Essays
1. Would you consider something to be intelligent if it could hold a
conversation with you? Discuss with reference to ELIZA or PARRY, and
the Turing and Loebner tests.
2. Discuss the extent to which Artificial Intelligence has increased, or
changed, our understanding of what it means to be intelligent.
3. Consider the following; expert systems, PARRY, SAM (Script Applier
Mechanism). With reference to the Chinese Room argument, discuss
the extent to which each of them can be said to understand the world.
4. Discuss the relationship between the arguments made by Turing about
the Turing Test, and by Searle about the Chinese Room.
5. Discuss the plausibility of a Language of Thought as a representation
system in the brain and what its relationship to AI could or should be.
6. Describe how you would design a computer conversationalist (perhaps
like CONVERSE) and what conversational abilities you would hope to
put in it, linking these to possible processes as far as you can.
COM1070: Introduction to
Artificial Intelligence: week 4
Yorick Wilks
Computer Science Department
University of Sheffield
www.dcs.shef.ac.uk/-yorick
Arguments about meaning and
understanding (and programs)
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Searle’s Chinese Room argument
The Symbol Grounding argument
Bar-Hillel’s argument about the
impossibility of machine translation
Searle’s Example
The Chinese Room
An operator O. sits in a room; Chinese
symbols come in which O. does not
understand. He has explicit instructions (a
program!) in English in how to get an output
stream of Chinese characters from all this,
so as to generate “answers” from
“questions”. But of course he understands
nothing even though Chinese speakers who
see the output find it correct and
indistinguishable from the real thing.
The Chinese Room
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Read chapter 6 in Copeland (1993):
The curious case of the Chinese Room.
Clearer account: pgs 292-297 in
Sharples, Hogg, Hutchinson, Torrance
and Young (1989) ‘Computers and
Thought’ MIT Press: Bradford Books.
Original source: Minds, Brains and
Programs: John Searle (1980)
Important philosophical critic of Artificial
Intelligence. See also more recent
book:
Searle, J.R. (1997) The Mystery of
Consciousness. Granta Books, London
Weak AI: computer is valuable tool for
study of mind, ie can formulate and test
hypotheses rigorously.
Strong AI: appropriately programmed
computer really is a mind, can be said to
understand, and has other cognitive
states.
Searle is an opponent of strong AI, and
the Chinese room is meant to show
what strong AI is, and why it is wrong.
It is an imaginary Gedankenexperiment
like the Turing Test.
Can digital computers think?
Could take this as an empirical argument
- wait and see if AI researchers manage
to produce a machine that thinks.
Empirical means something which can be
settled by experimentation and
evidence gathering.
Example of empirical question:
Are all ophthalmologists in New York over
25 years of age?
Example of non-empirical question:
are all ophthalmologists in New York eye
specialists?
Searle - ‘can a machine think’ is not an
empirical question. Something following
a program could never think, says S.
Contrast this with Turing, who believed:
‘Can machines think?’ was better seen as
a practical/empirical question, so as to
avoid the philosophy (it didn’t work!).
Back into the Chinese Room
|Operator in room with pieces of paper.
Symbols written on paper which operator
cannot understand.
Slots in wall of room - paper can come in
and be passed out.
Operator has set of rules telling him/her
how to build, compare and manipulate
symbol-structures using pieces of paper
in room, together with those passed in
from outside.
Example of rule:
if the Input slot pattern is XYZ, write that
on the next empty line of the exercise
book labelled ‘Input store’
transform this into sets of bits (say,
1001001111), then perform specified set
of manipulations on those bits (giving
another bit string).
then pair this result with Chinese
characters, put in ‘Output store’ and
push through Output slot.
But symbols mean nothing to operator.
Instructions correspond to program which
simulates linguistic ability and
understanding of native speaker of
Chinese.
Sets of symbols passed in and out
correspond to sentences of meaningful
dialogue.
More than this: Chinese Room program is
(perhaps!) able to pass the Turing Test
with flying colours!
According to Searle, behaviour of
operator is like that of computer running
a program. What point do you think
Searle is trying to make with this
example?
Searle: Operator does not understand
Chinese - only understands instructions
for manipulating symbols.
Behaviour of operator is like behaviour of
computer running same program.
Computer running program does not
understand any more than the operator
does.
Searle: operator only needs syntax, not
semantics.
Semantics - relating symbols to real
world.
Syntax - knowledge of formal properties
of symbols (how they can be
combined).
Mastery of syntax: mastery of set of rules
for performing symbol manipulations.
Mastery of semantics: to have
understanding of what those symbols
mean (this is the hard bit!!)
Example: from Copeland.
Arabic sentence
Jamal hamati indaha waja midah
2 syntax rules for arabic:
a) To form the I-sentence corresponding
to a given sentence, prefix the whole
sentence with the symbols ‘Hal’
b) To form the N-sentence corresponding
to any reduplicative sentence, insert the
particle ‘laysa’ in front of the predicate
of the sentence.
