psy 323 – cognition chapter 9: knowledge. categorization ◦ process by which things are placed...
TRANSCRIPT
Categorization◦Process by which things are placed into groups
Concept◦Mental groupings of similar objects, events, ideas, and
people
Knowing about something is in a category gives us a great deal of information about it.
How Are Objects Placed Into Categories?
Classic ViewDefinitional approach to categorization Probabilistic TheoriesThe Prototype ApproachThe Exemplar Approach
Classic View
Definitional approach to categorization We create categories based on a system of rules or definitionsRules must identify necessary and sufficient features (often referred to as concepts)
Limitations to Classic View
Do we really use rules to create categories? Our semantic memory probably doesn’t rely on such thingsMany everyday categories are rule-breakers
Limitations to Classic ViewGraded Membership•Members of a category vary in how truly they fit the category
Classic View
Wittgenstein (1953)Family resemblance refers to the idea that things in a particular category resemble one another in a number of waysThus, instead of setting definite criteria that every member of a category must meet, the family resemblance approach allows for some variation within a category
Probabilistic Theories
The Prototype ApproachThe central core instance of a categoryThe average of all your experiencesIdealized representation (doesn’t correspond exactly to any member)
The Prototype Approach
Lee, Byatt, & Rhodes (2000)Participants more accurately recognized a caricature of Arnold Schwarzenegger than a real picture of Arnold
Testing the Prototype Notion
Malt & Smith (1984)
TR = Typicality Rating (based on 0-7 scale)
.FRUIT BIRD
STIMULUS TR STIMULUS TR
Apple 6.2 Robin 6.9
Peach 5.8 Seagull 6.3
Pear 5.2 Owl 5.0
Watermelon 4.1 Chicken 3.9
Coconut 3.1 Penguin 2.6
Olive 2.2 Bat 1.5
Evidence Supporting Prototype Approach
Family ResemblanceDistribution of attributesRatings task TypicalitySentence Verification Task: Yes/No questions Picture Identification Task: Yes/No questions NamingProduction tasks
Family Resemblance Test
Rosch & Mervis (1975)Distribution of attributes (features)The most typical item in a category has the most features in common with other members of the category will be given highest ratingThese items are ideal examples and may be referred to as “prototype”
See next slide
Demo: Family Resemblance Test
ChairSofaBedMirrorTelephoneTV
Take 30s to write down the characteristics for each of the items
Rosch & Mervis (1975)
Rosch (1975)
Family Resemblance Test
Results
Procedure•Ratings task•Participants judged objects on a scale of 1 (good example of a category) to 7 (poor example)
Sentence Verification TaskTypicality EffectStatements about prototypical objects are verified quickly.
– Is an apple a fruit? Yes / No– Is pomegranate a fruit? Yes / No
Smith et al. (1974)
Naming: Production Tasks
Prototypical Objects Are Named First When participants are asked to list as many objects in a category as possible, they tend to list the most prototypical members of the category first
Mervis et al. (1976)
Limitations to Prototype Theory
Circularity ProblemHow do we know what experiences should be averaged to form a category without knowing what the category is ahead of time?Early studies used the same data to explain why something was a prototype and why something was not a prototype
Probabilistic Theories
Exemplar TheoryMentally taking in each experience or encounter one has had with members of that category; thinking about examplesExemplars are actual members of a category that someone has encountered in the past
WHICH APPROACH WORKS BETTER:PROTOTYPES OR EXEMPLARS?
Based on the results of a number of research studies, some researchers have concluded that people may use both approachesIt has been proposed that as we initially learn about a category, we may average exemplars into a prototype; then, later in learning, some of the exemplar information becomes stronger Other research indicates that the exemplar approach may work best for small categories, such as “U.S. presidents” or “Mountains taller than 15,000 feet,” and the prototype approach may work best for larger categories, such as “birds” or “automobiles”
Hierarchical Organization of Categories
Largest number of features Used most often
Basic Level
Bean Bag, Robin
Chair, Bird
Furniture, Animal
Subordinate
Superordinate
Rosch & Mervis (1975)
Basic-Level is Special
People almost exclusively use basic-level names in free-naming tasks
Children learn basic-level concepts sooner than other levels
Basic-level is much more common in adult discourse than names for superordinate categories
Different cultures tend to use the same basic-level categories, at least for living things
Semantic Network Model
Nodes represent concepts in memoryRelations represented links among sets
of nodesSpreading activation
Robin WingsProperty
Collins & Quillian’s Model (1969)
Spreading activationActivation is the arousal level of a nodeSpreads down linksUsed to extract information from network
Structure is hierarchicalTime to retrieve information based on number of links
See next slide
Collins & Quillian’s Model (1969)
Has skin
Breathes
Eats
Animal
Salmon
Has fins
Has gills
swim
Is pink
Lays eggs upstream
Is edible
Has spots
4 legs
barks
Has fur
Fish
Black & white
Dalmatian
Dog
Skinny tail
Credits
Some of the slides in this presentation prepared with the assistance of the following web sites: http://erasmus-mundus.univ-paris1.fr/fichiers_etudiants/2488_dissertation.pdf
http://www.academia.edu/6690750/Perceptual_interpretation
www.itu.dk/.../2011-Spring-HIP-Lecture09-... www.tamu.edu/faculty/takashi/.../Ch%209%20Knowledge.ppt