Joseph Weizenbaum's ELIZA used simple pattern matching to simulate a Rogerian psychotherapist. It understood nothing — yet people confided their deepest problems to it. His own secretary asked him to leave the room for privacy. Try it yourself, then see how it works.
ELIZA — MIT AI Lab, 1966
ELIZA Rogerian Therapist Simulation Based on Joseph Weizenbaum's original 1966 program Type a message and press Enter to begin. ─────────────────────────────────────
Hello. I am ELIZA. How are you feeling today?
How ELIZA works: Each response is generated by scanning your input for keywords, decomposing the sentence with a pattern, then reassembling it as a question. Click the ▶ Pattern Match labels to see exactly which rule fired and how your words were transformed. ELIZA has no memory, no understanding, and no model of the world — just ~50 text substitution rules. The fact that it feels like a real conversation is the ELIZA effect.