Category Structure Psychology 355: Cognitive Psychology Instructor: John Miyamoto 05/20 /2015: Lecture 08-2 This Powerpoint presentation may contain macros

Category Structure

Psychology 355: Cognitive Psychology

Instructor: John Miyamoto

05/20/2015: Lecture 08-2

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Outline

• Basic level of categorization.

• Network models of category structure.Connectionist models.

• The neural representation of category information.

Psych 355, Miyamoto, Spr '15 2Why Category Structure Is Important for Cog Psych Theory?

very brief

Assumption: Human perception, memory, language, and reasoning

are based on the ability to create, store, retrieve and manipulate a

variety of mental representations.

Representational Hypotheses

Cognitive Theory = Plus

Processing Hypotheses

• Category structure is a major part of the representational hypothesis

for cognitive theory.o E.g., What is the “semantic code” in which LTM’s are stored? o E.g., What is the representation of ideas when making a decision?

Psych 355, Miyamoto, Spr '15 3

Why Category Structure Is Important for Cognitive Psych

Mental Representations & Their Uses

Mental Representations and Their Uses

• Propositional representations

• Propositional networks

• Visuospatial representations (images; diagrams)

-----------------------------------------------------------

• Language comprehension. Language production. Conversation.

• Shared representations, e.g., category systems.

• Inference, decision, choice, & action

• Problem solving. Reasoning in general.

• Automatic pattern recognition.

Psych 355, Miyamoto, Spr '15 4Cat Image with Associated Properties - Reminder that We Are Discussing a Category Representation.

5Psych 355, Miyamoto, Spr '15

Knowing the Category Provides a Lot of Information

Is There a Basic Level of Categorization?


Is There a Basic Level in Categorization?

• Categories can often be arranged from higher-level superordinate

categories (more inclusive) to lower-level subordinate categories

(less inclusive; more specific).

• Eleanor Rosch asked: Is there a basic level of categorization at

which we habitually categorize the objects in our experience?

Basic Level Is Highest Level In Which Objects Share Many Features


What Defines the Basic Level of Categorization?

Hypothesis: The basic level is the highest level at which category members share many features within the category while also being very different from objects in other categories at the same level.

Two Factors that Determine the Basic Level:o Within a basic level category, objects share many features with each other.o Between different categories at the basic level, objects are very different

from each other.

Information Gain at Different Levels of Categorization

Information Provided by Categorizations at Different Levels


• If you categorize something at the superordinate level, e.g., "furniture," instead

of at the basic level, e.g., "table," you lose a lot of information about the object.

Concrete Example with Images of a Bull Do and a Pickup Truck

• If you categorize something at a subordinate level, e.g., "kitchen table," instead

of at the basic level, e.g., "table," you don't gain a lot of information about the

object.

What Is It?


Possible Answers

An animalA dog

A bulldog

Superordinate level

Basic level

Subordinate level

Possible Answers

A vehicleA truck

A pickup truck

Superordinate level

Basic level

Subordinate level

Return to Diagram Showing Superordinate, Basic & Subordinate Levels

Information Provided by Categorizations at Different Levels


• If you describe something at the superordinate level, e.g., "furniture," instead

of at the basic level, e.g., "table," you lose a lot of information about the object.

Criteria for Basic Level: Feature Listing

• If you describe something at a subordinate level, e.g., "kitchen table," instead

of at the basic level, e.g., "table," you don't gain a lot of information about the

object.

Behavioral Criteria for Basic Level Categories

Criterion 1 (Feature-Listing): Ask subjects to list features of objects in a category

♦ Category Name = . . . . . . . (fill in the blank, e.g., “furniture” or “chair”)♦ Instruction: “List as many characteristics or attributes that you can think of

which describe the object.”

Examples♦ Category Name: “furniture”

♦ “List as many characteristics or attributes that you can think of which describe furniture.”

♦ Category Name: “chair”

♦ “List as many characteristics or attributes that you can think of which describe chairs.”

♦ Category Name: “armchair”

♦ “List as many characteristics or attributes that you can think of which describe furniture.”


Superordinate Level

Basic Level

Subordinate Level

Behavioral Criteria: Basic Level has Greatest Gain in Features

Behavioral Criteria for Basic Level Categories (cont.)

Criterion 1 (Feature-Listing): Ask subjects to list features of objects in a category

♦ Category Name = . . . . . . . (fill in the blank, e.g., “furniture” or “chair”)♦ Instruction: “List as many characteristics or attributes that you can think of

which describe the object.”

Characteristic of the basic level:♦ Superordinate level – relatively few features are listed

(not many features of “furniture”)

♦ Basic level – many features are listed(Many features associated with “chairs”)

♦ Subordinate level – may have more features than the basic level but the increase is relatively small.(Features listed for “armchair” are not many more than features listed for “chair”)

Psych 355, Miyamoto, Spr '15 12Behavioral Criteria: Free Naming

Behavioral Criteria for Basic Level Categories (cont.)

Criterion 2 (Free Naming): Ask subjects to name a picture of an object

♦ Instruction: “What would you call this?” [show image of an object]

Characteristics of the Basic Level:♦ The basic level is the most commonly used category label.

Example♦ Show subject a picture of an armchair.

♦ The response “chair” is more likely than the response “furniture”.The response “chair” is more likely than the response “armchair”.

Psych 355, Miyamoto, Spr '15 13Behavioral Criteria: Category Verification Time


Criterion 3 (Category Verification): Measure response time for deciding whether an image is an example of a given category

Examples

1st subject hears “FURNITURE”

Next subject sees picture of an armchair.

