Introduction to Categorization Theory

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Introduction to Categorization Theory

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Introduction to Categorization Theory(Goldstein Ch 9: Knowledge)

Psychology 355: Cognitive PsychologyInstructor: John Miyamoto05/10/2018: Lecture 07-4

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OutlineFinish: Eyewitness memory

Introduction to categorization theory (Goldstein's chapter 9 is named "Knowledge)Categorization – what is it?How are objects placed into categories?

The definitional theory of categorization

Problems with the definitional theory of categorization

Prototype theory of categorizationExemplar theory of categorization

Psych 355, Miyamoto, Spr '18


Lecture probably ends here

Line Ups Versus Show Ups


Psych 355, Miyamoto, Spr '18

3Lineups versus Show-Ups – What Are They?



: Police show only one person to a witness, often somebody who was caught near the scene of the crime. Question: "Is he the man you saw?"Classic lineup: Police show 7 people to the witness:

Question: "Do you see the perpetrator in the line up?"Improved showup

= sequential showup: Police tell the witness, "We're going to show you a series of men (of unstated length).

Stop me when you see the perpetrator."

Contrary to most people's expectations, show ups are more accurate than line ups. Why are showups more accurate than lineups?

Why Lineups & Showups Differ as Cognitive Tasks


Psych 355, Miyamoto, Spr '18

4Cognitive Differences Between Lineups and Showups



: Witness asks himself/herself: "Did I see this person do the crime?"Classic lineup:Witness assumes that the perpetrator is in the lineup.Witness asks himself/herself:

"Which of these men looks the most like the person that I saw?"

Sequential presentation = sequential showup

(Goldstein refers to this a sequential presentation)With each person, the witness

asks himself/herself: "Am I sure that this is the person who I saw do the crime?"Lindsey & Wells (1985) found that the sequential showup greatly reduced

false id when the perpetrator was not present (43% vs 17%)Sequential showups slightly reduced the rate of true id when perpetrator is present.

Recommendations for Improving Eyewitness Memory




Psych 355, Miyamoto, Spr '18

5Recommendations for Improving Eyewitness Memory Use a sequential showup

(Goldstein would call it a sequential presentation). In a showup, use non-suspects who are similar to a suspect.

Inform witness that the perpetrator may not be in a showup.

Administrator of showup should not know who is the suspect.

Get confidence rating immediately after the initial identification.

Avoid giving feedback to the witness after the lineupUse cognitive interview techniques; do not prompt the witness with leading questions.

See Wikipedia article on cognitive interview techniques:

Outline of Categorization Topic


End of the Memory Topic

The slides that follow this slide pertain to Goldstein’s Chapter 9 (Knowledge; I refer to it as the categorization topic). Chapter 9 will not be on Midterm 2. Psych 355, Miyamoto, Spr '18



Outline of Categorization TopicConcepts, categorization, and knowledge

Categorization – what is it?How are objects placed into categories?The definitional theory of categorizationProblems with the definitional theory of categorization

Prototype theory of categorization

Exemplar theory of


Psych 355, Miyamoto, Spr '18


Categorization – Examples


Psych 355, Miyamoto, Spr '18

8Categorization – ExamplesCategorize objects in the physical world. E.g., tables, chairs, cars, dogs, cats, trees, water, etc.

Categorize types of people.

E.g., policemen, teachers, students, politician, etc.

E.g., friend, enemy, helpful, inconsiderate, smart, talkative, etc.E.g., white, black, asian, ...., catholic, muslim, hindu, ...., Abstract categories."___ is a crime", e.g., theft is a crime; complaining is not a crime."___ is a relative of mine." (Kinship is an abstraction.)"credit" in the financial sense is an abstraction.

Inferences with Categorizations


Inferences with Categories

Example of Reasoning

with Categories

Type of Inference

I see a dog and say,

"That's a mammal/dog/collie."

Categorize an object

(put it into a category)

A friend tells me, "I have a collie



I think to myself, "I hope she doesn't mind dog hair on her clothes."

Draw an inference from a categorization to other

properties of

the object.

A friend tells me that

fluorescent light can wreck a cd that contains data

. I think to myself, I wonder if the same thing is true of



Draw an inference from a property of one category to a possible property of another category.

Psych 355, Miyamoto

, Spr '18


Categories Imply a Lot of Other Information – Cat Example


Psych 355, Miyamoto, Spr '18

10Knowing the Category Provides a Lot of Information

Definition of Categorization


Psych 355, Miyamoto, Spr '18

11Categorization – What is it?Goldstein book: Categorization "is the process by which things are placed into groups called categories."


is an incomplete definition. Below is a better definition.

