Category-Specific Deficits Category-Specific Deficits and Implications for the and Implications for the Structure of Conceptual Structure of Conceptual

KnowledgeKnowledge

David PriceDavid Price

Basic Facts/TrendsBasic Facts/Trends Distinguishing features of category-specific Distinguishing features of category-specific

deficitsdeficits::

1.1. Patients seemingly exhibit disproportionate and selective Patients seemingly exhibit disproportionate and selective impairment of knowledge of one category of objects v. impairment of knowledge of one category of objects v. other categoriesother categories

2.2. Most studies of instances of category-specific deficits Most studies of instances of category-specific deficits involve sparing or selective impairment of ‘living things’, involve sparing or selective impairment of ‘living things’, ‘non-living things’, ‘animals’, ‘fruits/vegetables’, and ‘non-living things’, ‘animals’, ‘fruits/vegetables’, and ‘artifacts’ ‘artifacts’

3.3. Unclear as to whether instances of category-specific Unclear as to whether instances of category-specific deficits are a result of damage to a categorically-deficits are a result of damage to a categorically-organized semantic system, or damage to specific organized semantic system, or damage to specific modality of knowledge (e.g. visual or functional)modality of knowledge (e.g. visual or functional)

The Basic MotivationThe Basic Motivation

Scientific explanation of category-specific deficits center Scientific explanation of category-specific deficits center around the basic question of around the basic question of Q1: How is conceptual Q1: How is conceptual knowledge organized?knowledge organized?

Cognitive Neuropsychology attempts to answer Q1 by Cognitive Neuropsychology attempts to answer Q1 by examining cases of individuals who seem disproportionately examining cases of individuals who seem disproportionately impaired at naming, defining, and/or characterizing impaired at naming, defining, and/or characterizing members of a given category, and do not exhibit similar members of a given category, and do not exhibit similar deficits in other categories. (e.g. S can’t name any x’s that deficits in other categories. (e.g. S can’t name any x’s that are animals, but can name all other x’s of category <living are animals, but can name all other x’s of category <living things>)things>)

If cognitive scientists can accurately predict the cause and If cognitive scientists can accurately predict the cause and nature of cases of category-specific impairments, then a nature of cases of category-specific impairments, then a theoretical backdrop for a cognitive theory of conceptual theoretical backdrop for a cognitive theory of conceptual knowledge could emergeknowledge could emerge

Methodology of this presentationMethodology of this presentation

1.1. Give brief summary and history of Give brief summary and history of category-specific deficitscategory-specific deficits

2.2. Discuss two competing theories of Discuss two competing theories of category-specific deficits category-specific deficits (Sensory/Functional Theory v. Domain-(Sensory/Functional Theory v. Domain-Specific Theory)Specific Theory)

3.3. Discuss these in terms of particular cases Discuss these in terms of particular cases which purported to support themwhich purported to support them

4.4. Discuss explanatory inconsistencies for Discuss explanatory inconsistencies for both of the theories, discuss soundness both of the theories, discuss soundness of their respective presumptionsof their respective presumptions

History of the ConditionHistory of the Condition First clear exampleFirst clear example: Warrington & Shalice (1984) : Warrington & Shalice (1984)

describe 4 patients recovering from herpes simplex describe 4 patients recovering from herpes simplex encephalitis that appear disproportionately impaired at encephalitis that appear disproportionately impaired at both comprehension and naming of living things v. both comprehension and naming of living things v. nonliving thingsnonliving things

W & S (1984) also observed case of brain-damaged W & S (1984) also observed case of brain-damaged individual w/reverse dissociation (i.e. nonliving things were individual w/reverse dissociation (i.e. nonliving things were problematic, but living things were not)problematic, but living things were not)

W & S inferred from these 5 instances that selective brain W & S inferred from these 5 instances that selective brain damage could result in category-specific semantic deficitsdamage could result in category-specific semantic deficits

Thus, a study of the nature of category-specific semantic Thus, a study of the nature of category-specific semantic deficits would prove fruitful for the study of the structure of deficits would prove fruitful for the study of the structure of semantic knowledge in normal subjectssemantic knowledge in normal subjects

History of the Condition (con’t)History of the Condition (con’t)

