Advanced Topics: Categorical Perception (CP)

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The most familiar example of categorical perception (CP), is unfortunately associated with an ethnic stereotype: It has been called (by Americans) the "Chinese-Waiter" effect, but of course it might just as well have been called by the Chinese the "American-Waiter" effect! It concerns the fact that, to Americans living in America, all Chinese waiters seem to look alike, whereas American waiters all look individual and distinct. A similar well-known example of CP (though it is actually not valid, as will be explained in class) is that of Eskimo words for snow: Allegedly, Eskimos see many distinct kinds of snow where we just see that one uniform white stuff. Another celebrated example is color terms: Which colors will look different and which colors will look alike to you depends on which culture you are in and which language you speak. A last example is language itself: Native speakers of a language can hear and produce differences in sounds (phonemes) that to a non-native sound alike (and are unpronouncable). All these are instances of CP.

This CP phenomenon -- the compression and expansion of similarities and differences among objects, depending on whether they belong to the same category (in which case they look similar) or to different categories (in which case they look different) -- has an interesting history, occurs in many very different domains (sight, vision, language, social perception -- even animals have it), and is now coming to be understood better as its relation to the categories we are born with and the ones we learn is experimentally studied in people and animals, modelled on computers, and investigated in the brain.

There are four subtopics, and three sample questions on each. The sample questions may be chosen for your essay question, if you decide to write an essay, and they are also the kind of question that will appear in the examination. Your 20-minute joint paper can be based on any aspect of your subtopic. Most readings can come from "Categorical Perception: The Groundwork of Cognition" (S. Harnad, ed., Cambridge University Press 1987) Nine copies are available on short loan; one can be taken out for a week [(BRN 69170) Hartley Library BF 311 HAR 88054588]. More references (optional) are listed with each sample question. Your subtopic and readings can be discussed with me.

Each subtopic will give you a deeper understanding of one aspect of CP, while tying it together with other, related aspects. A full picture will emerge as those working on each subtopic fill in their portion of the CP landscape. The readings will overlap, and so should your own efforts, in working on your questions.

A Subject-coded version of this reading list is also retrievable. Use it to pick out which papers you want to read in preparing your reports, based on your topic, interest and the availability of the papers. The full reading list with abstracts can also be retrieved through www. Choose from among those. Papers by me are directly retrievable through www; the others you must find in the library.

I. Human visual and social categories (color, form, social judgment)

The CP story seems to differ from sense to sense: seeing differs from hearing, and even within hearing, speech differs from nonspeech. Then there are multisensory categories, such as complex objects, people, and social judgments about people. And eventually there are the abstract categories (goodness, truth and beauty) that leave all sensory modalities and concrete objects behind.

Ia. Are color categories innate or learned?

Do colors look the way they do because we have learned to classify them as we do, or because we were born seeing them that way? The evidence is mixed. As you sort out this special case, you will get a better idea about many aspects of categorisation in general.

Bornstein, Marc H. Perceptual categories in vision and audition. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 287-300.

Zollinger, Heinrich. Categorical color perception: Influence of cultural factors on the differentiation of primary and derived basic color terms in color naming by Japanese children. Vision Research, 1988, v28 (n12):1379-1382.

Boynton, Robert M. Color vision. IN: Annual review of psychology, Vol. 39. Annual review of psychology.; Mark R. Rosenzweig, Lyman W. Porter, Eds. Annual Reviews, Inc, Palo Alto, CA, US. 1988. p. 69-100.

Berlin, B. & Kay, P. (1969) Basic color terms: Their universality and evolution. Berkeley: University of California Press

Ib. What is the current status of the "Whorf Hypothesis" (according to which our language and culture determine the way we see the world)?

Whorf thought that language and culture determined how things look to us, but is that true? or was Whorf just a bad linguist? Again, there seems to be evidence in both directions, and sorting it out will put more of the categorisation problem into prespective.

