The versions
There was never one ELIZA. The project documents at least five major versions between 1965 and 1968, each with distinct capabilities, and some likely lost for good. ELIZA is better understood as a multiplicity than as a single object.
- 1965aearliest
Uses only “.” and “,” to break input into sentences.
- 1965brecovered source
Adds “but” as a delimiter; lacks the NEWKEY function. This is the version whose printout we recovered, and the basis for the close reading on this site.
- 1966CACM
The version described in Weizenbaum’s Communications of the ACM paper. Introduces the NEWKEY function and a keyword stack, enabling more contextual memory.
- 1967OPL
Sophisticated script handling: evaluators allowing expressions of unlimited complexity, and a generalised script system.
- 1968+platform
Multiple simultaneous scripts, inter-script communication, and dynamic editing. Used for computer-assisted education at MIT and Harvard. No source for this version has yet been found.
Beyond DOCTOR
The archive holds evidence of scripts well beyond the Rogerian therapist: ARITHM for mathematics tutoring, YAPYAP for psychiatric research at Massachusetts General Hospital, SPACKS engaging Barry Spacks’s poetry about Belsen, and even a Nixon parody. Weizenbaum built ELIZA into a family of programs whose use has been largely forgotten. The plurality of ELIZA ›
Despite extensive archival work, no source survives for ELIZA’s sophisticated later versions. The OPL-based multi-script platform deployed in classrooms has simply disappeared, leaving only fragments in Project MAC progress reports. The tragedy is not only the missing code, but the absence of the institutional habits that would have preserved it. Version variation ›