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Representational Hypotheses
in Cognitive Psychology
Psychology 355: Cognitive Psychology
Instructor: John Miyamoto
05/18/2016: Lecture 08-3
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Outline
• Representational hypotheses - what are they?
• The centrality of human language capacity in the theory of cognition
• Semantic network models - a very brief discussion
• Is there a basic level in human conceptual representations?
Lecture probably
ends here
• Neuropsychological representations of categories and concepts
Psych 355, Miyamoto, Spr ‘16
Cognitive Theory = { Representational Hypotheses + Processing Hypotheses }
2
Representational Hypotheses in Cog Psych
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
Psych 355, Miyamoto, Spr '15
Mental Representations & Their Uses
3
Levels of Representation in Language
Theories of human language capacity propose representational
hypotheses at many levels.
• Articulatory and acoustical phonetics - the study of the muscular
coordination in speech and acoustical patterns in the speech signal.
• Phonology - the study of the sound structures of languages.
• Syntax - theories of sentence structure and its relation
to speech context and meaning.
• Semantics - theories of the relation between language structure
and meaning.
Psych 355,, Miyamoto, Spr '16
Language-Like Representations in Cognition
4
Symbolic Representations in Cognition
• The motor theory of speech comprehension:
A link between speech production and speech comprehension.
• Models of language syntax
♦
Cognitive, computational and/or neuropsych models of language processing
with emphasis on sentence structure.
• Inference in language use - is it a logic? is it a computer program?
The modeling of human language capacity
is a major concern of cognitive science.
cog psych is part of cognitive science;
other parts include philosophy, linguistics,
computer science, neuroscience, anthropology
Psych 355,, Miyamoto, Spr '16
Semantic Networks & Connectionist Models
5
Semantic Networks & Connectionist Models
SKIM
• Semantic networks & connectionist models – two different
approaches 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.
[This topic will be omitted from Psych 355 this quarter.]
• Semantic networks focus on modeling human concept
structure without modeling how we learn this structure.
• Psych 355 will briefly discuss semantic network models and
ignore connectionist models.
Psych 355, Miyamoto, Spr '16
Semantic Network Models
6
Semantic Network Models
• Concepts are arranged in networks that represent the way concepts
are organized in the mind.
• Any specific network model must explain:
♦
what is the relationship between the structure of the network and human
thinking or behavior;
♦
what are the rules by which representations are constructed within the
model;
♦
how to derive predictions from the model to different aspects of human
behavior.
Psych 355, Miyamoto, Spr '16
Example of a Semantic Network
7
Example of a Semantic Network
Collins and Quillian (1969)
SKIM
Goldstein Figure 9.12
• 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
Psych 355, Miyamoto, Spr '16
8
Using a Semantic Network to Predict Sentence Verification
Goldstein Figure 9.13 (top) & 9.14 (bottom)
Collins & Quillian (1969)
• Measure response time to
verify whether sentence is
TRUE or FALSE
("sentence verification" or "semantic memory")
• 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
SKIM
Psych 355, Miyamoto, Spr '16
Summary re Semantic Networks
9
Summary re Semantic Network Models
• Concepts are represented as nodes in a semantic network.
• What do semantic network models (SNM's) do?
♦
SNM's explain the relationship between the network structure and human
reasoning and behavior.
♦
SNM's yield predictions for cognitive experiments like semantic memory
experiments, categorization judgments and causal inferences.
♦
SNM's can be part of a learning model that predict how a learner learns new
concepts and conceptual relationships.
• There are many different SNM's that are devised for different research
problems. They tend to be complicated.
Psych 355,, Miyamoto, Spr '16
Reminder: Cat Picture - Transition to Basic Levels in Categorization
10
Knowing the Category Provides a Lot of Information
Psych 355, Miyamoto, Spr '16
Is There a Basic Level of Categorization?
11
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?
Psych 355, Miyamoto, Spr '16
Basic Level Versus Superordinate Level: Amount of Feature Sharing
12
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:
♦
Within a basic level category,
objects share many features with each other.
♦
Between different categories at the basic level,
objects are very different from each other.
Psych 355, Miyamoto, Spr '16
Basic Level Versus Subordinate Level: Amount of Feature Sharing
13
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:
♦
Within a basic level category,
objects share many features with each other.
