Cognitive Science

Introduction to Cognitive Science Sept 2006 :: Lecture #1 :: Joe Lau :: Philosophy HKU

Please write this down http://philosophy.hku.hk/courses/200607/cogn1001

Topics   

About this course What is cognitive science? The computer model of the mind

About this course

About this course    

Course coordinator Other teachers Course tutor Assessment  60% 2-hour final exam.  25% 5 problem sets; one for each topic.  10% tutorial participation.  5% tutorial attendance.

What is cognitive science?

Longuet-Higgins, H.C. (1973) Comments on the Lighthill report. Artificial Intelligence - A Paper Symposium. London: Science Research Council. By 1960 it was clear that something interdisciplinary was happening. At Harvard we called it cognitive studies, at CarnegieMellon they called in information-processing psychology, and at La Jolla they called it cognitive science. – George Miller.

What is cognitive science? Cognitive science is the science of mind and behavior. How is it different from psychology?

“Cognitive” 



Of or pertaining to cognition, or to the action or process of knowing (OED) Understanding knowledge acquisition and use is the key to understanding the mind.

Colorless green ideas sleep furiously.

So what is cognitive science? 

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Cognitive science is a scientific study of the mind with special emphasis on the use and acquisition of knowledge and information. Implications 

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An inter-disciplinary approach – Many scientific disciplines contribute to cognitive science. A computational approach – Explain information processing in terms of neural computations.

Information processing everywhere 

Perception 

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Language use 

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combining different sources of information, deriving new information, testing consistency of information, etc.

Action 

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making use of information about syntax, semantics and phonology.

Reasoning 

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acquiring real-time information about the surrounding environment.

making use of information in action planning and guidance.

Memory 

storing and retrieving information

This is one reason why cognitive science is inter-disciplinary.

Explaining information processing  

What is the best explanation of why a system is capable of complex information processing? Answer: The system is a computer.

Why there was no cognitive science 

They didn’t think that knowledge is the key.  



Perhaps it is a special substance? (Dualism) Perhaps it is stimulus-response? (Behaviorism)

They didn’t know about computers. 

Small stupid steps combine to do difficult things.

A useful short history: http://ls.berkeley.edu/ugis/cogsci/major/about.php

VIP #1 Cognitive science is about how the mind processes information.

What is special about cognitive science? 

Focuses on knowledge and information as the key to understanding the mind.     

Interdisciplinary Computational approach Special relevance to IT and AI Individualistic Multi-level explanations

Psychology

Social psychology

Educational psychology

Cognitive science

More on the computer model of the mind

Quiz: What is a computer? (a) A person (b) A machine

What is computation? 

Rule-based manipulation of symbols. S = str_replace( “cat” , ”c” , ”h” )

17x11=? Philosophy  哲學 170 17 187

A program is like a cooking recipe Ingredients

recipe

Computational explanation of information processing in the mind 

Thinking that P = activating a set of symbols in the brain which mean P. boring !

Is-in-love Peter Is-happy

Symbols in the mind = mental / neural representation Topographical representation of visual stimulus in visual area V1

Representations explain lots of things 

Example: Syntactic Disambiguation  

“We shall discuss violence on TV.” Two interpretations : VP

VP

V

NP

PP

discuss

N

P

NP

violence on

NP

V

TV

discuss

N

violence P on

PP NP TV

Two methodological consequences of the computer model 

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Computer models can be built to test theories of mental processes. There are different levels of analysis for a complex information processing system.

Three Levels of Description (David Marr)  

A complete understanding of a computational system has to involve three (kinds of) levels : Computational theory  

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Representation and algorithm (software)  

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What is computed and why. What the system is capable of doing.

What program is used. What are the symbols and how are they processed.

Hardware  

Where in the brain? What kind of neurons and how are they connected?

Example 

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Task: Multiplication. Input numbers x and y. Output x times y. Algorithm: Given inputs x and y, look up number z on row x and column y. Output z. Implementation: human being and paper.

Alternative algorithm 

How to calculate x times y:  



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If x =1, then answer is y. If x>1, add y to itself (x-1) number of times. The result is the answer. Example: 3x5 = 5+5+5 = 15

Implementation:

Two points 

The same task can be performed with different algorithms. 



Two different systems can do the same task in very different ways.

The same algorithm can be implemented with different hardware.

How to study cognitive science A

computational theory of X should explain X at three levels. What is computed? Visual motion  How? Correlate changes in luminance at different places.  Hardware? Comparator circuits 

http://www.psypress.co.uk/mather/resources/swf/Demo11_1.swf

Demo http://www.psypress.co.uk/mather/resources/swf/Demo11_1.swf

Application: linguistic understanding 

Task 

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Algorithm 

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Identify syntax and meaning corresponding to speech sounds. What kind of computation and mental representations?

Implementation 

Which part of the brain?

VP V discuss

NP

PP

N

P

NP

on

TV

violence

INTERDISCIPLINARY approach 

Division of labour 

   

Psychology – cognitive psychology, developmental psychology … Linguistics – syntax, semantics, phonology … Neuroscience – brain structures, localization … Computer science – AI, computer models … Philosophy – theoretical foundations …

How to think about cognitive science Language Task Algorithm Hardware

Vision

Reasoning

Other areas

If you get lost  Which 

Language, reasoning, emotions, …

 Which 

mental process? level?

Task, algorithm, neural implementation

Summary 

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Cognitive science is an inter-disciplinary science of mind and behavior. The computational approach : using computations and representations to explain mental processes. Three levels of descriptions. Coming up next: language as an example.