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Categorization

Categorization. Assigning things (percepts, concepts, objects, etc.) to distinct groups in a principled (rule-based) manner. Categorization and Perception. The world is so full of information. How do we know what to look for?. The world is very complex.

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Categorization

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  1. Categorization Assigning things (percepts, concepts, objects, etc.) to distinct groups in a principled (rule-based) manner. HKU

  2. Categorization and Perception HKU

  3. The world is so full of information... How do we know what to look for? HKU

  4. The world is very complex • We cannot process all information available to us – we must selectively attend to what is important to us. • How do we know what to attend to? • We cannot keep track of every individual item in the world – we must group similar things together. • What rules are used to group objects, and how do these rules operate? HKU

  5. What determines what we attend to? • The environment • Some features of the environment give us necessary information. • Our biology • Some aspects of our biology determine what we are capable of attending to. • Experience • It turns out that the problem of having to group things together helps us learn what things in the world to attend to. HKU

  6. The “Horizon ratio”. Most people see the buildings as the same size, and the tower as taller. The ratio above to below the horizon always gives good information about height (except in illusions). Environment HKU

  7. Our Biology • Neural detectors for perceptual properties • Vision: Horizontal lines, vertical lines, dots, directional motion, retinal location (Hubel & Wiesel, 1959, 1962); also color, brightness, simple shapes & solids, etc. • Audition: loudness, pitch, frequency sweeps. • Etc. HKU

  8. Experience • Experience with making categories causes changes in perception. • Acquired equivalence within categories. • Acquired distinctiveness between them. Eleanor Gibson (1969) Robert Goldstone (1998) HKU

  9. Categorical Perception Perceiving a continuous range of stimuli as members of discrete categories. (Harnad, 1987) HKU

  10. Some Physical Continua • Color • Pitch • Loudness • Brightness • Angle • Weight • Etc. HKU

  11. Some physical phenomena are perceived continuously HKU

  12. Some are not HKU

  13. For ExampleA continuum ranging from/da/ to /ga/ (after Delattre, Liberman, & Cooper, 1955) Good /da/ Good /ga/ 1 2 3 4 5 6 7 8 HKU

  14. Identification:Discontinuity at Boundary HKU

  15. Pairwise Discrimination:Same or Different? HKU

  16. Pairwise Discrimination(same/different) HKU

  17. What Happened? 1 2 3 4 5 6 7 8 Physical World Perceptual Representation 1 2 3 4 5 6 7 8 HKU

  18. Categorical Perception Identification determinesDiscrimination HKU

  19. Traditional view of CP • Discrimination is only possible (above chance) across a category boundary. • Within a category, all tokens are perceived as identical. HKU

  20. Another Example Level Tone Continuum Tone 6 Tone 3 Tone 1 1 2 3 4 5 6 7 8 9 10 HKU

  21. Identification of tones in context(after Francis, Ciocca, & Ng, in prep) HKU

  22. Pairwise Discrimination(same/different) HKU

  23. Cantonese Tones • Show distinct categories in identification. • Do not show any evidence of category effect on discrimination. • Conclusion (for now): Perception of tone categories does not depend only on changes in perceptual abilities. HKU

  24. Categorical Perception • The use of categories in perception is a cognitive process that involves interaction between perceptual information and higher-level knowledge of objects in the world. HKU

  25. What rules are used to group objects? • Definitions (Feature Lists) • Family Resemblance • Similarity to Prototypes • Exemplar models HKU

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  28. Definitions and Features • Dogs are animals that have four legs, have fur, bark, wag their tails… HKU

  29. Family Resemblance • Ludwig Wittgenstein (1953) proposed that games could not be defined or categorized by features. • Rather, any game shares some resemblance to some (but not all) other games. HKU

  30. Similarity to Prototypes • Rosch (1978). Prototype is a central, average, representation (real or constructed) of a category. • Tokens sufficiently similar to the prototype are considered members of that category. • Memory for specific exemplars. HKU

  31. Exemplar Models • To remember a category, just remember all the members of the category. • Head-filling-up problem. • Evidence for abstractions. HKU

  32. Bibliography • Francis, A. L., Ciocca, V. & Ng, B. K. C. (in prep). On the noncategorical perception of Cantonese tones. • Gibson, E. J. (1969). Principles of Perceptual Learning and Development. New York, Appleton-Century-Crofts. • Goldstone, R. (1998). Perceptual learning. Annual Review of Psychology, 49, 585-612. • Harnad, S. (1987). Psychophysical and cognitive aspects of categorical perception: A critical overview. In Harnad, S. (Ed.) Categorical Perception: The Groundwork of Cognition. Cambridge, MA, The MIT Press. • Hubel, D. H. & Wiesel, T. N. (1959). Receptive fields of single neurones in the cat’s striate cortex. Journal of Physiology, 148, 574-591. • Hubel, D. H. & Wiesel, T. N. (1962). Receptive fields, binocular ineraction, and functional architecture in the cat’s visual cortex. Journal of Physiology, 160, 106-154. • Rosch, E. (1978). Principles of categorization. In Rosch, E. & Lloyd, B. (Eds.) Cognition and Categorization. Hillsdale, NJ, Lawrence Erlbaum Associates. • Wittgenstein, L. (1953). Philosophical Investigations. New York, Macmillan. HKU

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