Arcade · 1966

ELIZA

Joseph Weizenbaum's 1966 program, running the DOCTOR script printed with his paper. It plays a psychotherapist by spotting keywords and turning your words back into questions. Every reply here comes from the original script.

Show the rule behind each reply

On September 18, 1972, two programs talked over the ARPANET: PARRY, Kenneth Colby's simulation of a paranoid patient, running at Stanford, and a DOCTOR program running at BBN. Vint Cerf published the session as RFC 439. The italic notes are his.

Say something to ELIZA, then come back here to see how it chose its reply.

The DOCTOR script, as printed in 1966

(HOW DO YOU DO.  PLEASE TELL ME YOUR PROBLEM)

START

(SORRY
    ((0)
        (PLEASE DON'T APOLIGIZE)
        (APOLOGIES ARE NOT NECESSARY)
        (WHAT FEELINGS DO YOU HAVE WHEN YOU APOLOGIZE)
        (I'VE TOLD YOU THAT APOLOGIES ARE NOT REQUIRED)))

(DONT = DON'T)
(CANT = CAN'T)
(WONT = WON'T)

(REMEMBER 5
    ((0 YOU REMEMBER 0)
         (DO YOU OFTEN THINK OF 4)
         (DOES THINKING OF 4 BRING ANYTHING ELSE TO MIND)
         (WHAT ELSE DO YOU REMEMBER)
         (WHY DO YOU REMEMBER 4 JUST NOW)
         (WHAT IN THE PRESENT SITUATION REMINDS YOU OF 4)
         (WHAT IS THE CONNECTION BETWEEN ME AND 4))
    ((0 DO I REMEMBER 0)
         (DID YOU THINK I WOULD FORGET 5)
         (WHY DO YOU THINK I SHOULD RECALL 5 NOW)
         (WHAT ABOUT 5)
         (=WHAT)
         (YOU MENTIONED 5))
    ((0)
         (NEWKEY)))

(IF 3
    ((0 IF 0)
        (DO YOU THINK ITS LIKELY THAT 3)
        (DO YOU WISH THAT 3)
        (WHAT DO YOU THINK ABOUT 3)
        (REALLY, 2 3)))

(DREAMT 4
    ((0 YOU DREAMT 0)
        (REALLY, 4)
        (HAVE YOU EVER FANTASIED 4 WHILE YOU WERE AWAKE)
        (HAVE YOU DREAMT 4 BEFORE)
        (=DREAM)
        (NEWKEY)))

(DREAMED = DREAMT 4 (=DREAMT))

(DREAM 3
    ((0)
        (WHAT DOES THAT DREAM SUGGEST TO YOU)
        (DO YOU DREAM OFTEN)
        (WHAT PERSONS APPEAR IN YOUR DREAMS)
        (DON'T YOU BELIEVE THAT DREAM HAS SOMETHING TO DO WITH YOUR PROBLEM)
        (NEWKEY)))

(DREAMS = DREAM 3 (=DREAM))

(HOW (=WHAT))
(WHEN (=WHAT))
(ALIKE 10 (=DIT))
(SAME 10 (=DIT))
(CERTAINLY (=YES))

(FEEL DLIST(/BELIEF))
(THINK DLIST(/BELIEF))
(BELIEVE DLIST(/BELIEF))
(WISH DLIST(/BELIEF))

(MEMORY MY
    (0 YOUR 0 = LETS DISCUSS FURTHER WHY YOUR 3)
    (0 YOUR 0 = EARLIER YOU SAID YOUR 3)
    (0 YOUR 0 = BUT YOUR 3)
    (0 YOUR 0 = DOES THAT HAVE ANYTHING TO DO WITH THE FACT THAT YOUR 3))

(NONE
    ((0)
        (I AM NOT SURE I UNDERSTAND YOU FULLY)
        (PLEASE GO ON)
        (WHAT DOES THAT SUGGEST TO YOU)
        (DO YOU FEEL STRONGLY ABOUT DISCUSSING SUCH THINGS)))

(PERHAPS
    ((0)
        (YOU DON'T SEEM QUITE CERTAIN)
        (WHY THE UNCERTAIN TONE)
        (CAN'T YOU BE MORE POSITIVE)
        (YOU AREN'T SURE)
        (DON'T YOU KNOW)))

(MAYBE (=PERHAPS))

(NAME 15
    ((0)
        (I AM NOT INTERESTED IN NAMES)
        (I'VE TOLD YOU BEFORE, I DON'T CARE ABOUT NAMES - PLEASE CONTINUE)))

