technology consulting firm, told Computerworld that "this is the largest [computing] advancement in decades. This isn't an iPad. To reach [a computer] conversationally and have it respond with knowledgeable answers is a sea change in computing."
(See why some think artificial intelligence may offer humans electronic immortality.)
Source of ELIZA transcript: The Quest for Artificial Intelligence by Nils J. Nilsson.