Introduction to Cognitive Science

Sept 2005 :: Lecture #1 :: Joe Lau :: Philosophy HKU

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

About this course

About this course Course coordinator

Joe Lau Other teachers Course tutors

Antonio Cheung and Elaine Lau Course web site

http://philosophy.hku.hk/courses/cogn1001 Assessment

60% exam -- 2 hours. 25% problem sets -- 5 problem sets; one for each topic. 10% tutorial participation. 5% tutorial attendance.

What is cognitive science?

What is cognitive science? Answer : Cognitive science is the

science of mind and behavior.

Feature #1 Cognitive science studies MIND AND BEHAVIOR Mental states and processes inside the brain

Emotions, knowledge of language, reasoning … The behavior caused by these processes

Facial expressions, speech … The normal mind The abnormal mind

Autism, Cotard delusion …

Feature #2 Cognitive science is a SCIENCE.

Theories and hypotheses have to be tested. How? Check whether they can explain the

data from experiments and observations.

Why study cognitive science?

Intellectual value Practical value

Education AI and technology Medical application

Educational value Entertainment value!

“ Man is the Measure of all Things. ”Protagoras of Abdera

( c. 480-410 B.C.)The Mind

Methodology of cognitive science

Methodology Some distinctive features about research m

ethods and explanations in cogsci. Brain-based explanations Functional explanations Interdisciplinary approach The computational model of the mind

400 BC - Hippocrates Founder of Western medicine “Men ought to know that from the

brain, and from the brain only, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, grievances, and tears. Through it...we...think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant.”

Brain-based explanations The mind is explained in terms of physical

processes in the brain. (pace Aristotle)

What about Dualism? Dualism - The mind is a soul. Not to be decided a priori. Need experiments. BBE is the default hypothesis because it has

been more successful and has better predictive power.

However, the brain is a very, very, very complex system. (100 billion neurons vs. 6 billion

people)

Some of the connections between the different visual systems.

How to deal with this complex system?

1. Functional approach Understand the functions of different systems of

the brain and see how they interact. Visual areas, language, emotions …

Cognitive science is like reverse engineering.

2. Inter-disciplinary approach

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 …

The computer model of the mind The mind is like a computer. A distinctive feature of cognitive science.

What is the computer model? The mind is an information processing syste

m. Information processing is best explained by

computations and symbols. Information processing in the computer = progra

ms operating on symbols. Information processing in the brain = neural comp

utations involving mental representations.

A typical computer Inside a computer, we have :

Symbolse.g. HTML color codes

symbols are objects to which meaning can be assigned.

Programse.g. Str_replace( “I have a cat” , ”c” , ”h” )

programs are procedures for manipulating symbols.

Boring!

Mental representations Mental representations

are symbols in the brain that have meaning or encode information.

Thinking P ~ Activating a mental representation that means P.

Is-in-love

Thinking as neural computation

Peter

Is-happy

Is-in-love

Is-happy

Why should we accept the computational model

of the mind?

Some reasons Information processing does seem to be a

distinctive feature of the mind. Mental representations are useful in

explaining lots of mental phenomena. We can observe mental representations.

Information processing in the mind Perception

acquiring real-time information about the surrounding environment.

Language use making use of information about syntax, semantics and

phonology. Reasoning

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

Action making use of information in action planning and guidance.

Memory storing and retrieving information

They help us explain lots of things Example: Syntactic Disambiguation

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

VP

V

NP

NP PP

Ndiscuss

violence

on TV

P

VP

V NP

Ndiscuss

violence NP

PP

on TV

P

A real representation

Topographical representation of visual stimulus in area V1

Two methodological consequences of the computer model

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 : Task : what the system is capable of doing

(capacities) Algorithm (software) : which computational

procedures are used Implementation (hardware) : how the

computations are implemented

Example

Task: Multiplication Algorithm: input

numbers x and y. Output number in row x and column y.

Implementation: human being and paper.

1 2 3 4 5

2 4 6 8 10

3 6 9 12 15

4 8 12 16 20

5 10 15 20 25

Different algorithmsSame task

Task : calculate X2-1 Algorithm #1 : X2-1 = (X+1)•(X-1)

52-1 = (5+1)(5-1) = 6·4 = 24 Algorithm #2 : X2-1 = X•X-1

52-1 = (5·5)-1=25-1=24

Same taskDifferent hardware implementations

Exercise: Can you give an example where the same algorithm is implemented in different hardware?

1 2 3 4 5

2 4 6 8 10

3 6 9 12 15

4 8 12 16 20

5 10 15 20 25

Application: linguistic understanding

Task Identify grammatical structure and meaning

of speech sounds.

Algorithm What kind of computation and

mental representations?

Implementation Which part of the brain?

VP

V

NP

NP PP

Ndiscuss

violence

on TV

P

How to think about cognitive science

Language Vision ReasoningOther areas

Task

Algorithm

Hardware

If you get lost Which mental process?

Language, reasoning, emotions, …

Which level? Task, algorithm, neural implementation

Summary Cognitive science as an inter-disciplinary

science of mind and behavior. The computational approach : using

computations and representations to explain mental processes.

Three levels of descriptions.

Finally, to end …

Scope of the computer model? Computations are NECESSARY for underst

anding the mind because the mind processes information.

Are computations SUFFICIENT for understanding everything about the mind?

What about consciousness?