ELIZA was the 1966 chatbot created by Joseph Weizenbaum at MIT.
Weizenbaum developed ELIZA as a computer program that simulated conversation by matching patterns in a user’s typed statements and transforming them into replies. Its best-known script, DOCTOR, imitated a Rogerian psychotherapist by reflecting users’ words back as questions, such as asking what led someone to make a particular statement.
ELIZA did not understand language in the modern sense. It used rules, keywords, and templates rather than a learned model of the world. Nevertheless, some users attributed more understanding to it than the program possessed, a reaction that influenced later discussions about human responses to conversational machines. The phenomenon is now often called the ELIZA effect: people may unconsciously treat a computer’s language behavior as evidence of understanding, even when its underlying mechanism is simple pattern processing.