All 4 cases showed disproportionate difficulty for living vs. All 4 cases showed disproportionate difficulty for living vs. nonliving thingsnonliving things

J.B.R. reported as J.B.R. reported as unableunable to recognize/name to recognize/name 2/48 living 2/48 living thingsthings (animals or plants) but (animals or plants) but couldcould describe/named describe/named 45/48 45/48 nonliving thingsnonliving things

S.B.Y. identified 0/48 living things but identified 36/48 S.B.Y. identified 0/48 living things but identified 36/48 nonliving thingsnonliving things

Subsequently, confirmation of dissociation b/w living v. Subsequently, confirmation of dissociation b/w living v. nonliving things obtained in many other studies of brain-nonliving things obtained in many other studies of brain-damaged subjects (variance in etiology; herpes simplex damaged subjects (variance in etiology; herpes simplex encephalitis, trauma, cerebro-vascular accident, encephalitis, trauma, cerebro-vascular accident, neurosurgery)neurosurgery)

Reverse dissociation also confirmed: impaired performance Reverse dissociation also confirmed: impaired performance nonliving objects v. spared ability with living thingsnonliving objects v. spared ability with living things

Basic Methodological Assumptions/PracticesBasic Methodological Assumptions/Practices

Picture-naming taskPicture-naming task necessarily involves activation of necessarily involves activation of semantic information about a particular object (usual method semantic information about a particular object (usual method is to use Snodgrass and Vanderwart picture set)is to use Snodgrass and Vanderwart picture set)

Comprehension testsComprehension tests: administered after picture-naming : administered after picture-naming task, these tests involve the individual’s ability to distinguish task, these tests involve the individual’s ability to distinguish features of objects; are meant to demonstrate either:features of objects; are meant to demonstrate either:

(a)(a) that the individual’s that the individual’s problem results from the inability to problem results from the inability to recognize the problem-objectrecognize the problem-object, in which case the relevant , in which case the relevant system is system is not at allnot at all presentedpresented with the necessary features to with the necessary features to produce the desired output -OR-produce the desired output -OR-

(b)(b) That the individual’s That the individual’s problem results from an inability to problem results from an inability to properly extractproperly extract properties of the problem-object which are properties of the problem-object which are somewhere present in the system somewhere present in the system (the latter seems more likely, (the latter seems more likely, given the lack of instances in which a subject’s dissociation is given the lack of instances in which a subject’s dissociation is necessary; i.e. it is not the case that S cannot properly identify all necessary; i.e. it is not the case that S cannot properly identify all entities of category entities of category cc, it is that he cannot properly identify all , it is that he cannot properly identify all entities in category entities in category cc effectively, or consistently, or functionally) effectively, or consistently, or functionally)

Is the semantic system organized Is the semantic system organized categorically?categorically?

Hypothesis that the semantic system is categorically Hypothesis that the semantic system is categorically organized initially not seriously entertainedorganized initially not seriously entertained

Inconsistent findings for category hypothesis from initial Inconsistent findings for category hypothesis from initial cases usually manifest in that patterns of affected cases usually manifest in that patterns of affected semantic categories failed to correspond to definite semantic categories failed to correspond to definite categorical distinctionscategorical distinctions

Reasons for initial rejection:Reasons for initial rejection:1.1. If semantic system is categorically organized, then JBR’s If semantic system is categorically organized, then JBR’s

category-specific deficit should correspond to definite category-specific deficit should correspond to definite semantic categorical distinctions, like living v. nonlivingsemantic categorical distinctions, like living v. nonliving

2.2. JBR’s deficit is in animal & plant categories (living) AND JBR’s deficit is in animal & plant categories (living) AND food category (nonliving)food category (nonliving)

3.3. Thus, hypothesis that semantic system is categorically Thus, hypothesis that semantic system is categorically organized is violatedorganized is violated

Proposal of Sensory/Functional Theory of Category-specific Proposal of Sensory/Functional Theory of Category-specific deficitsdeficits

Refutation of hypothesis that semantic system is categorically Refutation of hypothesis that semantic system is categorically organized lead Warrington & Shalice (1984) to propose organized lead Warrington & Shalice (1984) to propose Sensory/Functional theorySensory/Functional theory