♦
Between different categories at the basic level,
objects are very different from each other.
Psych 355, Miyamoto, Spr '16
Same Slide Without Emphasis Rectangles
14
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:
♦
Within a basic level category,
objects share many features with each other.
♦
Between different categories at the basic level,
objects are very different from each other.
Psych 355, Miyamoto, Spr '16
Information Gain at Different Levels of Categorization
15
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.
• 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.
Psych 355, Miyamoto, Spr '16
Concrete Example with Images of a Bull Do and a Pickup Truck
16
What Is It?
Possible Answers
Superordinate level
An animal
A dog
Basic level
A bulldog
Subordinate level
Psych 355, Miyamoto, Spr '16
Possible Answers
Superordinate level
A vehicle
A truck
Basic level
A pickup truck Subordinate level
Return to Diagram Showing Superordinate, Basic & Subordinate Levels
17
Information Provided by Categorizations at Different Levels
• The basic level is the level at which we typically categorize everyday
objects.
• We are capable of categorizing objects at superordinate or subordinate
levels, if required to do so by a situation or task.
Psych 355, Miyamoto, Spr '16
Criteria for Basic Level: Feature Listing
18
Behavioral Criteria for Basic Level Categories
Skim
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
Categorization: FURNITURE
♦
“List as many characteristics or attributes
that you can think of which describe furniture.”
Superordinate Level
Categorization: CHAIR
♦
“List as many characteristics or attributes
that you can think of which describe chairs.”
Basic Level
Categorization: ARMCHAIR
♦
“List as many characteristics or attributes
that you can think of which describe furniture.”
Psych 355, Miyamoto, Spr '16
Subordinate Level
Behavioral Criteria: Basic Level has Greatest Gain in Features
19
Behavioral Criteria for Basic Level Categories (cont.)
Skim
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 '16
Behavioral Criteria: Free Naming
20
Behavioral Criteria for Basic Level Categories (cont.)
Skim
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 '16
Behavioral Criteria: Category Verification Time
21
Behavioral Criteria for Basic Level Categories
Skim
Criterion 3 (Category Verification):
Measure response time for deciding whether an image
is an example of a given category
Examples
1st subject hears “FURNITURE”
Superordinate Level
Next subject sees picture of an armchair.
Correct response = TRUE
1st subject hears “CHAIR”
Basic Level
Next subject sees picture of an armchair.
Correct response = TRUE
1st subject hears “ARMCHAIR”
Subordinate Level
Next subject sees picture of an armchair.
Correct response = TRUE
Psych 355, Miyamoto, Spr '16
Behavioral Criteria: Category Verification Time – Basic level Fastest
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Behavioral Criteria for Basic Level Categories
Skim
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”
Next subject sees picture of an armchair.
Correct response = TRUE
1st subject hears “CHAIR”
Next subject sees picture of an armchair.
Correct response = TRUE
1st subject hears “ARMCHAIR”
Next subject sees picture of an armchair.
Superordinate Level
Slower Categorization Response
Basic Level
Fastest Categorization Response
Subordinate Level
Slower Categorization Response
Correct response = TRUE
Psych 355, Miyamoto, Spr '16
Behavioral Criteria: Summary
23
Summary: Behavioral Criteria for Basic Level Categories
Skim
.
• Criterion 1 (Feature-Listing)
• Criterion 2 (Free Naming)
• Criterion 3 (Category Verification)
Psych 355, Miyamoto, Spr '16
Expert Versus Non-Experts
24
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.
Experts
basic
Psych 355, Miyamoto, Spr '16
specific
Non-Experts
basic
specific
Same Slide Without Emphasis Rectangles
25
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.
basic
Psych 355, Miyamoto, Spr '16
specific
basic
specific
There May Be Cultural Differences in Categorization
26
There can be systematic cultural differences
in category knowledge
• Medin et al. compared Native American (Menominee Indian) and EuroAmerican 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 '16
Summary re Category Structure
27
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 ....
♦
share many properties with other objects in the category, i.e., different
chairs share many important properties with each other, and ....
♦
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.
Psych 355, Miyamoto, Spr '16
What Is the Neural Representation of Category Knowledge?
28
Wednesday, May 18, 2016: The Lecture Ended Here
Psych 355,, Miyamoto, Spr '16
29