~t such a
)lained . i.
teal at _1[
~94. Its n~
ion that ii
in fact off:
~ber of us
o the 0vei
se it, is b:.:
) svstera. ~
• ~LIZA i?:
J tl tl u arv;[ I:
it'~ ~=~e. !. ant tmhappy.
i)() ~ 0U TitlNK COMING IIERE WILl, IiELP YOU NOT TO
>cod some help, tidal m,,teh seems certain.
"G'I~AT WOL'I,D IT MEAN TO YOU IF YOU GOT SOME IIELP
l'c, ri~ ps I could learn ~o get ahmgv, ith my mother.
MORE ABOUT YOUE FAMILY
),[5" -mnher takes care of me,
WiI() EI,SE IN ¥0UR FAMILY TAKES CAiIE 0F YOU
5-,)u are like my father in some ways.
WiIAT RESEMBLANCE DO YOU SEE
You are not vet',," aggressive but 1 think you don't wa.t~.t me to
WHAT MAKES YOU TttINK I AM NOT VER~ AGGRESSIVE
argue with me.
WIlY 1)O YOU THINK
DON'T ARGUE WITH YOU
"~-(}u are afraid of me,
DOES iT PLEASE YOU TO BEI, IE\'E I AM AFRA[I) OF YOU
My far her is afraid of everybody.
WHAT ELSE COMES TO MIND WtIEN YOU THINK OF
DOES THAT HA\-E ANYTtIING TO DO WITH THE FACT
TItAT YOUR BOYFR IENI) MADE YOU COME HERE
The capitalized lines are the machine responses.
The gross procedure of the program is quite simple; the
text: is read and inspected for the presence of a
if such a word is found, the sentence is transformed
according to a
associated with the keyword, if not a
content-free renmrk or, under certain conditions, an earlier
transformation is retrieved. The text so computed or
retrieved is then printed out.
In detail, of course, the procedure sketched above is
considerably more complex. Keywords, for example, amy
have a RAXK or precedence number. The procedure is
sensitive to such numbers in that it will abandon a key-
word a.lready found in the left-to-right scan of the text in
fxvor of one having a higher rank. Also, the procedure
reeo~,afizes a comma or a period as a delimiter. Whenever
either one is encountered and a keyword has already been
found, all snbsequent text is deleted from the input mes-
sage. If no key had yet been found the phrase or sentence
to the left• of the delimiter (as well as the delimiter itself)
is deleted. As a result•, only single phrases or sentences are
I£eywords and their associated transformation t rules
constitute the SCRIPT for a particular class of con-
versation. An important property of ELIZA is that a
script is data; i.e., it is not part of the program itself.
Hence, ELIZA is not restricted to a particular set of
recognition patterns or responses, indeed not even to any
specific language. ELIZA scripts exist (at, this writing) in
Welsh attd Gernmn as well as in English.
The fundamental technical problems with which ELIZA
must be preoccupied are the following:
(1) The identification of the "most important" keyword
The word "transformation" is used in its generic sense rather
than that given it by tia.rris and Chomsky in linguistic contexts.
V(~lume 9 /Numher 1 / January, 1966
occurring in the input message.
(2) Tile identification of some minimal context within
which the chosen keyword at)pears; e.g., if the keyword is
is it followed by the word "are" (in which ease an
assertion is probably being made).
(3) The choice of an appropriate transformation rule
and, of course, the making of the transformation itself.
(4) The provision of mechanism that will permit
ELIZA to respond
when the input text
contained no keywords.
(5) The provision of machinery that facilitates editing,
particularly extension, of the script on the script writing
There are, of course, the usual constraints dictated by
the need to be eeononfical in the use of computer time and
The central issue is clearly one of text manipulation,
and at the heart of that issue is the concept of the
which has been said to be associated with
certain keywords. The meehanisins subsumed under the
sloga.n "transformation rule" are a number of SLIP func-
tions which serve to (1) decompose a data string according
to certain criteria, hence to test the string as to whether it
satisfies these criteria or not, and (2) to reassemble a
decomposed string according to certain assembly specifica-
While this is not the i)lace to discuss these functions in
all their detail (or even to reveal their full power and
generality), it is important to the understanding of the
operation of ELIZA to describe them in
Consider the sentence "I ant very unhappy these days".
Suppose a foreigner with only a limited knowledge of
English but with a veer good ear heard that sentence
spoken but understood only the first two words "I am".
Wishing to appear interested, perhaps even sympathetic,
he may reply "How long have you been very unhappy
these days?" What he nmst have done is to apply a kind
of template to the original sentence, one part of which
matched the two words "I aln" and the remainder isolated
the words "very unhat)py these days". He must also have
a reassembly kit specifically associated with that template,
one that specifies that any sentence of the form "I am
BLAH" can be transformed to "How long have you been
BLAH", independently of the meaning of BLAH. A
somewhat more complicated example is given by the
sentence "It seems that you hate me". Here the foreigner
understands only the words "you" and "me"; i.e., he
applies a template that decomposes the sentence into the
(1) It seems that (2) you (3) hate (4) me
of which only the second and fourth parts are understood.
The reassembly rule might then be "What makes you
think I hate you"; i.e., it nfight throw away the first
component, translate the two known words ("you" to
to "you") and tack on a stock phrase
(What makes you think) to the front of the reconstruction.