Download Lecture 28: Physical symbol system

Course Seminar - CS 344
Physical Symbol System
Hypothesis
Gagan Deep Kaur
Roll No. 07408802
Physical Symbol System
A PSS consists of
- Symbols - set of entities that are physical patterns
- Symbol Structures - number of instances/tokens related in
some physical way
- Processes – operate on these expressions to produce other
expressions
S1
Symbol
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S1
S2
S3
S4
S5
S6
Symbol
Structures “Expressions”
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
S13
S14
S15
S16
S17
S18
S19
S20
S21
S22
S23
S24
S25
S26
S27
S28
S29
S30
At any given time, a PSS contains
- collection of expressions
- processes to operate on these expressions
creation, modification, reproduction, destruction
Collection of
“Expressions”
Physical Symbol System
Key Concepts
Designation – the symbol/expressions can refer to something
else.
Interpretation – the expressions can refer to its own
computational processes which the system can evoke and
execute
Examples of Symbol Systems
System
Symbol
Expressions
Processes
Logic
And, Or, Not,
Propositions (T/F)
Rules of Inference
Algebra
+, -, *, /,
y, z, 1, 2, 3….
Equations
(2+3=5)
Rules of Algebra
Digital Computer
0, 1
00000111000…..
Program
-----Chess
Chess Pieces
Position of pieces
on the board
Legal Chess
Moves
Physical Symbol System Hypothesis
- By Allen Newell and Herbert Simon
“A physical symbol system has the necessary
and sufficient means for general intelligent action”
Claims
- Human thinking is a kind of symbol manipulation
- Symbol manipulation necessary for intelligence
- Machines can be intelligent, because
- Symbol manipulation is sufficient for intelligence
Core assumption of Strong AI
Grounds of PSS
Brain similar with a physical symbol system
Psychological Experiments – decision making, learning processes
Running AI programs –chess, checkers, theorem proving,
Clark – Productivity of Human Thoughts
Examples of PSS
System
Symbol
Expressions
Processes
Digital Computer
0, 1
00000111000…..
Program
-----Chess
Chess Pieces
Position of pieces
on the board
Legal Chess
Moves
Brain
Encoded in brain
Thoughts
Mental Operations
like thinking
AI Program
Data
Data
Data
Merits
Computationally possible to encode symbolic human
knowledge
Opened avenue for machine intelligence!
Implications
Appropriately programmed computer is capable of conscious
thought
Machines can
understanding
be
made
to
think
and
have
Can Physical Symbol Systems Think?
genuine
symbol manipulation = intelligence?
Critiques
Serial manipulation of
discrete symbols
(PSS)
≠
parallel and distributed
processing
(Human Brain)
Dreyfus – Role of unconscious instincts than conscious symbol
manipulation
Searle’s Chinese Room
Searle’s Chinese Room
Searle’s Chinese Room
Intelligence requires Understanding.
Does the program understands the symbols that it uses?
Does “symbols” have any meaning for the machine?
Conclusion
The question thus boiled down to this:
Could a system think or understand just by having right sort
of program?
Is syntax enough to ensure “semantics” which is necessary
for understanding.
Can Physical Symbol System be
Intelligent?
References
Clark, Andy, “Philosophical Implications”, Artificial Intelligence, Ed. Margaret
Boden, Academic Press, California, 1996
Dreyfus, Hubert, What Computers Can’t Do: The Limits of AI, Harper & Row,
New York, 1979
Newell, Allen and Simon, Herbert, “Computer Science and Empirical Inquiry:
Search and Symbols”, Mind Design II, Ed. John Hagueland, MIT Press, 1997,
Searle, John, “Minds, Brains and Programs”, Minds I, Ed. Douglas Hofstadter,
and Daniel Dennett, Basic Books, 2001, P. 282-306
Wikipedia, Stanford Encyclopedia
Various Internet Sources For The Pictures!