Physical Symbol System Hypothesis

Gagan Deep KaurRoll No. 07408802

Course Seminar - CS 344

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

S6 S5 S4 S3S2 S1

Symbol

SymbolStructures - “Expressions”

S1

CC$7899ABVV

S6 S5 S4 S3S2 S1

Collection of “Expressions”

S12 S11

S10 S9S8 S7

S18S17S16S15S14S13

S24S23S22S21S20S19

S30S29S28S27S26S25

At any given time, a PSS contains- collection of expressions- processes to operate on these expressions creation, modification, reproduction, destruction

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 be made to think and have genuine understanding

Can Physical Symbol Systems Think?

symbol manipulation = intelligence?

Critiques

Serial manipulation of ≠ parallel and distributeddiscrete symbols processing (PSS) (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 EncyclopediaVarious Internet Sources For The Pictures!