(DEUTSCH (=XFREMD))
(FRANCAIS (=XFREMD))
(ITALIANO (=XFREMD))
(ESPANOL (=XFREMD))

(XFREMD
    ((0)
        (I AM SORRY, I SPEAK ONLY ENGLISH)))

(HELLO
    ((0)
        (HOW DO YOU DO.  PLEASE STATE YOUR PROBLEM)))

(COMPUTER 50
    ((0)
        (DO COMPUTERS WORRY YOU)
        (WHY DO YOU MENTION COMPUTERS)
        (WHAT DO YOU THINK MACHINES HAVE TO DO WITH YOUR PROBLEM)
        (DON'T YOU THINK COMPUTERS CAN HELP PEOPLE)
        (WHAT ABOUT MACHINES WORRIES YOU)
        (WHAT DO YOU THINK ABOUT MACHINES)))

(MACHINE 50 (=COMPUTER))
(MACHINES 50 (=COMPUTER))
(COMPUTERS 50 (=COMPUTER))

(AM = ARE
    ((0 ARE YOU 0)
        (DO YOU BELIEVE YOU ARE 4)
        (WOULD YOU WANT TO BE 4)
        (YOU WISH I WOULD TELL YOU YOU ARE 4)
        (WHAT WOULD IT MEAN IF YOU WERE 4)
        (=WHAT))
    ((0)
        (WHY DO YOU SAY 'AM')
        (I DON'T UNDERSTAND THAT)))

(ARE
    ((0 ARE I 0)
        (WHY ARE YOU INTERESTED IN WHETHER I AM 4 OR NOT)
        (WOULD YOU PREFER IF I WEREN'T 4)
        (PERHAPS I AM 4 IN YOUR FANTASIES)
        (DO YOU SOMETIMES THINK I AM 4)
        (=WHAT))
    ((0 ARE 0)
        (DID YOU THINK THEY MIGHT NOT BE 3)
        (WOULD YOU LIKE IT IF THEY WERE NOT 3)
        (WHAT IF THEY WERE NOT 3)
        (POSSIBLY THEY ARE 3)))

(YOUR = MY
    ((0 MY 0)
        (WHY ARE YOU CONCERNED OVER MY 3)
        (WHAT ABOUT YOUR OWN 3)
        (ARE YOU WORRIED ABOUT SOMEONE ELSES 3)
        (REALLY, MY 3)))

(WAS 2
    ((0 WAS YOU 0)
        (WHAT IF YOU WERE 4)
        (DO YOU THINK YOU WERE 4)
        (WERE YOU 4)
        (WHAT WOULD IT MEAN IF YOU WERE 4)
        (WHAT DOES ' 4 ' SUGGEST TO YOU)
        (=WHAT))
    ((0 YOU WAS 0)
        (WERE YOU REALLY)
        (WHY DO YOU TELL ME YOU WERE 4 NOW)
        (PERHAPS I ALREADY KNEW YOU WERE 4))
    ((0 WAS I 0)
        (WOULD YOU LIKE TO BELIEVE I WAS 4)
        (WHAT SUGGESTS THAT I WAS 4)
        (WHAT DO YOU THINK)
        (PERHAPS I WAS 4)
        (WHAT IF I HAD BEEN 4))
    ((0)
        (NEWKEY)))

(WERE = WAS (=WAS))
(ME = YOU)

(YOU'RE = I'M
    ((0 I'M 0)
        (PRE (I ARE 3) (=YOU))))

(I'M = YOU'RE
    ((0 YOU'RE 0)
        (PRE (YOU ARE 3) (=I))))

(MYSELF = YOURSELF)
(YOURSELF = MYSELF)

(MOTHER DLIST(/NOUN FAMILY))
(MOM = MOTHER DLIST(/ FAMILY))
(DAD = FATHER DLIST(/ FAMILY))
(FATHER DLIST(/NOUN FAMILY))
(SISTER DLIST(/FAMILY))
(BROTHER DLIST(/FAMILY))
(WIFE DLIST(/FAMILY))
(CHILDREN DLIST(/FAMILY))