This theory says that JBR and SBY’s case can be explained by This theory says that JBR and SBY’s case can be explained by accounting for damage to visual semantic subsystem and/or accounting for damage to visual semantic subsystem and/or damage to functional semantic subsystemdamage to functional semantic subsystem

Visual semantic subsystemVisual semantic subsystem: damage to this area results in : damage to this area results in disproportionate deficit of living things and foods because the disproportionate deficit of living things and foods because the identification of both contingent on visual featuresidentification of both contingent on visual features

Functional semantic subsystemFunctional semantic subsystem: damage to this area results in : damage to this area results in disproportionate deficit of nonliving things because nonliving disproportionate deficit of nonliving things because nonliving things are distinguished based on utility or function. things are distinguished based on utility or function.

THUS, apparent categorical nature of semantic deficits doesn’t THUS, apparent categorical nature of semantic deficits doesn’t reflect categorical structure of semantic knowledge, but reflects reflect categorical structure of semantic knowledge, but reflects instead a more basic organizing principle of semantic system instead a more basic organizing principle of semantic system contingent on sensory and functional cues contingent on sensory and functional cues

Sensory/Functional TheorySensory/Functional Theory

PrinciplePrinciple

1.1. Non-categorical, Non-categorical, modality-specific modality-specific organizationorganization

2.2. Differential Differential attribution of living v. attribution of living v. nonliving thingsnonliving things

ExplanationExplanation1.1. Semantic system Semantic system

organized into modality-organized into modality-specific subsystems specific subsystems (visual/perceptual, (visual/perceptual, functional/associative)functional/associative)

2.2. Ability to recognize/name Ability to recognize/name living things contingent living things contingent on visual/perceptual info.; on visual/perceptual info.; non-living things non-living things contingent on contingent on functional/associative functional/associative info.info.

Case Study 1: Bert (Barry & McHattie)Case Study 1: Bert (Barry & McHattie)

Barry & McHattie case study supports Barry & McHattie case study supports Sensory/Functional Sensory/Functional TheoryTheory

Bert, age 74, had stroke which caused right visual field Bert, age 74, had stroke which caused right visual field defect, no problems with conversation, intellectually intact, defect, no problems with conversation, intellectually intact, preserved comprehensionpreserved comprehension

Complained of both word-finding difficulties and Complained of both word-finding difficulties and pronounced inability to name entities in the category of pronounced inability to name entities in the category of animalsanimals

Barry and McHattie wanted to explore possibility of Barry and McHattie wanted to explore possibility of category-specific anomia for animalscategory-specific anomia for animals

Initial testingInitial testing: appeared to have intact object recognition : appeared to have intact object recognition (verified by appropriate use of household items and by his (verified by appropriate use of household items and by his performance of a test which tested object recognition; performance of a test which tested object recognition; shown 3 different pictures, had to indicate by pointing shown 3 different pictures, had to indicate by pointing which of the three pictures had objects which contained which of the three pictures had objects which contained items with the same name, otherwise 2 things of same items with the same name, otherwise 2 things of same name but different physical appearances)name but different physical appearances)

Bert con’tBert con’t

Picture naming task: Bert presented with Picture naming task: Bert presented with 100 line drawings of Snodgrass and 100 line drawings of Snodgrass and Vanderwart testVanderwart test

Either produced correct name of the Either produced correct name of the picture, or indicated he couldn’t say it and picture, or indicated he couldn’t say it and would subsequently partake in some would subsequently partake in some degree of descriptiondegree of description

For instances in which Bert could not For instances in which Bert could not name it, he indicated too that he ‘knew name it, he indicated too that he ‘knew the thing’.the thing’.

