Categories in the Brain.ppt

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1、Categories in the Brain,Ling 411 14,Variability in functional webs,Variable ignitionVariable web structure,Variability I Variable Ignition,When ignition of a web occurs, it does not have to include the entire functional web Examples: It isnt necessary to speak about everything one sees Visualization

2、 is optional At least to some extent Application of attention can provide richer detail of ignition More extensive activation of subwebs For example, visualization,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word w

3、eb from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from vi

4、sual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Ignition of a word web from visual input,V,P,PA,M,C,Art,T,Mention is optional,Ignition of a word w

5、eb from visual input,V,P,PA,M,C,Art,T,Speaking as a response to ignition of a web,V,P,PA,M,C,Art,T,Speaking as a response to ignition of a web,V,P,PA,M,C,Art,T,Speaking as a response to ignition of a web,V,P,PA,M,C,Art,T,The part of the motor structure that controls the articulation of dog,Speaking

6、as a response to ignition of a web,V,P,PA,M,C,Art,T,From here to the muscles that control the organs of articulation,Ignition of a web from speech input,V,PA,M,C,Properties:C Conceptual M Memories PR Phonolog. Rec. T Tactile V - Visual,T,PR,Ignition of a web from speech input,V,PA,M,C,Properties:C C

7、onceptual M Memories PR Phonolog. Rec. T Tactile V - Visual,T,PR,Ignition of a web from speech input,V,PR,PA,M,C,Properties:C Conceptual M Memories P Phonolog. Rec. T Tactile V - Visual,T,Ignition of a web from speech input,V,PA,M,C,Properties:C Conceptual M Memories PR Phonol. Rec. T Tactile V - Vi

8、sual,T,PR,Ignition of a web from speech input,V,PA,M,C,T,PR,Upon hearing “cat” we can also visualize a cat Probably a largely optional process,Visualization from speech input,V,PA,M,C,T,PR,Upon hearing “cat” we can also visualize a cat,V,PA,M,C,T,PR,Visualization from speech input,V,PA,M,C,T,PR,Visu

9、alization from speech input,V,PA,M,C,T,PR,Visualization from speech input,Cortex-internal ignition,“ ignition of the web after sufficiently strong stimulation by cortical neurons outside the functional web. This cortex-internal activation of a web can be considered the organic basis of being reminde

10、d of an object even though it is absent in the environment.”(Pulvermller 2002: 30),Variability II Variable web structure,Observation: every cat perceived or spoken about is different from others encountered previously For example, different color Each web is built based on experience Consequence: th

11、e precise web structure for an individual is likely to differ in details for different instances of the same category Inertia: some of the differences in a new exemplar are likely to be overlooked,Some Key Concepts,Functional Web (Functional) Subweb Cardinal node Ignition Reverberation,Understanding

12、 semantics,Semantic structure is largely a matter of conceptual categories Understanding how categories work is the key to unlock the mysteries of semantics To understand how categories work we need to understand how the brain manages categorial information,Types of Conceptual Categories,Discrete Ev

13、en integers Counties in Texas Radial Birds Vehicles Family resemblance Games Furniture Ill-defined Thought Mind,Phenomena associated with categories,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral members Subcategories, and sub-subcategor

14、ies, in hierarchical chains Categories are in the mind, not in the real world Categories and their memberships vary from one language/culture system to another Categories influence thinking, in both appropriate and inappropriate ways,Phenomena associated with categories: 1,No small set of defining f

15、eatures (with rare exceptions) The feature-attribute model fails Works for some mathematical objects, but doesnt apply to the way peoples cognitive systems apprehend most things Example: CUP,Phenomena associated with categories: 2,No small set of defining features (with rare exceptions) Fuzzy bounda

16、riesExample: VEHICLE Car, truck, bus Airplane? Boat? Toy car, model airplane? Raft? Roller skate? Snowboard?,Fuzzy Categories,No fixed boundaries Membership comes in degrees Prototypical Less prototypical Peripheral Metaphorical The property of fuzziness relates closely to the phenomenon of prototyp