Correct response = TRUE

1st subject hears “CHAIR”



1st subject hears “ARMCHAIR”




Superordinate Level

Basic Level

Subordinate Level

Behavioral Criteria: Category Verification Time – Basic level Fastest


Criterion 3 (Category Verification): Measure response time for deciding whether an image is an example of a given category

Characteristic of the Basic Level: Categorization decisions are fastest at the basic level.

1st subject hears “FURNITURE”



1st subject hears “CHAIR”



1st subject hears “ARMCHAIR”




Superordinate Level

Basic Level

Subordinate Level

Fastest Categorization Response

Slower Categorization Response

Slower Categorization Response

Fastest Categorization Response

Behavioral Criteria: Summary

Summary: Behavioral Criteria for Basic Level Categories

• Criterion 1 (Feature-Listing)

• Criterion 2 (Free Naming)

• Criterion 3 (Category Verification)

Psych 355, Miyamoto, Spr '15 16Expert Versus Non-Experts

The Basic Level May Not Be the Same for Experts & Non-Experts

• Tanaka and Taylor (1991): Bird experts use specific bird species, e.g., "eagle", "hawk", etc., as if they are the basic level. For the average person, "bird" is basic level, but not for bird experts.

Psych 355, Miyamoto, Spr '15 17Same Slide Without Emphasis Rectangles

basic basic specificspecific

Experts Non-Experts

The Basic Level May Not Be the Same for Experts & Non-Experts

• Tanaka and Taylor (1991): Bird experts use specific bird species, e.g., "eagle", "hawk", etc., as if they are the basic level. For the average person, "bird" is basic level, but not for bird experts.

Psych 355, Miyamoto, Spr '15 18There May Be Cultural Differences in Categorization

basic basic specificspecific

There can be systematic cultural differences in category knowledge

• Medin et al. compared Native American (Menominee Indian) and Euro-American fish experts (fisherman).

♦ Euro-American experts tended to sort fish into goal-related categories, e.g., game fish and non-game fish.

♦ "Native American fish experts ... tended to sort ecologically and were more likely to see positive and reciprocal ecological relations," e.g., fish that live together or live in predator-prey relations.

• Itza Maya in Guatemala categorize birds at a lower level than do typical Americans.

♦ Basic level for Itza Maya is the subordinate level for Americans.

♦ E.g., Itza Maya would say "red hawk" where an American would say "bird."

Psych 355, Miyamoto, Spr '15 19Summary re Category Structure


Summary re Category Structure

• The "basic level" of categorization is the level of category structure

that is usually most useful for members of a given culture.

• The objects that are grouped together in a basic level category ....o share many properties with other objects in the category, i.e., different chairs

share many important properties with each other, and ....o differ in important ways from objects in other categories at the same

level, e.g., chairs differ in important ways from tables, lamps, cars, etc.

• The basic level can differ between experts and non-experts

in a domain, or between members of different cultures.

Brief Mention of Network Models of Concepts

Semantic Networks & Connectionist Models

• Semantic networks & connectionist models – two differentapproaches to modeling concept structure.

♦ Semantic networks & connectionist models use different formalisms.

• Spreading activation – activation of some concepts causes activation in associated concepts.

• Connectionist models focus on learning concept structure.

• Semantic networks focus on modeling human concept structure without modeling how we learn this structure.

[There are different methods for creating models, e.g., some models are based on mathematical or statistical formalisms, other models are based on computer programs.]

Psych 355, Miyamoto, Spr '15 21What Aspects of Network Models Will Be Required on Tests?

Semantic Network Models

• Concepts are arranged in networks that represent the way concepts are organized in the mind.


Example of a Semantic Network

Collins and Quillian (1969)

• Model for how concepts and properties are associated in the mind

• Node = category/concept

• Concepts are linked

• Cognitive economy: shared properties are only stored at higher-level nodes

• Exceptions are stored at lower nodes

• Inheritance♦ Lower-level items share properties of higher-level items


Goldstein Figure 9.12

Using a Semantic Network to Predict Sentence Verification

Collins & Quillian (1969)

• Measure response time to verify whether sentence is TRUE or FALSE("sentence verification" or "semantic memory")

• Theoretical claim of spreading activation theory:

♦ Activation is the arousal level of a node

♦ When a node is activated, activity spreads out along all connected links

♦ Concepts that receive activation are primed and more easily accessed from memory


Goldstein Figure 9.13 (top) & 9.14 (bottom)

Problems with Semantic Networks

• Distance between nodes does not always predict response time patterns.

• Example: A canary is a bird.An ostrich is a bird.

• Example:A pig is a mammal. (RT = 1.476 ms)

A pig is an animal. (RT = 1.268 ms)

• Psychologists are searching for a representation of concepts that predicts behavioral results, but no representation is extremely successful.


Should be equally fast because network distance is the same, but first sentence faster than second.

1st sentence should faster than 2nd sentence because network distance is shorter, but opposite is true.

Summary re Categorization

• Categories are not represented by means of definitions.

• Categories are represented by means of prototypes or exemplars.

• There is a basic level of categorization.

• Cognitive psychologists are searching for a computational model of the representation of category information, and the processing of category information.

Psych 355, Miyamoto, Spr '15 26Question: What Are Neural Representations of Category Knowledge?


Tuesday, May 19, 2015: The Lecture Ended Here

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Category Structure Psychology 355: Cognitive Psychology Instructor: John Miyamoto 05/20 /2015: Lecture 08-2 This Powerpoint presentation may contain macros