Results of Picture NamingResults of Picture Naming

Success rateSuccess rate::

(a)(a) Animal naming=12%Animal naming=12%

(b)(b) Fruits/vegetables Fruits/vegetables naming=47%naming=47%

(c)(c) Musical instruments= Musical instruments= 50%50%

(d)(d) Tools=60%Tools=60%

(e)(e) Vehicles=67%Vehicles=67%

(f)(f) Articles of Articles of clothing=71%clothing=71%

(g)(g) Body-parts=100%Body-parts=100%

Worst at naming animals Worst at naming animals as compared to any other as compared to any other categorycategory

Data does not fit Data does not fit hypothesis that semantic hypothesis that semantic knowledge organized into knowledge organized into discrete categoriesdiscrete categories

Word familiarity, visual Word familiarity, visual complexity of pictures, and complexity of pictures, and age-of-acquisition did age-of-acquisition did effect Bert’s responses for effect Bert’s responses for the task (e.g. Bert was the task (e.g. Bert was better at naming familiar better at naming familiar items vs. non-familiar) items vs. non-familiar)

Possible Reasons for Bert’s DeficitPossible Reasons for Bert’s Deficit

ReasonsReasons

(a)(a) Inability to recognize Inability to recognize animalsanimals

(b)(b) Problematic integrity Problematic integrity of semantic of semantic representation of representation of animal, or problem animal, or problem with the utilization of with the utilization of those those representations representations which support proper which support proper namingnaming

ExplanationExplanation

(a)(a) refuted, Bert could refuted, Bert could point to appropriate point to appropriate animal in a picture of animal in a picture of two related animals two related animals when prompted by an when prompted by an animal nameanimal name

(b)(b) Possible, Possible, comprehension test comprehension test follows to seek out follows to seek out this possibilitythis possibility

Comprehension TestComprehension Test 4 questions for each of the 30 animals + 30 items 4 questions for each of the 30 animals + 30 items

presented to Bert:presented to Bert: One required ‘yes’ response about category of the item One required ‘yes’ response about category of the item

(e.g. Is a squirrel an animal?)(e.g. Is a squirrel an animal?) One contained false information about category of object One contained false information about category of object

(e.g. is a mushroom a musical instrument?)(e.g. is a mushroom a musical instrument?) One was a correct question about physical appearance of One was a correct question about physical appearance of

item of category (e.g. has a squirrel got a bushy tail?)item of category (e.g. has a squirrel got a bushy tail?) One was false question about physical appearance (e.g. has One was false question about physical appearance (e.g. has

a squirrel got wings?)a squirrel got wings?)

Results of Comprehension TestResults of Comprehension Test

Type of QuestionType of Question 1) Category Questions1) Category Questions 2) Physical Property 2) Physical Property

QuestionsQuestions

ResultsResults 1) 93.3% correct for 1) 93.3% correct for

category questionscategory questions 2) 76.7% correct for 2) 76.7% correct for

questions about questions about physical propertiesphysical properties

**Thus, Bert’s inability to name and recognize members of the animal category is because of a malfunctioning visual semantic subsystem, according to Sensory/Functional Theory

*significant difference b/w 1 and 2, thus his category-specific problem is a reflection of a failure to account for physical properties which distinguish members of animal category from members of other categories

Problems for the Sensory/Functional TheoryProblems for the Sensory/Functional Theory

Because this theory assumes that ability to recognize all Because this theory assumes that ability to recognize all living things differentially contingent on info internal to the living things differentially contingent on info internal to the same visual/perceptual subsystem, prediction is that a same visual/perceptual subsystem, prediction is that a dissociation will not be observed within same category ‘living dissociation will not be observed within same category ‘living things’. things’.

CONTRARY to this is the report of individuals with CONTRARY to this is the report of individuals with disproportionate deficits for ‘fruits/vegetables’ v. ‘animals’disproportionate deficits for ‘fruits/vegetables’ v. ‘animals’

Predicts patients will present w/disproportionate deficits for Predicts patients will present w/disproportionate deficits for type of info upon which successful recognition of impaired type of info upon which successful recognition of impaired category is assumed to depend on. Early reports supported category is assumed to depend on. Early reports supported this, but data has been criticized on methodological grounds this, but data has been criticized on methodological grounds (pictures unmatched for word frequency et cetera)(pictures unmatched for word frequency et cetera)

Predicts association b/w disproportionate deficit for type of Predicts association b/w disproportionate deficit for type of knowledge & disproportionate deficit for category of objects knowledge & disproportionate deficit for category of objects that depends on that knowledge. that depends on that knowledge.