17、icality,Phenomena associated with categories: 3,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral membersPrototypicalCAR, TRUCK, BUS Peripheral: AIRPLANE, TOY CAR, RAFT, ROLLER SKATE, etc. Varying degrees of peripherality,Prototypicality ph

18、enomena,The category BIRD Some members are prototypical ROBIN, SPARROW Others are peripheral EMU, PENGUIN The category VEHICLE Prototypical: CAR, TRUCK, BUS Peripheral: ROLLER SKATE, HANG GLIDER,Phenomena associated with categories: 4,No small set of defining features (with rare exceptions) Fuzzy bo

19、undaries Prototypical members and peripheral members Subcategories, and sub-subcategories, in hierarchical chainsANIMAL MAMMAL CARNIVORE CANINE DOG TERRIER JACK RUSSELL TERRIER EDDIE Each subcategory has the properties of the category plus additional properties Smallest subcategory has the most prop

20、erties,Phenomena associated with categories: 5,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral members Subcategories, and sub-subcategories, in hierarchical chains Categories are in the mind, not in the real worldIn the world, everything

21、is unique lacks clear boundaries changes from day to day (even moment to moment) Whorf: “kaleidoscopic flux”,Phenomena associated with categories: 6,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral members Subcategories, and sub-subcategor

22、ies, in hierarchical chains Categories are in the mind, not in the real world Categories and their memberships vary from one language/culture system to another,cloche (of a church) clochette (on a cow) sonnette (of a door) grelot (of a sleigh) timbre (on a desk) glas (to announce a death),English: F

23、rench:bell,Phenomena associated with categories - 7,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral members Subcategories, and sub-subcategories, in hierarchical chains Categories are in the mind, not in the real world Categories and thei

24、r memberships vary from one language/culture system to another Categories influence thinking, in both appropriate and inappropriate waysB.L. Whorf Example: Racial profiling,Beyond description to explanation,How can we explain these phenomena? To answer this question we have to examine how our inform

25、ation about categories is represented in the brain The brain is where our linguistic and cultural knowledge is represented,Facts and hypotheses that we can build on,The brain is a network Composed, ultimately, of neurons Cortical neurons are clustered in columns Columns come in different sizes Each

26、minicolumn acts as a unit Therefore a persons linguistic and conceptual system is a network Every word and every concept is represented as a sub-network Term: functional web (Pulvermller 2002),Concepts and percepts: Cortical representation,Percept: one sensory modality Locations are known Auditory:

27、temporal lobe Visual: occipital lobe Somatosensory: parietal lobe Concept: more than one sensory modality Higher level (more abstract) Locations, for nominal concepts: Angular gyrus (?)MTG (?)SMG,Hypotheses concerning functional webs,Hypothesis I: Functional Webs A concept is represented as a functi

28、onal web Hypothesis II: Columnar Nodes Nodes are implemented as cortical columns Hypothesis III: Nodal Specificity Every node in a functional web has a specific function Hypothesis III(a): Adjacency Nodes of related function are in adjacent locations More closely related function, more closely adjac

29、ent,Hypothesis III(a): Adjacency,Nodes of related function are in adjacent locations More closely related function, more closely adjacent Examples: Adjacent locations on cats paw represented by adjacent cortical locations Similar line orientations represented by adjacent cortical locations,Hypothese

30、s concerning functional webs,Hypothesis IV: Extrapolation to Humans The findings about cortical structure and function from experiments on cats, monkeys, and rats can be extrapolated to humans Hypothesis IV(a): The extrapolation can be extended to linguistic and conceptual structures and functions H

31、ypothesis V: Hierarchy A functional web is hierarchically organized Hypothesis VI: Cardinal nodes Every functional web has a cardinal node Hypotheses VI(a): Each subweb likewise has a cardinal node,(Part of) the functional web for CAT,V,P,A,M,C,The cardinal node for the entire functional web,T,Cardi