Feldman, Jack. Objects in categories and objects as categories. IN: A dual process model of impression formation. Advances in social cognition, Vol. 1.; Thomas K. Srull, Robert S. Wyer Jr., Eds. Lawrence Erlbaum Associates, Inc, Hillsdale, NJ, US. 1988. p. 53-63.

Tajfel, Henri. The structure of our views about society. IN: Introducing social psychology: An analysis of individual reaction and response.; Henri Tajfel, Colin Fraser, Eds. Penguin Books, Inc, Middlesex, England. 1978. p. 302-321.

Pullum, G. K. (1989) The great eskimo vocabulary hoax. Natural Language and Ling uistic Theory 7: 275-281.

Whorf, B. L. (1964) Language, thought and reality. Cambridge MA: MIT Press

Ic. Is there something special about spatial categories?

Space is continuous, rather than categorical, yet we have spatial categories, some of them continuous (e.g., near/far) but some of them more categorical (above/below). Is space special? The question has interesting parallels and contrasts with the question: Is speech special (IIa).

Quinn, Paul C. The categorization of above and below spatial relations by young infants. Child Development, 1994 Feb, v65 (n1):58-69.

Kosslyn, Stephen M.; Koenig, Olivier; Barrett, Anna; Cave, Carolyn B.; and others. Evidence for two types of spatial representations: Hemispheric specialization for categorical and coordinate relations. Journal of Experimental Psychology: Human Perception & Performance, 1989 Nov, v15 (n4):723-735.

Bialystok, Ellen; Olson, David R. Spatial categories: The perception and conceptualization of spatial relations. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 511-531.

Bomba, Paul C. The development of orientation categories between 2 and 4 months of age. Journal of Experimental Child Psychology, 1984 Jun, v37 (n3):609-636.

II. Human auditory categories (speech, music, rhythm, time)

Even within the modality of hearing, there are many interesting variations and differences. Speech vs. nonspeech is an important one, but so is the difference between percetion and production (the "motor" theory), and that special form of "language" called music.

IIa. Is Speech Special?

The CP phenomenon of was first discovered in speech perception: Variants of the same phoneme, the smallest functional unit in language, all sound alike to us, whereas different phonemes sound very different. This raises the question of whether speech signals are processed in a special way, unlike nonspeech acoustic signals. Again, the evidence goes in both directions, and sorting it out will cast light on still further dimensions of CP.

Schouten, M. E.; Van Hessen, A. J. Modeling phoneme perception: I. Categorical perception. Journal of the Acoustical Society of America, 1992 Oct, v92 (n4, Pt 1):1841-1855.

Rosen, Stuart; Howell, Peter. Auditory, articulatory, and learning explanations of categorical perception in speech. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 113-160.

Kuhl, Patricia K. The special-mechanisms debate in speech research: Categorization tests on animals and infants. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 355-386.

Lane, H. (1965) The motor theory of speech perception: A critical review. Psychological Review 72: 275 - 309.

IIb. What is the current status of the "Motor Theory of Speech Perception"?

CP's origins are also tied to the "motor theory" of speech perception, according to which the similarities and differences between speech sounds are determined for our ears by how our mouths would have produced them. This theory has fallen on hard times, but is there still some truth to it? Evidence from preverbal children, animals, and other sensory modalities will have to be weighed in your reply.

Kuhl, Patricia K. Perception, cognition, and the ontogenetic and phylogenetic emergence of human speech. IN: Plasticity of development.; Steven E. Brauth, William S. Hall, Robert J. Dooling, Eds. MIT Press, Cambridge, MA, US. 1991. p. 73-106.

Repp, Bruno H.; Liberman, Alvin M. Phonetic category boundaries are flexible. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 89-112.

Studdert-Kennedy, Michael; Liberman, Alvin M.; Harris, Katherine S.; Cooper, Franklin S. Motor theory of speech perception: A reply to Lane's critical review. Psychological Review, 1970, v77 (n3):234-249.

Lane, H. (1965) The motor theory of speech perception: A critical review. Psychological Review 72: 275 - 309.

IIc. Is music perceived categorically?

