ELIZA — The First Chatbot

In 1966, MIT computer scientist Joseph Weizenbaum created ELIZA, a natural language processing program that simulated conversation by using pattern matching and substitution rules. Its most famous script, DOCTOR, mimicked a Rogerian psychotherapist by turning the user's statements into questions ("I feel sad" became "Why do you feel sad?"). Weizenbaum was disturbed to discover that users — including his own secretary — became deeply emotionally engaged with the program, treating it as a genuine therapist despite knowing it was a machine. He wrote Computer Power and Human Reason (1976) warning against anthropomorphizing machines. ELIZA became the ancestor of every chatbot, from SmarterChild to Siri to ChatGPT, and demonstrated what is now called the "ELIZA effect" — the human tendency to attribute understanding to computers.