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Representational Hypotheses in Cognitive Psychology Psychology 355: Cognitive Psychology Instructor: John Miyamoto 05/18/2016: Lecture 08-3 Note: This Powerpoint presentation may contain macros that I wrote to help me create the slides. The macros aren’t needed to view the slides. You can disable or delete the macros without any change to the presentation. 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 22 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