Joseph Weizenbaum’s 1966 computer program that simulated a psychotherapist was called ELIZA.
Weizenbaum created ELIZA at MIT using the MAD-SLIP programming language. Its best-known script, DOCTOR, imitated a Rogerian therapist by reflecting users’ statements back as questions. For example, a statement about family might prompt ELIZA to ask the user to say more about family relationships.
ELIZA did not understand language in the modern sense. It used pattern matching and substitution rules to identify keywords and generate replies. Even so, some users attributed human-like understanding to it, a reaction that helped inspire later discussions about conversational software and artificial intelligence.
ELIZA is often confused with PARRY, a later program designed to model a person with paranoid delusions. ELIZA was not a voice assistant or a machine-learning model; its responses were primarily hand-authored rules.