Transcript Introduction to Cognitive Science

COGN1001
Introduction to
Cognitive Science
Sept 2006 :: Lecture #1 :: Joe Lau :: Philosophy HKU
Please write this down
http://philosophy.hku.hk/courses/200607/cogn1001
Topics
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About this course
What is cognitive science?
The computer model of the mind
About this course
About this course
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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”
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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
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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
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storing and retrieving information
This is one reason why cognitive science is inter-disciplinary.
Explaining information processing
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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
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They didn’t think that knowledge is the key.
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Perhaps it is a special substance? (Dualism)
Perhaps it is stimulus-response? (Behaviorism)
They didn’t know about computers.
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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?
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Focuses on knowledge and information as
the key to understanding the mind.
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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?
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Rule-based manipulation of symbols.
S = str_replace( “cat” , ”c” , ”h” )
17x11=?
170
17
187
Philosophy  哲學
A program is like
a cooking recipe
Ingredients
recipe
Computational explanation of
information processing in the mind
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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
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Example: Syntactic Disambiguation
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“We shall discuss violence on TV.”
Two interpretations :
VP
VP
V
NP
PP
discuss
N
P
NP
V
NP
discuss
N
PP
violence P
violence
on
TV
on
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)
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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
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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
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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
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The same task can be performed with
different algorithms.
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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
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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
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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
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Which part of the brain?
VP
V
discuss
NP
PP
N
P
NP
on
TV
violence
INTERDISCIPLINARY approach
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Division of labour
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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
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Language, reasoning, emotions, …
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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.