CONTRARY to this: patients reported w/ disproportional CONTRARY to this: patients reported w/ disproportional deficit in functional/associative knowledge but no associated deficit in functional/associative knowledge but no associated disproportionate deficit for living things v. non-living thingsdisproportionate deficit for living things v. non-living things

Domain-Specific HypothesisDomain-Specific Hypothesis

Central assumptionCentral assumption: evolutionary pressures : evolutionary pressures resulted in specialized neural circuits dedicated resulted in specialized neural circuits dedicated to processing (both conceptually and to processing (both conceptually and perceptually) distinct categories of objects. perceptually) distinct categories of objects. Instantiates the notion that semantic system Instantiates the notion that semantic system may be organized categorically. (Warrington, may be organized categorically. (Warrington, 1981)1981)

Provides independent specifications for how we Provides independent specifications for how we can characterize a conceptual category; can characterize a conceptual category; restricted only to categories that were restricted only to categories that were advantageous with respect to survival and advantageous with respect to survival and reproductive advantagesreproductive advantages

Domain-Specific Hypothesis con’tDomain-Specific Hypothesis con’t

PredictionsPredictions: :

1.1. If there are distinct neural systems dedicated to categories of If there are distinct neural systems dedicated to categories of ‘animals’, ‘fruits/vegetables’, and possibly ‘tools’, then it’s ‘animals’, ‘fruits/vegetables’, and possibly ‘tools’, then it’s impossible for function of one system, if damaged, to be impossible for function of one system, if damaged, to be recovered by other systems (i.e. predicts poor-recovery of recovered by other systems (i.e. predicts poor-recovery of impaired performanceimpaired performance

2.2. No necessary correspondence b/w deficit for knowledge of No necessary correspondence b/w deficit for knowledge of modality x and conceptual deficit for category of objectsmodality x and conceptual deficit for category of objects

3.3. Patients might present category-specific visual agnosia. This Patients might present category-specific visual agnosia. This follows from assumption that perceptual stages of object follows from assumption that perceptual stages of object recognition are possibly functionally organized according to recognition are possibly functionally organized according to domain-specific restrictions. (supported by observation of domain-specific restrictions. (supported by observation of subjects with equal deficits to visual and functional knowledge subjects with equal deficits to visual and functional knowledge of living things, but visual agnosia for living things v. non-of living things, but visual agnosia for living things v. non-living things)living things)

Case 2: Patient EW (Caramazza and Shelton, 1998)Case 2: Patient EW (Caramazza and Shelton, 1998)

This case is purported to support the This case is purported to support the Domain-Specific Domain-Specific HypothesisHypothesis (Caramazza and Shelton, 1998) (Caramazza and Shelton, 1998)

Patient EW: selective deficit for category of animals, Patient EW: selective deficit for category of animals, equally impaired for visual and functional attributes of equally impaired for visual and functional attributes of members of animal category v. other living things and members of animal category v. other living things and artifacts artifacts

E.W. tested via Picture Naming, Sound Identification, E.W. tested via Picture Naming, Sound Identification, Object decision, Parts decision, Visual processing, and Object decision, Parts decision, Visual processing, and Central-Attribute judgmentsCentral-Attribute judgments

Picture NamingPicture Naming

Snodgrass & Vanderwart picture set, matched for Snodgrass & Vanderwart picture set, matched for familiarity and frequencyfamiliarity and frequency

EW disproportionately impaired at naming animals EW disproportionately impaired at naming animals (55%) v. non-animals (82%). Controls were 100% at (55%) v. non-animals (82%). Controls were 100% at naming animals and 98% for non-animalsnaming animals and 98% for non-animals

EW’s performance both quantitatively and qualitatively EW’s performance both quantitatively and qualitatively different for animals v. non-animals. Animals, EW different for animals v. non-animals. Animals, EW either named picture incorrectly or did not recognize either named picture incorrectly or did not recognize picture; for non-animals, EW recognized the picture but picture; for non-animals, EW recognized the picture but couldn’t retrieve namecouldn’t retrieve name

EW’s deficit did not extend to other living things like EW’s deficit did not extend to other living things like the category ‘fruit/vegetables’ (performed very well in the category ‘fruit/vegetables’ (performed very well in this category)this category)

Sound IdentificationSound Identification

Task presented E.W. with 32 characteristic Task presented E.W. with 32 characteristic sounds of animals and 32 non-animal sounds sounds of animals and 32 non-animal sounds

E.W. impaired at naming animals v. non-animals E.W. impaired at naming animals v. non-animals based on characteristic sound (25% correct v. based on characteristic sound (25% correct v. 63%)63%)

This indicates that naming impairment is not This indicates that naming impairment is not restricted to one sensory systemrestricted to one sensory system

Object DecisionObject Decision

Asked to decide ‘yes’ or ‘no’ whether depicted Asked to decide ‘yes’ or ‘no’ whether depicted object was real.object was real.