(I = YOU
    ((0 YOU (* WANT NEED) 0)
        (WHAT WOULD IT MEAN TO YOU IF YOU GOT 4)
        (WHY DO YOU WANT 4)
        (SUPPOSE YOU GOT 4 SOON)
        (WHAT IF YOU NEVER GOT 4)
        (WHAT WOULD GETTING 4 MEAN TO YOU)
        (WHAT DOES WANTING 4 HAVE TO DO WITH THIS DISCUSSION))
    ((0 YOU ARE 0 (*SAD UNHAPPY DEPRESSED SICK ) 0)
        (I AM SORRY TO HEAR YOU ARE 5)
        (DO YOU THINK COMING HERE WILL HELP YOU NOT TO BE 5)
        (I'M SURE ITS NOT PLEASANT TO BE 5)
        (CAN YOU EXPLAIN WHAT MADE YOU 5))
    ((0 YOU ARE 0 (*HAPPY ELATED GLAD BETTER) 0)
        (HOW HAVE I HELPED YOU TO BE 5)
        (HAS YOUR TREATMENT MADE YOU 5)
        (WHAT MAKES YOU 5 JUST NOW)
        (CAN YOU EXPLAIN WHY YOU ARE SUDDENLY 5))
    ((0 YOU WAS 0)
        (=WAS))
    ((0 YOU (/BELIEF) YOU 0)
        (DO YOU REALLY THINK SO)
        (BUT YOU ARE NOT SURE YOU 5)
        (DO YOU REALLY DOUBT YOU 5))
    ((0 YOU 0 (/BELIEF) 0 I 0)
        (=YOU))
    ((0 YOU ARE 0)
        (IS IT BECAUSE YOU ARE 4 THAT YOU CAME TO ME)
        (HOW LONG HAVE YOU BEEN 4)
        (DO YOU BELIEVE IT NORMAL TO BE 4)
        (DO YOU ENJOY BEING 4))
    ((0 YOU (* CAN'T CANNOT) 0)
        (HOW DO YOU KNOW YOU CAN'T 4)
        (HAVE YOU TRIED)
        (PERHAPS YOU COULD 4 NOW)
        (DO YOU REALLY WANT TO BE ABLE TO 4))
    ((0 YOU DON'T 0)
        (DON'T YOU REALLY 4)
        (WHY DON'T YOU 4)
        (DO YOU WISH TO BE ABLE TO 4)
        (DOES THAT TROUBLE YOU))
    ((0 YOU FEEL 0)
        (TELL ME MORE ABOUT SUCH FEELINGS)
        (DO YOU OFTEN FEEL 4)
        (DO YOU ENJOY FEELING 4)
        (OF WHAT DOES FEELING 4 REMIND YOU))
    ((0 YOU 0 I 0)
        (PERHAPS IN YOUR FANTASY WE 3 EACH OTHER)
        (DO YOU WISH TO 3 ME)
        (YOU SEEM TO NEED TO 3 ME)
        (DO YOU 3 ANYONE ELSE))
    ((0)
        (YOU SAY 1)
        (CAN YOU ELABORATE ON THAT)
        (DO YOU SAY 1 FOR SOME SPECIAL REASON)
        (THAT'S QUITE INTERESTING)))

(YOU = I
    ((0 I REMIND YOU OF 0)
        (=DIT))
    ((0 I ARE 0)
        (WHAT MAKES YOU THINK I AM 4)
        (DOES IT PLEASE YOU TO BELIEVE I AM 4)
        (DO YOU SOMETIMES WISH YOU WERE 4)
        (PERHAPS YOU WOULD LIKE TO BE 4))
    ((0 I 0 YOU)
        (WHY DO YOU THINK I 3 YOU)
        (YOU LIKE TO THINK I 3 YOU - DON'T YOU)
        (WHAT MAKES YOU THINK I 3 YOU)
        (REALLY, I 3 YOU)
        (DO YOU WISH TO BELIEVE I 3 YOU)
        (SUPPOSE I DID 3 YOU - WHAT WOULD THAT MEAN)
        (DOES SOMEONE ELSE BELIEVE I 3 YOU))
    ((0 I 0)
        (WE WERE DISCUSSING YOU - NOT ME)
        (OH, I 3)
        (YOU'RE NOT REALLY TALKING ABOUT ME - ARE YOU)
        (WHAT ARE YOUR FEELINGS NOW)))

(YES
    ((0)
        (YOU SEEM QUITE POSITIVE)
        (YOU ARE SURE)
        (I SEE)
        (I UNDERSTAND)))

(NO
    ((0)
        (ARE YOU SAYING 'NO' JUST TO BE NEGATIVE)
        (YOU ARE BEING A BIT NEGATIVE)
        (WHY NOT)
        (WHY 'NO')))

