Finding ELIZA

Sun, 06 Jun 2021 00:59:57 GMT

Note: Despite being posted on a Saturday and a title that includes the name of a a character from a well-known musical, this is not a Songs for Saturday post. It doesn't have anything to do with fish, either.

Remarkably, Joseph Weizenbaum's original source code for ELIZA has been rediscovered, after having been missing and believed lost for over half a century, and was made public on May 23rd of this year. ELIZA is probably the oldest and almost certainly the best-known implementation of what is now known as a chatbot.

If you decide to look at the code, start by reading the web page it's embedded in before you dive into the listing. The "Notes on reading the code" section, which comes after the listing, will prevent a lot of confusion. The listing itself is a scan of a 132-column listing, and definitely benefits from being viewed full-screen on a large monitor.

The first thing you see in the listing is the script -- the set of rules that tells the ELIZA program how to respond to input. The program itself starts on page 6. You might be misled by the rules, which are in the form of parenthesized lists, into thinking that the program would be written in LISP. It's not; it's written in MAD, an Algol-like language, with Weisenbaum's SLIP (Symmetric List Processing) primitives embedded in it.

SLIP uses circular, bidirectionally-linked lists. Each list has a header with pointers to the first and last list element; the header of an empty list points to itself. I've lost track of how many times I've implemented doubly-linked lists, in everything from assembly language to Java.

ELIZA is the name of the program, but "Eliza" usually refers to the combination of an Eliza-like program with the Doctor script. The most common script is a (rather poor) simulation of a Rogerian psychotherapist called "Doctor". According to the note at the bottom of the Original Eliza page, actual Rogerian therapists have pronounced it a perfect example of how not to do Rogerian therapy. Nevertheless, many people are said to have been helped by ELIZA, and it's possible to have a surprisingly intimate conversation with her as long as you suspend your disbelief and respect her limits.

If you have Emacs installed on your computer, you can access a version of Doctor with M-X doctor. Otherwise, browse to Eliza, Computer Therapist if you don't mind having a potentially intimate conversation with something hosted on a public website. (Or simply download the page -- it's written in Javascript.)

Resources

ELIZAGEN -- The Genealogy of ELIZA "This site is dedicated to tracing the legacy ofJoseph Weizenbaum's ELIZA (aka. Doctor) program."
ELIZAGEN - The Original ELIZA - the source code.
anthay/ELIZA: A Simulation in C++ of Joseph Weizenbaum’s 1966 ELIZA by Anthony Hay. The README includes both a copy of the transcript published in Wizenbaum's CACM article in 1966, and a detailed description of the script syntax and how it works.
MAD (Michigan Algorithm Decoder) manual by Elliott Organick (1961).
GNU gSlip [PDF Manual(738K)] for C++.
doctor.el\play\lisp - emacs.git - Emacs source repository - the Doctor program as implemented in Emacs LISP.
Eliza, Computer Therapist in Javascript

Another fine post from The Computer Curmudgeon (also at computer-curmudgeon.com).
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