Performance on this task is interpreted as Performance on this task is interpreted as reflecting integrity of visual/structural description reflecting integrity of visual/structural description system (this was system purported to be one of system (this was system purported to be one of the causes of Bert’s naming problems)the causes of Bert’s naming problems)

Significantly below normal range for Significantly below normal range for differentiating b/w real from unreal animals (60% differentiating b/w real from unreal animals (60% correct, controls were 90%)correct, controls were 90%)

Within normal range for distinguishing real from Within normal range for distinguishing real from unreal non-animals (92% correct, controls were unreal non-animals (92% correct, controls were 84%)84%)

Parts Decision TaskParts Decision Task

EW to decide which of two heads went EW to decide which of two heads went with headless bodywith headless body

Severely impaired on this task for animals Severely impaired on this task for animals (60%, controls were 100%) (60%, controls were 100%)

Normal range for artifacts (97%, controls Normal range for artifacts (97%, controls were 97%were 97%

Indicates that EW doesn’t have deficit for Indicates that EW doesn’t have deficit for visual processing for complex stimulivisual processing for complex stimuli

Suggests her impairment for objects Suggests her impairment for objects reality decision for animals is categorically reality decision for animals is categorically basedbased

Central-Attribute JudgmentsCentral-Attribute Judgments

EW asked to decide if a given attribute was true of a given EW asked to decide if a given attribute was true of a given item. This tests ability to distinguish properties/features of item. This tests ability to distinguish properties/features of an objectan object

Severely impaired for attributes pertaining to animals (65%, Severely impaired for attributes pertaining to animals (65%, controls were 85-100%)controls were 85-100%)

Normal range for attributes pertaining to non-animals (95%, Normal range for attributes pertaining to non-animals (95%, controls were 85-100%)controls were 85-100%)

Equivalently impaired for visual/perceptual and Equivalently impaired for visual/perceptual and functional/associative knowledge of living things (65% for functional/associative knowledge of living things (65% for both) both)

Normal range for both types of knowledge for non-animalsNormal range for both types of knowledge for non-animals Thus, EW’s performance on central-attribute questions Thus, EW’s performance on central-attribute questions

implies that her deficit is not restricted to productionimplies that her deficit is not restricted to production

Conclusions and Speculations of EW CaseConclusions and Speculations of EW Case

Results summarized by Caramazza & Shelton:Results summarized by Caramazza & Shelton:

1.1. EW has category-specific deficit restricted to category of EW has category-specific deficit restricted to category of animate objects (this persisted under strict control of animate objects (this persisted under strict control of nuisance factors like familiarity, visual complexity, nuisance factors like familiarity, visual complexity, frequency, or combination of them)frequency, or combination of them)

2.2. Category-specific deficit manifests in visually and Category-specific deficit manifests in visually and auditorily recognizing animate objectsauditorily recognizing animate objects

3.3. Category-specific deficit in language comprehension; Category-specific deficit in language comprehension; manifested in poor performance w/ statements about manifested in poor performance w/ statements about animate objects v. normal limits w/statements about animate objects v. normal limits w/statements about other living things and artificatsother living things and artificats

Domain Specific Organization of Conceptual Knowledge Domain Specific Organization of Conceptual Knowledge and Evolutionary Adaptationand Evolutionary Adaptation

Fact that the categories animals, fruits/vegetables, and Fact that the categories animals, fruits/vegetables, and artifacts can be independently impaired suggests that it is artifacts can be independently impaired suggests that it is the case that ONLY these three categories form basis for the case that ONLY these three categories form basis for conceptual organization of conceptual knowledge conceptual organization of conceptual knowledge

This assumption requires independent empirical This assumption requires independent empirical justification; recourse to evolutionary adaptation could justification; recourse to evolutionary adaptation could provide such justificationprovide such justification

