1 19 September, 2000HKU Cognitive Psychology Part I: Where does Cognitive Psychology fit within Cognitive Science?

2 19 September, 2000HKU Just about everywhere. Almost all research in Cognitive Science is relevant to some Cognitive Psychologist.

3 19 September, 2000HKU Important Concepts Three levels of organization of intelligent systems (Pylyshyn, 1999) –Physical/Biological –Syntactic/Symbolic –Semantic/Knowledge

4 19 September, 2000HKU Three levels of understanding information processing (Marr, 1982) –Hardware Implementation –Representational Algorithm –Computational Theory

5 19 September, 2000HKU Computational Theory (knowledge/semantics) What is the goal of the computation? See a brown dog Pet the brown dog

6 19 September, 2000HKU Representation & Algorithm (Syntactic/Symbolic) How to implement these goals? How are the inputs and outputs represented? –What must be done to “see” a brown dog? –To “pet” the brown dog? What is the algorithm for transforming one to the other?

7 19 September, 2000HKU Hardware Implementation (biological/physical) What physical equipment is needed to implement these representations and algorithms? Retina(s) Interneurons Motoneurons Muscles Arm/hand Proprioceptors Tactile sensory neurons Etc.

8 19 September, 2000HKU The three levels (theory, representation & algorithm, and implementation) are useful organizing principles in all of Cognitive Science Psychology is mostly concerned with the second level: Representation and Processing

9 19 September, 2000HKU What’s not Cognitive Psychology? Purely “engineering” solutions (e.g. Deep Blue II) –Building jet airplanes doesn’t help us better understand birds

10 19 September, 2000HKU Reading Assignment Week 2 Pylyshyn, Z. (1999). What’s in your mind? In Lepore, E. & Pylyshyn, Z. (Eds.) What is Cognitive Science (pp. 1-25). Oxford, Blackwell.

11 19 September, 2000HKU Warning Pylyshyn is very biased (but not necessarily wrong). Opposed to behaviorism (1.1–1.2, 4.1). Opposed to connectionism (In favor of symbolic representations) (4.2).

12 19 September, 2000HKU Behaviorism We can only understand an organism’s behavior by studying physical stimuli and how the organism reacts to them. It is not possible to observe the internal workings of the mind, so don’t propose internal constructs (goals/desires, mental representations, algorithms, etc.) Now largely abandoned. In Cognitive Psychology it is now common and accepted to postulate internal constructs.

13 19 September, 2000HKU Connectionism Computational models of behavior. Modeled on the brain (neural networks). Do not rely on symbolic expressions. Can perform a surprising range of computational/behavioral tasks. Can’t do everything humans can? (Fodor & Pylyshyn, 1988)

14 19 September, 2000HKU Part II What is Cognitive Psychology?

15 19 September, 2000HKU Cognitive Psychology How Experimental Biological Computational What Perception Categorization Representation Memory Attention Learning Thought

16 19 September, 2000HKU Why do experiments? “Human beings were not created for the convenience of experimental psychologists.” George Miller (in Barsalou, 1992)

17 19 September, 2000HKU Control the situation Most phenomena could have many causes, how do we know which one is the (main) cause? Test each possibility, one by one. Need to eliminate chance of other causes taking effect (control)

18 19 September, 2000HKU Some ways to control variables Select your subjects carefully –Only right-handed, male, native English speakers Create your stimuli carefully –Record specific syllables spoken by a trained talker Choose a simple environment –Empty room, sound booth, etc.

19 19 September, 2000HKU Manipulate your subjects Experiments crucially involve a comparison of (at least) two groups (who may still be the same people). The difference between the groups is caused by manipulation of experimental variables.

20 19 September, 2000HKU Some Experimental Manipulations Between group comparisons: –2 year-old children vs. 6 yr olds –English speakers vs. Cantonese speakers –University students vs. early school leavers Within group comparisons: –Untrained listeners vs. trained listeners –Listening to Cantonese vs. listening to English –Dosed with a drug vs. with a placebo

21 19 September, 2000HKU For example Question: Does knowing how to speak one tone language make it easier to hear the tones of a different tone language? (easier than it is without knowing a tone language) Possible answers: –Yes, perception of tone is universal – if you’ve got it, you’ve got it. –No, perception of tone is language-specific. You must learn the sound system of each language separately. How do we test this?

22 19 September, 2000HKU Lee, Vakoch, & Wurm (1996) Three groups: Cantonese, Mandarin, and English speakers Two sets of sounds: Cantonese and Mandarin (presented in pairs, grouped by language) Asked subjects “same or different” for each pair

23 19 September, 2000HKU Lee, Vakoch, & Wurm (1996) Cantonese tones: Cantonese > Mandarin = English Mandarin tones: Mandarin > Cantonese > English Conclusions: –Native language is best –knowing Cantonese helps with Mandarin –Knowing Mandarin does not help with Cantonese

24 19 September, 2000HKU Criticism of experiments Ecologically implausible –“same-different” task is unlike real speech perception Small answers to small problems –What do we really know now that we didn’t know before?

25 19 September, 2000HKU Bibliography Barsalou, L. W. Cognitive Psychology: An Overview for Cognitive Scientists. Hillsdale, NJ, Lawrence Erlbaum and Associates. Coren, S. & Ward, L. M. (1989). Sensation and Perception, Third Edition. Fort Worth, NJ, Harcourt Brace Jovanovich. Fodor, J. A. & Pylyshyn, Z. W. (1988). Connectionism and cognitive architecture: a critical analysis. Cognition, 28, Goldstone, R. L., & Barsalou, L. W. (1998). Reuniting perception and conception. Cognition, 65, Lee, Y.-S., Vakoch, D. A., & Wurm, L. H. (1996). Tone perception in Cantonese and Mandarin: A cross- linguistic comparison. Journal of Psycholinguistic Research, 25, Marr, D. (1982). Vision. New York, W. H. Freeman & Company. Medin, D. L. & Aguilar, C. (1999). Categorization. In Wilson, R. A. & Keil, F. C. (Eds.) The MIT Encyclopedia of the Cognitive Sciences (pp ). Robert A. Wilson and Frank C. Keil. Cambridge, MA, MIT Press. Miller, G. A. (1956). The magical number seven plus or minus two: Some limits on our capacity for processing information. Psychological Review, 63, Pylyshyn, Z. W. (1999). What’s in your mind? In Lepore, E. & Pylyshyn, Z. W. (Eds.) What is Cognitive Science (pp. 1-25). Oxford, Blackwell. Shepard, R. N., & Metzler, J. Mental rotation of three-dimensional objects. Science, 171, Stroop, J. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, Wu, L., (1995). Perceptual Representation in Conceptual Combination. Doctoral dissertation, University of Chicago