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Cognitive Psychology

Part I:

Where does Cognitive Psychology fit within Cognitive Science?

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Just about everywhere.

Almost all research in Cognitive Science is relevant to some

Cognitive Psychologist.

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Important Concepts

• Three levels of organization of intelligent systems (Pylyshyn, 1999)– Physical/Biological– Syntactic/Symbolic– Semantic/Knowledge

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• Three levels of understanding information processing (Marr, 1982)– Hardware Implementation– Representational Algorithm– Computational Theory

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Computational Theory(knowledge/semantics)

• What is the goal of the computation?

See a brown dog

Pet the brown dog

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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?

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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.

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• 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

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What’s not Cognitive Psychology?

• Purely “engineering” solutions (e.g. Deep Blue II)– Building jet airplanes doesn’t help us better

understand birds

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Reading AssignmentWeek 2

• Pylyshyn, Z. (1999). What’s in your mind? In Lepore, E. & Pylyshyn, Z. (Eds.) What is Cognitive Science (pp. 1-25). Oxford, Blackwell.

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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).

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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.

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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)

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Part II

What is Cognitive Psychology?

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Cognitive Psychology

How• Experimental• Biological• Computational

What• Perception• Categorization• Representation• Memory• Attention• Learning• Thought

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Why do experiments?

“Human beings were not created for the convenience of

experimental psychologists.” George Miller (in Barsalou, 1992)

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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)

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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.

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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.

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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

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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?

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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

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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

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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?

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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, 3-71.• Goldstone, R. L., & Barsalou, L. W. (1998). Reuniting perception and conception. Cognition, 65, 231-262. • 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, 527-542.• 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. 104-106). 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, 81-97.• 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, 701-703.• Stroop, J. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18,

624-643.• Wu, L., (1995). Perceptual Representation in Conceptual Combination. Doctoral dissertation, University of

Chicago