1. COGN1001 Introduction to Cognitive Science Sept 2006 :: Lecture #1 :: Joe Lau :: Philosophy HKU

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

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

4. About this course

5. 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.

6. 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 Carnegie- Mellon they called in information-processing psychology, and at La Jolla they called it cognitive science. – George Miller.

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

8. “ 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.

9. So what is cognitive science? Cognitive science is a scientific study of the mind with special emphasis on the use and acquisition of knowledge and information. Implications An inter-disciplinary approach – Many scientific disciplines contribute to cognitive science. A computational approach – Explain information processing in terms of neural computations.

10. Information processing everywhere 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 This is one reason why cognitive science is inter-disciplinary.

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

12. 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

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

14. 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

15. Social psychology Educational psychology Psychology Cognitive science

16. More on the computer model of the mind

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

18. What is computation? Rule-based manipulation of symbols. 17x11=? 170 17 187 S = str_replace( “cat”, ”c”, ”h” ) Philosophy  哲學

19. A program is like a cooking recipe recipe Ingredients

20. 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 Is-in-love Is-happy

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

22. Representations 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

23. 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.

24. Three Levels of Description (David Marr) A complete understanding of a computational system has to involve three (kinds of) levels : Computational theory What is computed and why. What the system is capable of doing. Representation and algorithm (software) 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?

25. Example 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.

26. Alternative algorithm How to calculate x times y: 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:

27. 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.

28. 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

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

30. Application: linguistic understanding Task Identify syntax and meaning corresponding to 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

31. 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 …

32. How to think about cognitive science LanguageVisionReasoning Other areas Task Algorithm Hardware

33. If you get lost Which mental process? Language, reasoning, emotions, … Which level? Task, algorithm, neural implementation

34. Summary 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.