What would I sentence and N sentence
corresponding to Arabic sentence be.
(sentence is reduplicative and its
predicate consists of everything
following ‘hamati’)?
Jamal hamati indaha waja midah
But syntax rules tell us nothing about the
semantics. Hal forms an interrogative,
and laysa forms a negation. Question
asks whether your mother-in-law’s
camel has belly ache:
Hal jamal hamati indaha waja midah
and second sentence answers in the
negative:
Laysa indaha waja midah
According to Searle, computers just
engaging in syntactical manoeuvres like
this.
Remember back to PARRY
PARRY was not designed to show
understanding, but was often thought to
do so. We know it worked with a very
simple but large mechanism:
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Why are you in the hospital?
I SHOULDN’T BE HERE.
Who brought you here?
THE POLICE.
What trouble did you have with the police?
COPS DON’T DO THEIR JOB.
Strong AI: Machine can literally be said to
understand the responses it makes.
Searle’s argument is that like the
operator in the Chinese Room,
PARRY’s computer does not
understand anything it responds--which
is certainly true of PARRY but is it true
in principle, as Searle wants?
Searle: Program carries out certain
operations in response to its input, and
produces certain outputs, which are
correct responses to questions.
But hasn’t understood a question any
more than an operator in the Chinese
Room would have understood Chinese.
Questions: is Searle’s argument
convincing?
Does it capture some of your doubts
about computer programs?
Suppose for a moment Turing had
believed in Strong AI. He might have
argued:
a computer succeeding in the imitation
game will have same mental states that
would have been attributed to human.
Eg understanding the words of the
language been used to communicate.
But, says Searle. the operator cannot
understand Chinese.
Treat the Chinese Room system as a
black box and ask it (in Chinese) if it
understands Chinese “Of course I do”
Ask operator (if you can reach them!) if
he/she understands Chinese “search me, its just a bunch of
meaningless squiggles”.
Responses to Searle:
1. Insist that the operator can in fact
understand Chinese Like case in which person plays chess
who does not know rules of chess but is
operating under post-hypnotic
suggestion.
Compare blind-sight subjects who can
see but do not agree they can---consciousness of knowledge may be
irrelevant here!
2. Systems Response (so called by
Searle)
concede that the operator does not
understand Chinese, but that system as
a whole, of which operator is a part,
DOES understand Chinese.
Copeland: Searle makes an invalid
argument (operator = Joe)
Premiss - No amount of symbol
manipulation on Joe’s part will enable
Joe to understand the Chinese input.
Therefore No amount of symbol
manipulation on Joe’s part will enable
the wider system of which Joe is a
component to understand the Chinese
input.
Burlesque of the same thing clearly
doesn’t follow.
Premiss: Bill the cleaner has never sold
pyjamas to Korea.
Therefore the company for which Bill
works has never sold pyjamas to Korea.
Searle’s rebuttal of systems reply: if
symbol operator doesn’t understand
Chinese, why should you be able to say
that symbol operator (Joe) plus bits of
paper plus room understands Chinese.
System as a whole behaves as though it
understands Chinese. But that doesn’t
mean that it does.
Recent restatement of Chinese Room
Argument
From Searle (1997) The Mystery of
Consciousness
1. Programs are entirely syntactical
2. Minds have a semantics
3. Syntax is not the same as, nor by itself
sufficient for, semantics
Therefore programs are not minds. QED
Step 1: - just states that a program written
down consists entirely of rules
concerning syntactical entities, that is
rules for manipulating symbols. Physics
of implementing medium (ie computer)
is irrelevant to computation.
Step 2: - just says what we know about
human thinking. When we think in
words or other symbols we have to
know what those words mean - a mind
has more than uninterpreted formal
symbols running through it, it has
mental contents or semantic contents.
Step 3: - states the general principle that
Chinese Room thought experiment
illustrates. Merely manipulating formal
symbols does not guarantee presence
of semantic contents.
‘..It does not matter how well the system
can imitate the behaviour of someone
who really does understand, nor how
complex the symbol manipulations are;
you can not milk semantics out of
syntactical processes alone..’
(Searle, 1997)
The Internalised Case
Suppose the operator learns up all these rules
and table and can do the trick in Chinese.
On this version, the Chinese Room has
nothing in but the operator.
Can one still say the operator understands
nothing of Chinese?
Consider: a man appears to speak French
fluently but say, no he doesn’t really, he’s
just learned up a phrase book. He’s joking,
isn’t he?
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You cannot really contrast a person with
rules-known-to-the person
We shall return at intervals to the
Chomsky view that language behaviour
in humans IS rule following (and he can
determine what the rules are!)
Searle says this shows the need
for semantics but semantics
means two things at different
times:
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Access to objects via FORMAL objects
(more symbols) as in logic and the formal
semantics of programs.
Access to objects via physical contact
and manipulation--robot arms or
prostheses (or what children do from a
very early age).
