Eliza is an interactive dialog program, written in the 1960's by Joseph Weizenbaum. The best-known version made Eliza emulate a Rogerian ("nondirective") psychoanalyst. Sample dialog: Men are all alike. IN WHAT WAY They're always bugging us about something or another. CAN YOU BE MORE SPECIFIC Well, my boyfriend made me come here. YOUR BOYFRIEND MADE YOU COME HERE He says I'm depressed much of the time. I AM SORRY TO HEAR YOU ARE DEPRESSED It's true. I am unhappy. DO YOU THINK COMING HERE WILL HELP YOU NOT TO BE UNHAPPY I need some help, that much seems certain. WHAT WOULD IT MEAN TO YOU IF YOU GOT SOME HELP Perhaps I could learn to get along with my mother. TELL ME MORE ABOUT YOUR FAMILY Another dialog program, Parry, was written by Dr. Kenneth Colby to mimic paranoid behavior. The following is part of a dialog between Eliza and Parry: I don't understand your motives. WHY DON'T YOU UNDERSTAND MY MOTIVES? Shouldn't I be? WHY DID YOU SAY THAT JUST NOW? That's just the way it is. SUPPOSE THAT'S JUST THE WAY IT WERE NOT. So? I'M NOT SURE I UNDERSTAND YOU FULLY. You harp on the same questions too much. WHAT DOES THAT SIMILARITY SUGGEST TO YOU? I don't get you. DO YOU WISH THAT YOU DID GET I? The moral, according to Norvig: This suggests that neither Eliza nor Parry had a deep understanding of the dialog. When there is a human to take on most of the burden of carrying forth the conversation, these programs can be convincing, but when the human is taken out of the conversation, the weaknesses of the programs are revealed. The whole "trick" of Eliza is to recognize PATTERNS in the input, and to use those patterns to generate responses.