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

Course coordinator Joe Lau Other teachers Course tutors Antonio Cheung and Elaine Lau Course web site 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?

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 B.C.) The Mind

Methodology of cognitive science

Methodology Some distinctive features about research methods 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 system. Information processing is best explained by computations and symbols. Information processing in the computer = programs operating on symbols. Information processing in the brain = neural computations involving mental representations.

A typical computer Inside a computer, we have : Symbols e.g. HTML color codes symbols are objects to which meaning can be assigned. Programs e.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 PP Ndiscuss violence on TV P VP V NP Ndiscuss violenceNP 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

Different algorithms Same task Task : calculate X 2 -1 Algorithm #1 : X 2 -1 = (X+1) (X-1) = (5+1)(5-1) = 6·4 = 24 Algorithm #2 : X 2 -1 = X X = (5·5)-1=25-1=24

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

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 PP Ndiscuss violence on TV P

How to think about cognitive science LanguageVisionReasoning Other 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 understanding the mind because the mind processes information. Are computations SUFFICIENT for understanding everything about the mind? What about consciousness?