Semantics fun and games
Programs have access only to syntax (says S.).
If he is offered a formal semantics (which is of
one interpretation rather than another) –
that’s just more symbols ( S’s silly reply ).
Soon you’ll encounter the ‘formal semantics of
programs’ so don’t worry about this bit.
If offered access to objects via a robot prothesis
from inside the box: Searle replies that’s just
more program or it won’t have reliable
ostension/reference like us.
Remember Strong AI is the straw man of all
time.
“computers, given the right programs can be
literally said to understand and have other
cognitive states”. (p.417)
Searle has never been able to show that any AI
person has actually claimed this!
[Weak AI – mere heuristic tool for study of the
mind]
Consider the internalised Chinese “speaker”: is
he mentally ill? Would we even consider he
didn’t understand? What semantics might he
lack? For answering questions about S’s
paper? ; for labels, chairs, hamburgers?
The residuum in S’s case is intentional states.
Later moves:
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S makes having the right stuff necessary for
having I-states (becoming a sort of
biological materialist about people;
thinking/intentionality requires our biological
make up i.e. carbon not silicon. Hard to
argue with this but it has no obvious
plausilility).
He makes no program necessary – This is
just circular – and would commit him to
withdrawing intentionality from cats if ….
etc. (Putman’s cats).
The US philosopher Putnam
made it hard to argue that things
must have certain properties.
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He said: suppose it turned out that all
cats were robots from Mars.
What would we do?
Stop calling cats ‘cats’--since they didn’t
have the ‘necessary property’
ANIMATE?
Just carry on and agree that cats
weren’t animate after all?
Dennett: I-state is a term in S’s vocabulary for
which he will allow no consistent set of criteria
– but he wants people/dogs in and machines
out at all costs.
Suppose an English speaker learned up
Chinese by tables and could give a good
performance in it? (And would be like the
operator OUT OF THE ROOM)
Would Searle have to say he had no I-state
about things he discussed in Chinese?
Is there any solution to the issues raised
by Searle’s Chinese Room? Are there
any ways of giving the symbols real
meaning?
Symbol grounding
Harnad, S. (1990) The Symbol
Grounding Problem. Physical D 42,
335-346.
Copy of paper can be obtained from:
(http://www.cogsci.soton.ac.uk/harnad/genpub.html)
computation consists of manipulation of
meaningless symbols.
For them to have meaning they must be
grounded in non-symbolic base.
Like the idea of trying to learn Chinese
from a Chinese dictionary.
Not enough for symbols to be ‘hooked up’
to operations in the real world. (See
Searle’s objection to robot answer.)
Symbols need to have some intrinsic
semantics or real meaning.
For Hanard, symbols are grounded in
iconic representations of the world.
Alternatively, imagine that symbols
emerge as a way of referring to
representations of the world - representations that are built up as a result of
interactions with the world.
For instance, a robot that learns from
scratch how to manipulate and interact
with objects in the world.
(Remember Dreyfus argument that
intelligent things MUST HAVE GROWN
UP AS WE DO)
In both accounts, symbols are no longer
empty and meaningless because they
are grounded in non-symbolic base - i.e.
grounded in meaningful
representations.
(Cf. formal semantics on this view!)
Does Harnard’s account of symbol
grounding really provide an answer to
the issues raised by Searle’s Chinese
Room?
What symbol grounding do humans
have?
Symbols are not inserted into our heads
ready-made.
For example, before a baby learns to
apply the label ‘ball’ to a ball, it will
have had many physical interactions
with it, picking it up, dropping it, rolling
it etc.
Child eventually forms concept of what
‘roundness’ is, but this is based on long
history of many physical interactions
with the object.
Perhaps robotic work in which symbols
emerge from interactions with the real
world might provide a solution.
See work on Adaptive Behaviour e.g.
Rodney Brooks.
Another famous example linking
meaning/knowledge to
understanding:
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This is the argument that we need stored
knowledge to show understanding.
Remember McCarthy’s dismissal of
PARRY--not AI because it did not know
who was US President.
Is knowledge of meaning different from
knowledge of things? ‘The Edelweiss is a
flower that grows in the Alps’.
Famous example from history of
machine translation (MT)
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Bar-Hillel’s proof that MT was
IMPOSSIBLE (not just difficult)
---------------------------------------Little Johnny had lost his box
He was very sad
Then he found it
The box was in the PEN
Johnny was happy again
Bar-Hillel’s argument:
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The words are not difficult nor is the
structure
To get the translation right in a language
where pen is NOT both playpen and
writing pen,
You need to know about the relative
sizes of playpens, boxes and writing
pens.
I.e you need a lot of world knowledge
One definition of AI is:
knowledge based processing
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Bar-Hillel and those who believe that in
AI, look at the ‘box’ example and
AGREE about the problem (needs
knowledge for its solution)
DISAGREE about what to do (for AI it’s
a task, for B-H impossible)
Does the web change this question at
all?
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