Representation and Organization of Knowledge in Memory

REPRESENTATIONand ORGANIZATION of
KNOWLEDGEin MEMORY:
Concepts,Categories,NetworksandSchemas

REPRESENTATIONand ORGANIZATIONof KNOWLEDGEinMEMORY:
Concepts, Categories, NetworksandSchemas
1. How are representations of words and symbols organized in the
mind?
2. How do we represent other forms of knowledge in the mind?
3. How does declarative knowledge interact with procedural
knowledge?
INTRODUCTION

ORGANIZATION
OF
DECLARATIVE KNOWLEDGE

ORGANIZATIONOF DECLARATIVEKNOWLEDGE
-CONCEPT –
thefundamentalunitofsymbolicknowledge
(knowledgeofcorrespondencebetween symbolsand
their meaning forexample, thatsymbol“3”means
three),anidea aboutsomething thatprovidesa
means ofunderstandingtheworld.
-CATEGORY-
is agroupofitemsintowhich different
objects orconceptscanbeplacedthat
belong togetherbecausetheysharesome
commonfeatures,orbecausetheyare
similar toacertainprototype.

Concepts and Categories
Concepts and categories can bedivided in various ways:
NATURAL CATEGORIES
ARTIFACT CATEGORIES
are groupings that occur naturallyinthe world like
birds or tree.
are groupings that are designed or inventedbyhumansto serve
particular purposes or functions.
NaturalandArtifact Categoriesarerelatively stableandpeopletendtoagree
oncriteriaformembership.

On the contrary..
-CONCEPTS-
arenotalwaysstable butcan change.
Theyaredescribed notin wordsbut
ratherin phrases.
theyalsoappearto havea basiclevel
(sometimes termed asanaturallevel) of
specificity,a level within ahierarchythat
is preferredtootherlevels.

In general, thebasic levelis neitherthemost
abstract nor the most specific. This basic
level can be manipulatedby contextor
expertise.

Thebasic level is the one that most peoplefind to be maximally distinctive. By
means of training, the basic level can be shifted to a more subordinate level.
For example, the more a personlearns about cars, the more he orshe is likely to
make elaborate distinction among cars.
Research suggests that the difference between experts and novices are not due to
qualitative mechanisms but rather quantitative differences in processing efficacy.

So, how do we decidewhat objects to put
into a category?

-FEATURE-BASEDCATEGORIES
-PROTOTYPE THEORY
-THEORY BASED VIEW OF CATEGORIZATION
-SEMANTIC-NETWORK MODELS
-SCHEMATIC REPRESENTATIONS

FEATURE-BASEDCATEGORIES:
A DEFINING VIEW
the classicview of categoriesdisassemblesa conceptintoaset offeatural
components.All thosefeaturesarethen necessary(andsufficient) to
definethe category.This meansthateach featureis anessential element
ofthe category.Together,thefeaturesuniquelydefinethe category;they
aredefining features.
For a thing to be anX, it must have that feature. Otherwise it is not an “X”.

BACHELOR
MALE
UNMARRIED
ADULT

WIFE
FEMALE
MARRIED
ADULT

TheProblem:
1. Somecategories do not readily lend themselves to featural
analysis.
2. A violation ofthose defining features does not seem to changethe
category we useto define them.

In sum, the feature-basedtheory has some
attractive features, but it does not give a
complete account of categories.

PROTOTYPETHEORY:
A CHARACTERISTICVIEW
grouping thingstogethernotbytheir defining featuresratherbytheir
similaritytoanaveragedmodel ofthe category.
PROTOTYPE
is anabstract average of all the
objects the category we have
encounteredbefore
CHARACTERISTICFEATURE
describe (characterizeor typify) prototype but are
not necessary for it.

So what exactlyis a characteristicfeature?
whereasa defining featureis sharedbyevery single object in acategory,a
characteristicfeatureneed nottobeInstead,manyor mostinstancespossess
each characterfeature..

Psychologistsdifferentiatetwokindsofcategories:
Classicalconcepts andFuzzyConcepts.
CLASSICAL CONCEPTS FUZZYCONCEPTS
-Canbe readilydefined through
defining features
-May be built on defining features
-Cannotbe so easily defined
-Built aroundprototypes

Real-World Examples: UsingExemplars
SomePsychologistssuggeststhatinsteadof using asingle
abstractprototypeforcategorizingaconcept, weusemultiple,
specific exemplars.
EXEMPLARS aretypicalrepresentativesofa category
In particular,categoriesareset upbycreating arule andthenbystoringexamplesasexemplars.
Objectsarethencomparedtothe exemplarstodecide whetherornottheybelong in the category
the exemplarsrepresent.

ASYNTHESIS:
COMBINING FEATURE-BASEDandPROTOTYPETHEORIIES
A full theoryof categorization can combine both defining and characteristic features, so that each
category has both prototype and aCORE.
CORE refersto the defining features something must haveto be considered anexample of
category.
Theprototype encompasses thecharacteristic features that tend to betypical of an examplebut that are not
necessary for being considered as an example.
Thecore requiresthat someone labeled as a robber bea person who takes things from otherswithout
permission. Theprototype, however, tends to identify particular people as more likelyto be robbers.

“ROBBER
”

A departure from feature-based,prototype-based, and
exemplar-based views of meaningis a THEORY BASED
VIEW of meaningalso sometimes called an EXPLANATION-
BASED VIEW.

HOW DO PEOPLEUSE THEIR THEORIES
FOR CATEGORIZATION?

A THEORY BASED VIEW OFMEANING hold that people understand and
categorize concepts in terms of implicittheories, or generalideasthey have
regarding those concepts.
For example, what makes a GOOD SPORT?

In thePROTOTYPEVIEW,
youwouldtryto findcharacteristicfeaturesofa good
sport.
In theCOMPONENTIALVIEW,youwouldtrytoisolate
featuresof agoodsport.
In theEXAMPLARVIEW,youmight trytofindsome
goodexamplesyouhaveknownin yourlife.

In thetheory-based view, you would use your
experience to construct an explanationfor what
makes someone a good sport.

SO what does it means to bea GOODSPORT in a theory-based
view?
A good sport is someone who, when he or shewins, is gracious in victory and dos
not mocklosers orotherwise make them feel bad about losing. It is also someone
who, when heorsheloses, loses graciously and does not blame the winner, the
referee, or find excuses. Rather, heorshe takes the defeat in stride, congratulates
the winner, and then moves on.

FINDINGTHE “ESSENCE”OF THINGS

SEMANTIC-NETWORK MODELS
Semantic Network Models suggests that knowledge is represented in our
minds in the form of concepts that are connected with each other in a web-
like form

Collins and Quillan’s NetworkModels
Knowledgeis representedin termsofhierarchalsemanticnetwork.
A SEMANTIC NETWORK is a web of elements of meaning (nodes) that are
connected with each otherthrough links.

ORGANIZED KNOWLEDGE representation takes the form of a hierarchal tree diagram.
Theelements are called nodes they are typically concepts.
Theconnections between the nodes are labeled relationships. Theymay indicate
category membership, attributes, orsome other semantic relationship. Thus a network
provides a means of organizing concepts.

INHERITANCE
This concept implies that lower-level
items inherit the properties of higher-
level items.
Whateverwasknownaboutitems athigher
levels in ahierarchywasapplied toall items at
lower levels in thehierarchy

COMPARISON OF SEMANTIC FEATURES
Knowledge is organized based on a comparison of semantic features, rather
than on a strict hierarchy of concepts

Representation and Organization of Knowledge in Memory

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