Decoding ELIZA: How the First Chatbot’s Source Code Revealed Hidden Personalities

A deep dive into the rediscovered source code of ELIZA, the world’s first chatbot created by Joseph Weizenbaum at MIT in the 1960s, has revealed unexpected complexity. While often dismissed as a simple pattern-matching program, the code demonstrates a sophisticated architecture capable of supporting multiple conversational “scripts.” This structure shows that ELIZA was designed with more flexibility than previously understood by modern researchers.

Beyond the famous “DOCTOR” persona, the analysis highlights how early computer scientists experimented with the psychological boundaries of human-machine interaction. These hidden lessons from ELIZA’s code provide a unique lens through which to view current generative AI developments, reminding us that the challenges of conversational AI—such as user projection and ethical boundaries—have been present since the very beginning of the field.