creators_name: Pevtzow, Rachel creators_name: Harnad, Stevan editors_name: Ramscar, M. editors_name: Hahn, U. type: bookchapter datestamp: 2001-06-19 lastmod: 2011-03-11 08:54:42 metadata_visibility: show title: Warping Similarity Space in Category Learning by Human Subjects: The Role of Task Difficulty ispublished: pub subjects: percep-cog-psy full_text_status: public keywords: categorical perception, acquired similarity, symbol grounding, acquired distinctiveness, perceptual learning abstract: In innate Categorical Perception (CP) (e.g., colour perception), similarity space is "warped," with regions of increased within-category similarity (compression) and regions of reduced between-category similarity (separation) enh ancing the category boundaries and making categorisation reliable and all-or-none rather than graded. We show that category learning can likewise warp similarity space, resolving uncertainty near category boundaries. Two Hard and two Easy texture learning tasks were compared: As predicted, there were fewer successful Learners with the Hard task, and only the successful Learners of the Hard task exhibited CP. In a second experiment, the Easy task was made Hard by making the corrective feedback during learn ing only 90% reliable; this too generated CP. The results are discussed in relation to supervised, unsupervised and dual-mode models of category learning and representation.The world is full of things that vary in their similarity and interconfusability.O rganisms must somehow resolve this confusion, sorting and acting upon things adaptively. It might be important, for example, to learn which kinds of mushrooms are poisonous and which are safe to eat, minimising the confusion between them (Greco, Cangelosi & Harnad 1997). date: 1997 date_type: published publication: Proceedings of SimCat 1997: Interdisciplinary Workshop on Similarity and Categorization publisher: Department of Artificial Intelligence, Edinburgh University pagerange: 189-195 refereed: FALSE referencetext: Andrews, J., Livingston, K. & Harnad, S. (in press) Categorical Perception Effects Induced by Category Learning. Journal of Experimental Psychology: Human Learning and Cognition . Andrews, J., Livingston, K., Harnad, S. & Fischer, U. (1994) Are Concepts Grounded in Categorical Perception? Some Relevant Em pirical Results. Presented at Annual Meeting of Society for Philosophy and Psychology. Memphis TN, June 1994 Beale, J.M., & Keil, F.C. (1996). Categorical perception as an acquired phenomenon: What are the implications? In L. Smith & P. Hancock (Eds.). 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(1987) Auditory, Arti culatory and Learning Explanations of Categorical Perception in Speech. In Harnad (1987) Stevenage, S.V. (1997) Which Twin Are You? A Demonstration of Induced Categorical Perception of Identical Twin Faces. British Journal of Psychology (in pre ss) Tijsseling, A. & Harnad, S. (1997) Warping Similarity Space in Category Learning by BackProp Nets. Interdisciplinary Workshop On Similarity And Categorisation, Edinburgh, Scotland, November 1997 Young, A.W., Rowland, D., Calder, A.J., Etcof f, N.L., Seth, A., & Perrett, D.I. (1997). Facial expression Megamix: Tests of dimensional and category accounts of emotion recognition. Cognition , 63 : 271-313. citation: Pevtzow, Rachel and Harnad, Stevan (1997) Warping Similarity Space in Category Learning by Human Subjects: The Role of Task Difficulty. [Book Chapter] document_url: http://cogprints.org/1607/1/harnad97.textures.html