Music has many similarities to speech; does it share CP too? Music is a very interesting test case, because it is less likely than speech to have inborn feature detectors already "prepared" by evolution; and it does not, like speech, convey a literal message. Yet there are parallels too. Absolute pitch, rhythm perception and harmony are among the variables to look at here.

Howard, David M.; Rosen, Stuart; Broad, Victoria. Major/minor triad identification and discrimination by musically trained and untrained listeners. Music Perception, 1992 Winter, v10 (n2):205-220.

Lynch, Michael P.; Eilers, Rebecca E.; Bornstein, Marc H. Speech, vision, and music perception: Windows on the ontogeny of mind. Special Issue: Child development and music. Psychology of Music, 1992, v20 (n1):3-14.

Krumhansl, Carol L. Music psychology: Tonal structures in perception and memory. IN: Annual review of psychology, Vol. 42. Annual review of psychology.; Mark R. Rosenzweig, Lyman W. Porter, Eds. Annual Reviews, Inc, Palo Alto, CA, US. 1991. p. 277-303.

Siegel, Jane A.; Siegel, William. Categorical perception of tonal intervals: Musicians can't tell sharp from flat. Perception & Psychophysics, 1977 May, v21 (n5):399-407.

III. Nonhuman animals' categories (feature detectors, animal communication)

Many of the questions about CP extend beyond our species to animal communication and signalling in general, hence to the origins of human categories. Animals also give some clues about how to sort out the effects of learning from the effects of inborn feature detectors.

IIIa. Review the evidence for continuous vs. categorical perception and production of animals' signals.

Animals too have continuous and discontinuous signalling systems; these share some of the properties of CP, but here the question of what is special about speech CP joins the more general question of what is special about language itself.

Snowdon, Charles T. Linguistic phenomena in the natural communication of animals. IN: Language and communication: Comparative perspectives. Comparative cognition and neuroscience.; Herbert L. Roitblat, Louis M. Herman, Paul E. Nachtigall, Eds. Lawrence Erlbaum Associates, Inc, Hillsdale, NJ, US. 1993. p. 175-194.

Hopp, Steven L.; Sinnott, Joan M.; Owren, Michael J.; Petersen, Michael R. Differential sensitivity of Japanese macaques (Macaca fuscata) and humans (Homo sapiens) to peak position along a synthetic coo call continuum. Journal of Comparative Psychology, 1992 Jun, v106 (n2):128-136.

Nelson, Douglas A.; Marler, Peter. Categorical perception of a natural stimulus continuum: Birdsong. Science, 1989 May, v244 (n4907):976-978.

Ehret, Gunter. Categorical perception of sound signals: Facts and hypotheses from animal studies. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 301-331.

IIIb. What evidence is there that learning can produce categorical perception in animals?

In many ways the most interesting CP effects are those that are produced by learning something, rather than by being born with categorical feature detectors. It is only lately that animal learning is beginning to be investigated from a CP standpoint and the findings are intriguing.

Herrnstein, Richard J. Levels of stimulus control: A functional approach. Special Issue: Animal cognition. Cognition, 1990 Nov, v37 (n1-2):133-166.

Honig, W. K.; Stewart, Karen E. Discrimination of relative numerosity by pigeons. Animal Learning & Behavior, 1989 May, v17 (n2):134-146.

Pepperberg, Irene M. Acquisition of the same/different concept by an African Grey parrot ( Psittacus erithacus ): Learning with respect to categories of color, shape, and material. Animal Learning & Behavior, 1987 Nov, v15 (n4):423-432.

Zentall, Thomas R.; Jackson-Smith, Pamela; Jagielo, Joyce A.; Nallan, Gary B. Categorical shape and color coding by pigeons. Journal of Experimental Psychology: Animal Behavior Processes, 1986 Apr, v12 (n2):153-159.

IIIc. Do feature detectors produce categorical perception?

Where there is CP, it is natural to asks what internal mechanism causes it. Inborn feature detectors that "bias" how we see things are one candidate. But can "feature-detectors" also be acquired through learning?