(MY = YOUR 2
    ((0 YOUR 0 (/FAMILY) 0)
        (TELL ME MORE ABOUT YOUR FAMILY)
        (WHO ELSE IN YOUR FAMILY 5)
        (YOUR 4)
        (WHAT ELSE COMES TO MIND WHEN YOU THINK OF YOUR 4))
    ((0 YOUR 0)
        (YOUR 3)
        (WHY DO YOU SAY YOUR 3)
        (DOES THAT SUGGEST ANYTHING ELSE WHICH BELONGS TO YOU)
        (IS IT IMPORTANT TO YOU THAT 2 3)))

(CAN
    ((0 CAN I 0)
        (YOU BELIEVE I CAN 4 DON'T YOU)
        (=WHAT)
        (YOU WANT ME TO BE ABLE TO 4)
        (PERHAPS YOU WOULD LIKE TO BE ABLE TO 4 YOURSELF))
    ((0 CAN YOU 0)
        (WHETHER OR NOT YOU CAN 4 DEPENDS ON YOU MORE THAN ON ME)
        (DO YOU WANT TO BE ABLE TO 4)
        (PERHAPS YOU DON'T WANT TO 4)
        (=WHAT)))

(WHAT
    ((0)
        (WHY DO YOU ASK)
        (DOES THAT QUESTION INTEREST YOU)
        (WHAT IS IT YOU REALLY WANT TO KNOW)
        (ARE SUCH QUESTIONS MUCH ON YOUR MIND)
        (WHAT ANSWER WOULD PLEASE YOU MOST)
        (WHAT DO YOU THINK)
        (WHAT COMES TO YOUR MIND WHEN YOU ASK THAT)
        (HAVE YOU ASKED SUCH QUESTIONS BEFORE)
        (HAVE YOU ASKED ANYONE ELSE)))

(BECAUSE
    ((0)
        (IS THAT THE REAL REASON)
        (DON'T ANY OTHER REASONS COME TO MIND)
        (DOES THAT REASON SEEM TO EXPLAIN ANYTHING ELSE)
        (WHAT OTHER REASONS MIGHT THERE BE)))

(WHY
    ((0 WHY DON'T I 0)
        (DO YOU BELIEVE I DON'T 5)
        (PERHAPS I WILL 5 IN GOOD TIME)
        (SHOULD YOU 5 YOURSELF)
        (YOU WANT ME TO 5)
        (=WHAT))
    ((0 WHY CAN'T YOU 0)
        (DO YOU THINK YOU SHOULD BE ABLE TO 5)
        (DO YOU WANT TO BE ABLE TO 5)
        (DO YOU BELIEVE THIS WILL HELP YOU TO 5)
        (HAVE YOU ANY IDEA WHY YOU CAN'T 5)
        (=WHAT))
    (=WHAT))

(EVERYONE 2
    ((0 (* EVERYONE EVERYBODY NOBODY NOONE) 0)
        (REALLY, 2)
        (SURELY NOT 2)
        (CAN YOU THINK OF ANYONE IN PARTICULAR)
        (WHO, FOR EXAMPLE)
        (YOU ARE THINKING OF A VERY SPECIAL PERSON)
        (WHO, MAY I ASK)
        (SOMEONE SPECIAL PERHAPS)
        (YOU HAVE A PARTICULAR PERSON IN MIND, DON'T YOU)
        (WHO DO YOU THINK YOU'RE TALKING ABOUT)))

(EVERYBODY 2 (= EVERYONE))
(NOBODY 2 (= EVERYONE))
(NOONE 2 (= EVERYONE))

(ALWAYS 1
    ((0)
        (CAN YOU THINK OF A SPECIFIC EXAMPLE)
        (WHEN)
        (WHAT INCIDENT ARE YOU THINKING OF)
        (REALLY, ALWAYS)))

(LIKE 10
    ((0 (*AM IS ARE WAS) 0 LIKE 0)
        (=DIT))
    ((0)
        (NEWKEY)))

(DIT
    ((0)
        (IN WHAT WAY)
        (WHAT RESEMBLANCE DO YOU SEE)
        (WHAT DOES THAT SIMILARITY SUGGEST TO YOU)
        (WHAT OTHER CONNECTIONS DO YOU SEE)
        (WHAT DO YOU SUPPOSE THAT RESEMBLANCE MEANS)
        (WHAT IS THE CONNECTION, DO YOU SUPPOSE)
        (COULD THERE REALLY BE SOME CONNECTION)
        (HOW)))