The psychology of categorization has to do with:how we assign objects or events to categories;the structure of knowledge that we use to organize our knowledge

of categories (category structure);the inferences that we draw when we

learn that an object or event belongs to a category;how we learn new

categories (Children learn new categories frequently

; adults learn new categories from time to time)These are all examples of semantic knowledge.

Distinction Btwn Concepts & Categories


Psych 355, Miyamoto, Spr '18

12The word "concept" emphasizes knowledge of relationships between concepts.

E.g., the concept of a cat includes knowledge of its biology, appearance, behavior, its relation to human life styles, etc.


mokita (Kivila

language) is “truth we all know but agree not to talk about

” (Wikipedia)

Categories and Concepts

The word "category" emphasizes the set of all things that are joined together under a common label.

E.g., every cat is a member of the category "cat"; every dog and every cat is a



the category "carnivore."

Relationship between Knowledge and Categories


Categorization and KnowledgeGoldstein calls

the chapter topic “Knowledge” – why?This is a hypothesis – not a fact.IMO: The structure of categories and the structure of concepts are related to the structure of knowledge, but none is identicalto any of the others.



, Miyamoto, Spr '18



Definitional Approach to Category Membership


Psych 355, Miyamoto, Spr '18

14Definitional Approach to Category Membership

Originated with Aristotle. According to the definitional approach, category membership is determined by


a list of necessary and sufficient features.Example: Definition of a tea cup.Concrete object

ConcaveCan hold liquids

Has a handleCan be used to drink hot liquids

Properties 4 and 5 are debatable. Chinese tea cups. Lacquer cups. If you omit

4 and 5, then there are many objects (bowls) that satisfy 1 - 3.

Problems with the Definitional Approach


Psych 355, Miyamoto, Spr '18

15What Do These "Chairs" All Have in Common?Maybe there is nothing that ALL chairs have in common, .....


they all share

a family resemblance.

Problems with the Definitional Approach to Categorization


Psych 355, Miyamoto, Spr '18

16Problems with the Definitional ApproachHow do we discover the definitions? For many categories



is doubtful that necessary and sufficient features exist.Example: If we call someone "friendly,"

what are necessary and sufficient features for calling someone friendly?

The definitional approach does not explain important aspects of human categorization.

E.g., it does not explain typicality effects in categorization response time.

See the Rosch color priming study to be described later. E.g., it does not explain typicality effects in semantic memory experiments (Goldstein calls this the "sentence verification technique").

Prototype Theory of Categorization


Prototype Theory of CategorizationCognitive psychologists were dissatisfied with the definitional approach to representing cognitive categories.

Eleanor Rosch: Categories are organized around a category prototype. Category prototype represents typical features of category members. Family resemblances. Next

: Digression regarding family resemblances

Psych 355, Miyamoto

, Spr '1817

Family Resemblance Idea - Background


Psych 355, Miyamoto, Spr '18

18Family Resemblance Idea - BackgroundA "family resemblance"

photograph –


in late 19th & early 20th century. Take multiple exposure photo

of all family members. Only the common features are retained.

The photo looks like everyone in the family, but is not any on

e person.

Continuation of Present Slide with Composite Image

Images downloaded from:



Psych 355, Miyamoto, Spr '18

19Family Resemblance Idea - BackgroundA "family resemblance"

photograph –


in late 19th & early 20th century. Take multiple exposure photo

of all family members. Only the common features are retained.

The photo looks like everyone in the family, but is not any on

e person.Ludwig Wittgenstein –

early 20th century philosopher. Proposed that the structure of a

concept is like a family resemblance photo.

Family Resemblance in Concept Theory

Images downloaded from:


Paul Wittgenstein

Concert pianist

Lost right arm

in WW I


Psych 355, Miyamoto,

Spr '1820

Thursday, 10 May, 2018

: The Lecture Ended Here


Psych 355, Miyamoto, Spr '18

21Family Resemblance & ConceptsFamous example: Wittgenstein says that there are no necessary and sufficient conditions for something to be a "game", but there is a family resemblance among games.

Playing checkers or bridge; playing football; skipping rope;


play acting as if, e.g., having a tea party; trash talking Similarly, there

are no necessary& sufficient conditions for something

to be a chair, but there is a familyresemblance among chairs.

Return to Slide Showing the Prototype Theory of Categorization


Prototype Theory of Categorization

Eleanor Rosch proposed:cognitive representations of categories are like family resemblances.

categories have prototypes

category structure is created by the relationship between category members

and the category prototype. Prototypes (mental representation

of a concept) are like family resemblance photographs – they retain

the typical characteristics of many particular examples.

Psych 355, Miyamoto, Spr '1822

Examples of Birds & the Prototypical Bird Image

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