Martin KA. A brief history of the "feature detector". Cerebral Cortex, 1994 Jan-Feb, 4(1):1-7.

Harnad, S. Hanson, S.J. & Lubin, J. (1994) Learned Categorical Perception in Neural Nets: Implications for Symbol Grounding. In: V. Honavar & L. Uhr (eds) Symbol Processors and Connectionist Network Models in Artificial Intelligence and Cognitive Modelling: Steps Toward Principled Integration. Academic Press.

Anderson, James A.; Silverstein, Jack W.; Ritz, Stephen A.; Jones, Randell S. Distinctive features, categorical perception, and probability learning: Some applications of a neural model. IN: Neurocomputing: Foundations of research.; James A. Anderson, Edward Rosenfeld, Eds. MIT Press, Cambridge, MA, US. 1988. p. 287-325.

Diehl, Randy L. Feature detectors for speech: A critical reappraisal. Psychological Bulletin, 1981 Jan, v89 (n1):1-18.

IV. Brain correlates and computer models of categorization (brain activity, pattern recognition, neural nets)

CP can be analysed behaviorally, by studying the way people discriminate and identify different stimuli, both naturally and as an outcome of learning. But at some point it is natural to ask: HOW do we manage to discriminate and identify things as we do? Clues come from brain function as well as from computer modelling.

IVa. Is Categorical Perception related to left/right differences in the brain?

Some of the behavioral findings on CP as well as some of the explanatory models have been linked to the well-known left/right asymmetry of the brain. Again, this is not the whole story, but it provides some interesting pieces of it.

Rybash, John M.; Hoyer, William J. Hemispheric specialization for categorical and coordinate spatial representations: A reappraisal. Memory & Cognition, 1992 May, v20 (n3):271-276.

Molfese, Dennis L.; Molfese, Victoria J. Right-hemisphere responses from preschool children to temporal cues to speech and nonspeech materials: Electrophysiological correlates. Brain & Language, 1988 Mar, v33 (n2):245-259.

Kosslyn, Stephen M., ed.; Andersen, Richard A., ed. Frontiers in cognitive neuroscience. MIT Press; Cambridge, MA, US, 1992.

IVb. Compare the various models that have been proposed to explain categorical percption.

Different models for CP exist, some very specialized, some quite general. Some are computational, some just conceptual; some are related to brain functioning, some to general principles of sorting and classifying things. You must assess their relative strengths and weaknesses.

Harnad, S. (1992) Connecting Object to Symbol in Modeling Cognition. In: A. Clarke and R. Context Springer Verlag.

Commons, Michael L., ed.; Herrnstein, Richard J., ed.; Kosslyn, Stephen M., ed.; Mumford, David B., ed. Behavioral approaches to pattern recognition and concept formation. Lawrence Erlbaum Associates, Inc; Hillsdale, NJ, US, 1990. Series title: Quantitative analyses of behavior, Vol. 8.

Pastore, Richard E. Categorical perception: Some psychophysical models. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 29-52.

Macmillan, Neil A. Beyond the categorical/continuous distinction: A psychophysical approach to processing modes. IN: Categorical perception: The groundwork of cognition.; Stevan Harnad, Ed. Cambridge University Press, New York, NY, US. 1987. p. 53-85.

IVc. How might categorical perception be related to the rest of cognition (thinking, reasoning, language)?

This is the question that requires you to draw it all together. There are many possible answers. CP might be special, related only to a few special cases of sensory processing, like speech and color. Or it may be general, related to all of categorisation and cognition.

Harnad, S. (1993) The Origin of Words: A Psychophysical Hypothesis. To appear in Durham, W & Velichkovsky B (Eds.) "Naturally Human: Origins and Destiny of Language."

Kosslyn, Stephen M., ed.; Andersen, Richard A., ed. Frontiers in cognitive neuroscience. MIT Press; Cambridge, MA, US, 1992.

Marler, Peter. Social organization, communication and graded signals: The chimpanzee and the gorilla. IN: Growing points in ethology. Cambridge, England: Cambridge U Press, 1976.

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