()

How ELIZA works

Keywords. ELIZA scans what you type for words the script knows, such as MOTHER, DREAM or COMPUTER. Each has a priority, and the highest wins.
Patterns. Each keyword has patterns like (0 YOU ARE 0 (*SAD UNHAPPY DEPRESSED) 0), where 0 means "any words". A match splits your sentence into numbered parts.
Reassembly. A reply such as (I AM SORRY TO HEAR YOU ARE 5) rebuilds the sentence from those parts, after swapping I for YOU and MY for YOUR. Replies for the same pattern are used in turn.
Memory. When you mention something of yours, ELIZA may file it away and bring it back later, when you say something it has no rule for.
Only the first clause with a keyword counts: ELIZA stops at a comma, a period or BUT. Turn on Show the rule to watch all of this happen.

History

Joseph Weizenbaum wrote ELIZA at MIT between 1964 and 1966 on the IBM 7094 time-sharing system, in his own list-processing language, MAD-SLIP.¹² He described it in "ELIZA—A Computer Program for the Study of Natural Language Communication Between Man and Machine" (Communications of the ACM 9, no. 1, January 1966).² The program was general; its behavior came from a script, and the DOCTOR script, which imitates a Rogerian psychotherapist, became the famous one.²¹

People took to it quickly, and some confided in it as if it understood them.¹ That reaction troubled Weizenbaum.¹ In Computer Power and Human Reason (1976) he argued that some decisions should never be left to computers, whatever they can be made to do.¹

The 1966 paper printed the DOCTOR script but not the program.²³ A printout of Weizenbaum's original code was found in his papers at MIT in 2021 by Jeff Shrager and MIT archivist Myles Crowley,³ which is how we know, for example, that ELIZA also treated BUT as a delimiter and chose its MEMORY replies by a hash, not at random as the 1966 paper said.⁴² Sixty years on, ELIZA is usually called the first chatbot.³ For what changed between pattern matching and today's language models, see From Shannon's bits to Claude's tokens and the AI resources.

Sources

1Joseph Weizenbaum, Computer Power and Human Reason: From Judgment to Calculation (San Francisco: W. H. Freeman, 1976). Cited at pages 2, 3–5, 6–7, 7, 11–13.
2Joseph Weizenbaum, “ELIZA—A Computer Program for the Study of Natural Language Communication Between Man and Machine,” Communications of the ACM 9, no. 1 (January 1966): 36–45, https://doi.org/10.1145/365153.365168. Cited at pages 36, 37, 41, 44–45.
3Rupert Lane, Anthony Hay, Arthur Schwarz, David M. Berry, and Jeff Shrager, “ELIZA Reanimated: The world's first chatbot restored on the world's first time sharing system” (preprint, arXiv, January 12, 2025), https://doi.org/10.48550/arXiv.2501.06707.
4Joseph Weizenbaum (transcribed by Anthony Hay, Arthur Schwarz, and Rupert Lane), “eliza.mad (transcription of the 1965 MAD-SLIP ELIZA printout),” eliza-ctss, 1965, https://raw.githubusercontent.com/rupertl/eliza-ctss/main/eliza/src/ELIZA/eliza.mad (accessed October 26, 2026).

About this version and sources

This is a new TypeScript program that reads the DOCTOR script exactly as it was printed in the paper's appendix, using Anthony Hay's verbatim transcription (released under CC0). It follows the details of Weizenbaum's MAD-SLIP code that Hay documented, and it reproduces the paper's sample conversation, from "Men are all alike" to "Bullies", word for word; that conversation is one of its tests. One printed line differs: the paper shows "WHAT ELSE COMES TO YOUR MIND", while the script in the same paper says "COMES TO MIND", and this follows the script. "APOLIGIZE" is the script's own spelling.

The 1972 conversation is reproduced from RFC 439. That DOCTOR was a later version running at BBN, not Weizenbaum's MIT program, which is why some of its replies differ from this one's.

J. Weizenbaum, "ELIZA," Communications of the ACM 9(1):36–45, 1966. doi:10.1145/365153.365168
J. Weizenbaum, Computer Power and Human Reason, W. H. Freeman, 1976.
V. Cerf, RFC 439: PARRY Encounters the DOCTOR, January 1973.
ELIZA archaeology project, elizagen.org.
A. Hay, A simulation of Weizenbaum's 1966 ELIZA (CC0).