32、nal nodes of the subwebs,Phenomena associated with categories,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral members Subcategories, and sub-subcategories, in hierarchical chains Categories are in the mind, not in the real world Categorie

33、s and their memberships vary from one language/culture system to another Categories influence thinking, in both appropriate and inappropriate ways,REVIEW,How to explain?,Description is fine, but its only a start Next step: Explanation How to explain? By answering the question of how categories are r

34、epresented in the brain,REVIEW,Phenomena associated with categories: 1-3,No small set of defining features (with rare exceptions) Example: CUP More realistic alternative: radial categories Fuzzy boundaries Example: VEHICLE Prototypical members and peripheral members VEHICLE Prototypical:CAR, TRUCK,

35、BUS Peripheral: AIRPLANE, TOY CAR, RAFT, ROLLER SKATE, etc. Varying degrees of peripherality These three phenomena are interdependent,How do radial categories work?,Different connections have different strengths (weights) More important properties have greater strengths For CUP, Important (but not n

36、ecessary!) properties: Short (as compared with a glass) Ceramic Having a handle Cups with these properties are more prototypical,The properties of a category have different weights,T,CUP,MADE OF GLASS,CERAMIC,SHORT,HAS HANDLE,The properties are represented by nodes which are connected to lower-level

37、 nodes,The cardinal node,Nodes have activation thresholds,The node will be activated by any of many different combinations of propertiesThe key word is enough it takes enough activation from enough properties to satisfy the thresholdThe node will be activated to different degrees by different combin

38、ations of properties When strongly activated, it transmits stronger activation to its downstream nodes.,Prototypical exemplars provide stronger and more rapid activation,T,CUP,MADE OF GLASS,CERAMIC,SHORT,HAS HANDLE,Stronger connections carry more activation,Activation threshold(can be satisfied to v

39、arying degrees),Inhibitory connection,Explaining Prototypicality,Cardinal category nodes get more activation from the prototypical exemplars More heavily weighted property nodes E.g., FLYING is strongly connected to BIRD Property nodes more strongly activated Peripheral items (e.g. EMU) provide only

40、 weak activation, weakly satisfying the threshold (emus cant fly) Borderline items may or may not produce enough activation to satisfy threshold,Activation of different sets of properties produces greater or lesser satisfaction of the activation threshold of the cardinal node,CUP,MADE OF GLASS,CERAM

41、IC,SHORT,HAS HANDLE,More important properties have stronger connections, indicated here by thickness of lines,Explaining prototypicality: Summary,Variation in strength of connections Many connecting properties of varying strength Varying degrees of activation Prototypical members receive stronger ac

42、tivation from more associated properties BIRD is strongly connected to the property FLYING Emus and ostriches dont fly But they have some properties connected with BIRD Sparrows and robins do fly And as commonly occurring birds they have been experienced often, leading to entrenchment stronger conne

43、ctions,Phenomena associated with categories: 4,No small set of defining features (with rare exceptions) Fuzzy boundaries Prototypical members and peripheral members Subcategories, and sub-subcategories, in hierarchical chains ANIMAL MAMMAL CARNIVORE CANINE DOG TERRIER JACK RUSSELL TERRIER EDDIE Each

44、 subcategory has the properties of the category plus additional properties Smallest subcategory has the most properties,How to explain? Perceptual Neuroscience,We have evidence on this point from the experiments described by Mountcastle Hypothesis IV: Extrapolation Hypothesis IV(a): Extrapolation ca

45、n be extended to linguistic and conceptual structures Why? Cortical structure, viewed locally, is Uniform across mammalian species Uniform across different cortical regions Cortical structure and function, locally, are essentially the same in humans as in cats and monkeys and rats Moreover, in human

46、s, the regions that support language have the same structure locally as other cortical regions,Conceptual systems and perceptual systems,Conceptual systems in humans evidently use the same structures as perceptual systems Therefore it is not too great a stretch to suppose that experimental findings on the structure of perceptual systems in monkeys can be applied to an understanding of the structure of conceptual systems of human beings In particular to the structures of conceptual categories,REVIEW,Columns of different sizes,