Categories in the Brain Ling 411 – 14. Variability in functional webs I.Variable ignition II.Variable web structure.

Categories in the Brain Ling 411 – 14

Variability in functional webs I.Variable ignition II.Variable web structure

Variability I – Variable Ignition  When ignition of a web occurs, it does not have to include the entire functional web  Examples: It isn’t necessary to speak about everything one sees Visualization 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 Mention is optional

Ignition of a word web 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 The part of the motor structure that controls the articulation of [dog]

Speaking 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 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 - Visual 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

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 reminded of an object even though it is absent in the environment.” (Pulvermüller 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: the 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 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 Even integers Counties in Texas  Radial Birds Vehicles  Family resemblance Games Furniture  Ill-defined Thought Mind

Phenomena associated with categories 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world 6. Categories and their memberships vary from one language/culture system to another 7. Categories influence thinking, in both appropriate and inappropriate ways

Phenomena associated with categories: 1 1. No small set of defining features (with rare exceptions) The feature-attribute model fails  Works for some mathematical objects, but doesn’t apply to the way people’s cognitive systems apprehend most things  Example: CUP

Phenomena associated with categories: 2 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries Example: 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 prototypicality

Phenomena associated with categories: 3 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members Prototypical  CAR, TRUCK, BUS Peripheral:  AIRPLANE, TOY CAR, RAFT, ROLLER SKATE, etc. Varying degrees of peripherality

Prototypicality phenomena  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 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains ANIMAL – 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 properties

Phenomena associated with categories: 5 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world In the world, everything  is unique  lacks clear boundaries  changes from day to day (even moment to moment) Whorf: “kaleidoscopic flux”

Phenomena associated with categories: 6 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world 6. 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: French: bell

Phenomena associated with categories - 7 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world 6. Categories and their memberships vary from one language/culture system to another 7. Categories influence thinking, in both appropriate and inappropriate ways B.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 information 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 minicolumn acts as a unit  Therefore a person’s linguistic and conceptual system is a network  Every word and every concept is represented as a sub-network Term: functional web (Pulvermüller 2002)

Concepts and percepts: Cortical representation  Percept: one sensory modality Locations are known Auditory: 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 functional 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 adjacent

Hypothesis III(a): Adjacency  Nodes of related function are in adjacent locations More closely related function, more closely adjacent  Examples: Adjacent locations on cat’s paw represented by adjacent cortical locations Similar line orientations represented by adjacent cortical locations

Hypotheses 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  Hypothesis 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 Cardinal nodes of the subwebs

Phenomena associated with categories 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world 6. Categories and their memberships vary from one language/culture system to another 7. 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 represented in the brain REVIEW

Phenomena associated with categories: 1-3 1. No small set of defining features (with rare exceptions) Example: CUP More realistic alternative: radial categories 2. Fuzzy boundaries Example: VEHICLE 3. Prototypical members and peripheral members VEHICLE  Prototypical: CAR, TRUCK, 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 necessary!) 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 nodes The cardinal node

Nodes have activation thresholds  The node will be activated by any of many different combinations of properties  The key word is enough – it takes enough activation from enough properties to satisfy the threshold  The node will be activated to different degrees by different combinations 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 varying 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 weak activation, weakly satisfying the threshold (emus can’t 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 CERAMIC 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 activation from more associated properties  BIRD is strongly connected to the property FLYING Emus and ostriches don’t 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 connections

Phenomena associated with categories: 4 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains ANIMAL – 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 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 can 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 humans, 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  Minicolumn Basic anatomically described unit 70-110 neurons (avg 75-80) Diameter barely more than that of pyramidal cell body (30-50 μ)  Maxicolumn (term used by Mountcastle) Diameter 300-500 μ Bundle of about 100 continuous minicolumns  Hypercolumn – up to 1 mm diameter Can be long and narrow rather than cylindrical  Functional column Intermediate between minicolumn and maxicolumn A contiguous group of minicolumns

Functional Columns  Intermediate in size between minicolumn and maxicolumn  Hypothesized functional unit whose size is determined by experience/learning  A maxicolumn consists of multiple functional columns  A functional column consists of multiple minicolumns  Functional column may be further subdivided with learning of finer distinctions

Columns of different sizes In order according to size  Minicolumn The smallest unit 70-110 neurons  Functional column Variable size – depends on experience Intermediate between minicolumn and maxicolumn  Maxicolumn (a.k.a. column) 100 to a few hundred minicolumns  Hypercolumn Several contiguous maxicolumns

Hypercolums: Modules of maxicolumns A visual area in temporal lobe of a macaque monkey

Perceptual subcategories and columnar subdivisions of larger columns  Nodal specificity applies for maxicolumns as well as for minicolumns  The adjacency hypothesis likewise applies to larger categories and columns Adjacency applies for adjacent maxicolumns  Subcategories of a category have similar function Therefore their cardinal nodes should be in adjacent locations

Functional columns  The minicolumns within a maxicolumn respond to a common set of features  Functional columns are intermediate in size between minicolumns and maxicolumns  Different functional columns within a maxicolumn are distinct because of non- shared additional features Shared within the functional column Not shared with the rest of the maxicolumn Mountcastle: “The neurons of a [maxi]column have certain sets of static and dynamic properties in common, upon which others that may differ are superimposed.”

