introduction to cognitive science sept 2005 :: lecture #1 :: joe lau :: philosophy hku
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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?