1. Category Structure Psychology 355: Cognitive Psychology Instructor: John Miyamoto 05/20 /2015: Lecture 08-2 This Powerpoint presentation may contain macros that were used to create the slides. The macros aren’t needed to view the slides. If necessary, you can disable the macros without any change to the presentation.

2. Outline Basic level of categorization. Network models of category structure. Connectionist models. The neural representation of category information. Psych 355, Miyamoto, Spr '15 2 Why Category Structure Is Important for Cog Psych Theory? very brief

3. 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. ♦ E.g., What is the “semantic code” in which LTM’s are stored? ♦ 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

4. 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 4 Cat Image with Associated Properties - Reminder that We Are Discussing a Category Representation.

5. Psych 355, Miyamoto, Spr '15 5 Knowing the Category Provides a Lot of Information Is There a Basic Level of Categorization?

6. Psych 355, Miyamoto, Spr '15 6 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

7. Psych 355, Miyamoto, Spr '15 7 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. Information Gain at Different Levels of Categorization

8. Information Provided by Categorizations at Different Levels Psych 355, Miyamoto, Spr '15 8 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.

9. What Is It? Psych 355, Miyamoto, Spr '15 9 Possible Answers An animal A dog A bulldog Superordinate level Basic level Subordinate level Possible Answers A vehicle A truck A pickup truck Superordinate level Basic level Subordinate level Return to Diagram Showing Superordinate, Basic & Subordinate Levels

10. Information Provided by Categorizations at Different Levels Psych 355, Miyamoto, Spr '15 10 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.

11. 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.” Psych 355, Miyamoto, Spr '15 11 Superordinate Level Basic Level Subordinate Level Behavioral Criteria: Basic Level has Greatest Gain in Features

12. 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 12 Behavioral Criteria: Free Naming

13. 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 13 Behavioral Criteria: Category Verification Time

14. Behavioral Criteria for Basic Level Categories Criterion 3 (Category Verification): Measure response time for deciding whether an image is an example of a given category Examples 1 st subject hears “FURNITURE” Next subject sees picture of an armchair. Correct response = TRUE 1 st subject hears “CHAIR” Next subject sees picture of an armchair. Correct response = TRUE 1 st subject hears “ARMCHAIR” Next subject sees picture of an armchair. Correct response = TRUE Psych 355, Miyamoto, Spr '15 14 Superordinate Level Basic Level Subordinate Level Behavioral Criteria: Category Verification Time – Basic level Fastest

15. Behavioral Criteria for Basic Level Categories 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. 1 st subject hears “FURNITURE” Next subject sees picture of an armchair. Correct response = TRUE 1 st subject hears “CHAIR” Next subject sees picture of an armchair. Correct response = TRUE 1 st subject hears “ARMCHAIR” Next subject sees picture of an armchair. Correct response = TRUE Psych 355, Miyamoto, Spr '15 15 Superordinate Level Basic Level Subordinate Level Fastest Categorization Response Slower Categorization Response Fastest Categorization Response Behavioral Criteria: Summary

16. Summary: Behavioral Criteria for Basic Level Categories Criterion 1 (Feature-Listing) Criterion 2 (Free Naming) Criterion 3 (Category Verification) Psych 355, Miyamoto, Spr '15 16 Expert Versus Non-Experts

17. 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 17 Same Slide Without Emphasis Rectangles basic specific Experts Non-Experts

18. 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 18 There May Be Cultural Differences in Categorization basic specific

19. 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 19 Summary re Category Structure

20. Psych 355, Miyamoto, Spr '15 20 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. Brief Mention of Network Models of Concepts

21. Semantic Networks & Connectionist Models 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. 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 21 What Aspects of Network Models Will Be Required on Tests?

22. Semantic Network Models Concepts are arranged in networks that represent the way concepts are organized in the mind. Psych 355, Miyamoto, Spr '15 22

23. 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 Psych 355, Miyamoto, Spr '15 23 Goldstein Figure 9.12

24. 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 Psych 355, Miyamoto, Spr '15 24 Goldstein Figure 9.13 (top) & 9.14 (bottom)

25. 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. Psych 355, Miyamoto, Spr '15 25 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.

26. 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 26 Question: What Are Neural Representations of Category Knowledge?

27. Psych 355, Miyamoto, Spr '15 27 Tuesday, May 19, 2015 : The Lecture Ended Here