Similarly..  Neurons of a hypercolumn may have similar response features, upon which others that differ may be superimposed  Result is maxicolumns in the hypercolumn sharing certain basic features while differing with respect to others  Such maxicolumns may be further subdivided into functional columns on the basis of additional features  That is, columnar structure directly maps categories and subcategories

Hypercolums: Modules of maxicolumns A visual area in the temporal lobe of a macaque monkey Category (hypercolumn) Subcategory (can be further subdivided)

Category representations in the cortex  Hypercolumn  Maxicolumn  Functional column  Sub-functional column  Supercategory  Category  Subcategory  Sub-subcategory

Hypothesis applied to conceptual categories  A whole maxicolumn gets activated for a category Example: BEAR  Different functional columns within the maxicolumn for subcategories BROWN BEAR, GRIZZLY, POLAR BEAR, etc.  Adjacent maxicolumns for categories related to BEAR (sharing various features) I.e., other carnivores  Similarly, CUP has a column surrounded by columns for other drinking vessels

Phenomena associated with categories: 5 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world In the world, everything  is unique  lacks clear boundaries  changes from day to day (even moment to moment) Whorf: “kaleidoscopic flux”

Phenomena associated with categories: 6 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world 6. 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: French: bell REVIEW

Phenomena associated with categories - 7 1. No small set of defining features (with rare exceptions) 2. Fuzzy boundaries 3. Prototypical members and peripheral members 4. Subcategories, and sub-subcategories, in hierarchical chains 5. Categories are in the mind, not in the real world 6. Categories and their memberships vary from one language/culture system to another 7. Categories influence thinking, in both appropriate and inappropriate ways B.L. Whorf Example: Racial profiling

These phenomena (5-7) are interrelated 5. Categories are in the mind, not in the real world 6. Categories and their memberships vary from one language/culture system to another 7. Categories influence thinking, in both appropriate and inappropriate ways B.L. Whorf Example: Racial profiling

Pertinent neuroanatomical findings: Bidirectional Processing  An established fact of neuroanatomy: A connection from point A to point B in the cortex is generally accompanied by a connection from point B to point A  Separate fibers (axons): (1) A to B, (2) B to A  In short, cortico-cortical connections are generally bidirectional

Bidirectional processing and inference T CUP MADE OF GLASS CERAMIC SHORT HANDLE These connections are bidirectional Separate fibers for the two directions; shown as one line in the notation

Bidirectional processing and inference T CUP SHORT HANDLE Thought process: 1. The cardinal concept node is activated by a subset of its property nodes 2. Feed-backward processing activates other property nodes Consequence: We “apprehend” properties that are not actually perceived

Category Structure and Inference T Category Properties A B F E Consequence: If A and B, then E and F C D

Examples  Looks like a duck Probably quacks  Ceramic, cup-shaped, handle Probably holds coffee (without breaking)  Dark clouds, thunder It’s going to rain  ATM Probably has money

Another hypothesis of Whorf  Grammatical categories of a language influence the thinking of people who speak the language  Can we explain this too in terms of brain structure?

Mechanisms of operation 1. Entrenchment Strengthening of connections through repeated activation An automatic brain process Important in learning 2. Reverberation of activation Leads to greater levels of activation 3. Priming 4. Language as a major means of learning conceptual and perceptual distinctions

Entrenchment and thinking: a mechanism  Connections become stronger with use (entrenchment)  Grammatical categories make speakers constantly heed selected phenomena  Connections for phenomena which speakers must constantly heed.. Will be repeatedly traversed Therefore will get progressively stronger

Thinking: Reverberating Activation  Speaking and thinking in English: Reverberating activation among categories and images of English  Thinking in German or Spanish or Yucatec Reverberating activation among categories and images of German or Spanish or Yucatec “When I speak Indian, I think differently” Wallace Chafe’s Oneida informant

Example: Grammatical gender  Does talking about inanimate objects as if they were masculine or feminine actually lead people to think of inanimate objects as having a gender?  Could the grammatical genders assigned to objects by a language influence people’s mental representation of objects? Boroditsky (2003)

Plausibility of the possibility  Children learning to speak a language with grammatical gender may suppose that gender indicates a meaningful distinction between types of objects  Other grammatical distinctions do reflect actual perceptual differences: singular:plural

Children learning a language with gender  “For all they know, the grammatical genders assigned by their language are the true universal genders of objects.” Boroditsky et al, 2003

Experiment: Gender and Associations (Boroditsky et al. 2002)  Subjects: speakers of Spanish or German All were fluent also in English English used as language of experiment  Task: Write down the 1 st 3 adjectives that come to mind to describe each object All the (24) objects have opposite gender in German and Spanish  Raters of adjectives: Native English speakers

Examples:  Key (masc in German, fem in Spanish) Adjectives used by German speakers:  Hard, heavy, jagged, metal, serrated, useful Adjectives used by Spanish speakers:  Golden, intricate, little, lovely, shiny, tiny  Bridge (fem in German, masc in spanish) Adjectives used by German speakers:  Beautiful, elegant, fragile, peaceful, pretty Adjectives used by Spanish speakers:  Big, dangerous, long, strong, sturdy, towering

Results of the Experiment (Boroditsky et al. 2002)  Raters of adjectives were native English speakers  Result: Adjectives were rated as masculine or feminine in agreement with the gender in subject’s native language

In conclusion.. All of these phenomena associated with categories (briefly reviewed in this presentation) can be explained as inevitable consequences of the structure and function of the human brain

Categories in the Brain Ling 411 – 14. Variability in functional webs I.Variable ignition II.Variable web structure.

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Categories in the Brain Ling 411 – 14. Variability in functional webs I.Variable ignition II.Variable web structure.

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Presentation on theme: "Categories in the Brain Ling 411 – 14. Variability in functional webs I.Variable ignition II.Variable web structure."— Presentation transcript:

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