Recognition of animal category would imply ability to Recognition of animal category would imply ability to respond quickly to all types of animals, including predators. respond quickly to all types of animals, including predators. Physiological evidence: we can detect movement of living Physiological evidence: we can detect movement of living organisms faster than movement of non-living things, we organisms faster than movement of non-living things, we require less information require less information

Evolutionary adaptations for recognition of animals and Evolutionary adaptations for recognition of animals and plant life provides skeletal neural structures which would plant life provides skeletal neural structures which would organize perceptual, conceptual, and linguistic knowledge organize perceptual, conceptual, and linguistic knowledge modern humans have of these categoriesmodern humans have of these categories

Domain Specific Organization of Conceptual Domain Specific Organization of Conceptual Knowledge and Evolutionary Adaptation con’tKnowledge and Evolutionary Adaptation con’t

ImplicationImplication: only true : only true category-specific deficits category-specific deficits are those which involve are those which involve categories of animal, plant-categories of animal, plant-life, and possibly artifactslife, and possibly artifacts

ImplicationImplication: supposition : supposition that specialized neural that specialized neural mechanisms are more mechanisms are more likely to be selectively likely to be selectively damaged implies that damaged implies that frequency of category-frequency of category-specific deficits for living specific deficits for living things should be higher things should be higher than non-living things. than non-living things.

More specific categories More specific categories like tools would not like tools would not constitute a category-constitute a category-specific deficit, because specific deficit, because the category of tools does the category of tools does not serve the function of not serve the function of organizing semantic organizing semantic knowledge into categoriesknowledge into categories

This 2This 2ndnd implication is implication is supported in that most supported in that most cases of category-specific cases of category-specific deficits are manifested in deficits are manifested in animal or plant categories animal or plant categories (aka, fruits/vegetables)(aka, fruits/vegetables)

ConclusionsConclusions Given that, as it stands now, there is a higher Given that, as it stands now, there is a higher

degree of supporting evidence for domain-specific degree of supporting evidence for domain-specific theory compared w/sensory-functional theory, theory compared w/sensory-functional theory, domain-specific theory explains category-specific domain-specific theory explains category-specific deficits better deficits better

Also, much of the evidence for sensory/functional Also, much of the evidence for sensory/functional theory was thrown out due to fact that theory was thrown out due to fact that uncontrolled stimulus factors like familiarity could uncontrolled stimulus factors like familiarity could account for apparent deficitaccount for apparent deficit

When these factors were controlled, many of the When these factors were controlled, many of the early cases supporting sensory/functional theory early cases supporting sensory/functional theory were shown to have been partially a function of were shown to have been partially a function of uncontrolled stimulus factorsuncontrolled stimulus factors

Works CitedWorks Cited Caramazza, A., & Mahon, B. (2003). The Organization of Caramazza, A., & Mahon, B. (2003). The Organization of

Conceptual Knowledge: the Evidence from Category-Conceptual Knowledge: the Evidence from Category-Specific Semantic Deficits. Specific Semantic Deficits. Trends in Cognitive SciencesTrends in Cognitive Sciences, 7: , 7: 8, pp. 354-3618, pp. 354-361

Caramazza A., & Shelton, J. (1998). Domain-Specific Caramazza A., & Shelton, J. (1998). Domain-Specific Knowledge Systems in the Brain: The Animate-Inanimate Knowledge Systems in the Brain: The Animate-Inanimate Distinction. Distinction. Journal of Cognitive NeuroscienceJournal of Cognitive Neuroscience, 10:1, pp. 1-, 10:1, pp. 1-3434

Lombardi, L. & Sartori, G. (2004). Semantic Relevance and Lombardi, L. & Sartori, G. (2004). Semantic Relevance and Semantic Disorders. Semantic Disorders. Journal of Cognitive NeuroscienceJournal of Cognitive Neuroscience, , 16:3, pp. 439-45216:3, pp. 439-452

Warrington, E.K., & Shalice, T. (1984). Category-Specific Warrington, E.K., & Shalice, T. (1984). Category-Specific Semantic Impairments. Semantic Impairments. BrainBrain, 107, 829-854, 107, 829-854