4 questions (Revisited)
What are our underlying assumptions about
intelligence?
 What kinds of techniques will be useful for
solving AI problems?
 At what level of detail are we trying to model
human intelligence?
 How will we know when we have succeeded
in building an intelligent program?

1
Symbolic vs. Subsymbolic AI
Subsymbolic AI: Model intelligence
at a level similar to the neuron. Let
such things as knowledge and
planning emerge.
Symbolic AI: Model such things
as knowledge and planning in
data structures that make sense to
the programmers that build them.
(blueberry (isa fruit)
(shape round)
(color purple)
(size .4 inch))
2
Interest in Subsymbolic AI
40
50
60
70
80
90
00
10
3
Low-level (Sensory and Motor) Processing and the
Resurgence of Subsymbolic Systems
•Computer vision
•Motor control
•Subsymbolic systems perform cognitive tasks
•Detect credit card fraud
•The backpropagation algorithm eliminated a formal weakness of
earlier systems
•Neural networks learn.
4
Turing test
AI system
Experimenter
Control
5
Eliza, 1965

HUMAN: You are like my father in some ways.
ELIZA: What resemblance do you see?
HUMAN: You are not very aggressive, but I think you don’t want me to notice that.
ELIZA: What makes you think I am not very aggressive?
HUMAN: You don’t argue with me.
ELIZA: Why do you think I don’t argue with you?
HUMAN: You are afraid of me.
ELIZA: Does it please you to believe I am afraid of you?
HUMAN: My father is afraid of everybody.
ELIZA: What else comes to mind when you think of your father?
HUMAN: Bullies.
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http://www-ai.ijs.si/eliza/
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6
The Chinese Room
She does
not know
Chinese
Correct
Responses
Chinese
Writing is
given to the
person
Set of rules, in
English, for
transforming
phrases
7
The Chinese Room Scenario
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An individual is locked in a room and given a batch of Chinese writing. The
person locked in the room does not understand Chinese.
Next she is given more Chinese writing and a set of rules (in English which
she understands) on how to collate the first set of Chinese characters with
the second set of Chinese characters.
If the person becomes good at manipulating the Chinese symbols and the
rules are good enough, then to someone outside the room it appears that
the person understands Chinese.
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The Chinese Room (cont.)
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Searle's, who developed the argument, point is that she doesn't really
understand Chinese, she really only follows a set of rules.
Following this argument, a computer could never be truly intelligent, it is only
manipulates symbols. The computer does not understand the semantic context.
Searle’s criteria is “intentionality,” the entity must be intentionally exhibiting the
behavior, not simply following a set of rules.
Intentionality is as difficult to define as intelligence.
Searle excludes ‘weak AI’ from his argument against the possibility of AI.
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Philosophical extremes in AI
Weak AI vs. Strong AI

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Weak AI believes that machine intelligence need only mimic the behavior of
human intelligence
Strong AI demands that machine intelligence must mimic the internal processes of
human intelligence, not just the external behavior
10
Newell and Simon Prediction
In 1997, Deep Blue beat Gary
Kasparov.
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Why Did They Get it Wrong?
They failed to understand at least three key things:
•The need for knowledge (lots of it)
•Scalability and the problem of complexity and exponential
growth
•The need to perceive the world
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Scalability
Solving hard problems
requires search in a large
space.
To play master-level chess
requires searching about 8
ply deep. So about 358
nodes must be examined.
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Exponential Growth
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But Chess is Easy
•The rules are simple enough to fit on one page
•The branching factor is only 35.
15
A Harder One
John saw a boy and a girl with a red wagon with one blue and one
white wheel dragging on the ground under a tree with huge branches.
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How Bad is the Ambiguity?
•Kim (1)
•Kim and Sue (1)
•Kim and Sue or Lee (2)
•Kim and Sue or Lee and Ann (5)
•Kim and Sue or Lee and Ann or Jon (14)
•Kim and Sue or Lee and Ann or Jon and Joe (42)
•Kim and Sue or Lee and Ann or Jon and Joe or Zak (132)
•Kim and Sue or Lee and Ann or Jon and Joe or Zak and Mel (469)
•Kim and Sue or Lee and Ann or Jon and Joe or Zak and Mel or Guy (1430)
•Kim and Sue or Lee and Ann or Jon and Joe or Zak and Mel or Guy and Jan (4862)
 2n   2n 

Cat (n)     
 n   n  1
17
The Differences Between Us and Them
Emotions
Understanding
Consciousness
18
Today: Computer as Artist
Two paintings done by Harold Cohen’s Aaron program:
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Solving AI Problems

Define and analyse the problem
– What knowledge is necessary?

Choose a problem-solving technique

e.g. Chess
– What information do we need to represent in a
chess-playing program?
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‘State Space’
r k b ki q b k r
Initial state
p p p p p p p p

operators
P P P P P P P P
R K B KI Q B K R
p p
k
Goal state(s)
q
KI
21
The Water Jugs Problem
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2 jugs
– 4 gallon
– 3 gallon
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3
4
How can you get exactly 2 gallons into the 4 gallon
jug?
Possible operators:
1. Empty jug
2. Fill jug from tap
3. Pour contents from one jug into another
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