Introduction to Cognitive Science

Philosophy

Nov 2005 :: Lecture #2 :: Joe Lau :: Philosophy HKU

Last week The role of philosophy in cognitive science A brief history of cognitive science Philosophical theories of the mind

Today The computer model of the mind Challenges to the computer model

The computer model of the mind

Weak version - Computations are necessary for explaining mental processes. The mind has a computational level of

description.

Strong version - Computations are necessary and sufficient for explaining mental processes.

Implications of the strong version

The right kind of computation will be sufficient for the existence of a mind.

For all / some mental states?

Alan Turing’s 1950 paper Alan Turing (1950). Computing Machinery and

Intelligence. Mind 49: 433-460. Introduced computers to philosophy. Argued for the plausibility of thinking machines. Proposed the “Turing test” for intelligence.

Alan Turing (1912-1954)http://www.turing.org.uk/turing/

Famous British mathematician / logician Mathematical theory of computation. Practical design of electrical computers.

Helped cracked the German U-boat Enigma code in WWII.

A homosexual, arrested in 1952. Committed suicide.

Objection: Computers cannot think The theological objection “Heads in the sand” objection The mathematical objection The argument from consciousness Arguments from various disabilities Lady Lovelace’s objection Argument from continuity Argument from informality The ESP argument

The theological objection “Thinking is a function of man's immortal soul. God

has given an immortal soul to every man and woman, but not to any other animal or to machines. Hence no animal or machine can think.”

Turing Animals can also think. Do not underestimate God’s ability. Theological arguments are unreliable.

The “Heads in the sand” objection

“The consequences of machines thinking would be too dreadful. Let us hope and believe that they cannot do so.”

Computers cannot make mistakes

Turing: Why is this an objection to the possibility of a thinking machine?

Turing: Errors of functioning vs. conclusion. Statistical reasoning, heuristic reasoning can

lead to false conclusions. All the swans I have seen are white.

So all swans are white. If an email contains “sex”,

it is a spam email.

Lady Lovelace’s objection

Ada Bryon 1815-52 Daughter of poet Byron Promoted Babbage’s machi

nes Predicted that machines can

write music and assist research

First programmer? (Probably not)

An often-quoted comment “The Analytical Engine has no pretensions

whatever to originate anything. It can do whatever we know how to order it to perform. It can follow analysis; but it has no power of anticipating any analytical relations or truths. Its province is to assist us in making available what we are already acquainted with.”

Computers cannot be creative

Is creativity necessary for thinking? “It can do whatever we know how to order it

to perform.” Is determinism the problem?

Determinism – A deterministic system is a system whose behavior is fixed by its initial state and the laws of physics.

How do we know that determinism is not true of us?

What if a computer includes some random element?

Determinism and creativity Why is determinism incompatible with creati

vity? “Creativity requires breaking rules. Comput

ers always follow rules.” Distinguish between programming rules an

d conventional rules.

Computation and creativity

“It can follow analysis; but it has no power of anticipating any analytical relations or truths.”

How can computation produce new ideas? Random element Rearrange old ideas Learning Search, and other methods

Look-ahead tree

But will the computer be sad if it loses? The problem of emotions.

Can machines have emotions? No machine can “be angry or depressed

when it cannot get what it wants.”

But are emotions necessary for thinking?

Three dimensions of emotions Behavior associated with emotions

Facial expressions Other actions

Cognitive states Anger: Believing that someone has been wronged. Jealousy: Wanting what the another person has.

Subjective feelings Valence - Pleasure, displeasure Bodily feelings - Racing heartbeat …

Emotional behavior Facial expressions

http://www.takanishi.mech.waseda.ac.jp/research/eyes/we-4/

Behavior not difficult Aggression Withdrawal

But do they correspondto real emotions?

Cognitive states in emotions Beliefs and desires

Anger: Believing that someone has been wronged. Jealousy: Wanting what the another person has.

Computational explanations of: Belief system

Big database + reasoning mechanism.

Desires A value system: degrees of desires. Assigning value ratings to possible situations. Linked to action.

The problem of consciousness Phenomenal consciousness =

Subjective feelings Qualitative properties of experiences Qualia

Can computations explain qualia? A bad argument

“A computer can never be conscious because we can never know or prove that it is.”

The problem of consciousness Leibniz’s mill argument (1646-1716)

And supposing there were a machine, so constructed as to think, feel, and have perception, it might be conceived as increased in size, while keeping the same proportions, so that one might go into it as into a mill. That being so, we should, on examining its interior, find only parts which work one upon another, and never anything by which to explain a perception. Thus it is in a simple substance, and not in a compound or in a machine, that perception must be sought for.

Is this a good argument?

Objection to the argument Fallacy of composition

Every part of X lacks property P. So X lacks property P.

Example Every part of the car is inexpensive. So the whole car is inexpensive.

But consciousness might be an emergent property of the whole system.

The fading qualia argument See section 3 of Chalmers (1995). Absent Qualia, Fading Qualia, Dancing Qualia.

In Thomas Metzinger (ed.) Conscious Experience. Imprint Academic. http://consc.net/papers/qualia.html

Thought experiment Imagine that you are looking at a red wall, while yo

ur brain cells are replaced by functionally equivalent nano-computers one by one.

What would happen to your qualia? Fading gradually Disappearing suddenly No change

Implications of the argument

Qualia determined by functional organization.

Neurophysiological properties not directly relevant to consciousness.

Qualia can occur in non-biological systems.

Strength of the argument Not a conclusive proof.

Maybe functional equivalence is impossible through replacement.

Maybe qualia will change.

A plausibility argument Default position pending additional consideration

s.

Other issues Discussed intentional states and qualia. How about

The self Freewill Any other mental phenomena?