1. Categorization

2. Concepts and Categorization  Concepts allow for efficient categorization  But, how are concepts represented?  What “defines” an object?  Primary qualities  Secondary qualities  How do we decide ‘object X’ belongs with ‘category Y’?

3. Natural Levels of Categorization  Rosh et al.’s (1976) three “levels” of categorization  Superordinate level  Basic level  Subordinate level Superordinate Level Basic Level Subordinate Example 1 Subordinate Example 2 Music InstrumentsGuitarFolk GuitarClassical Guitar PianoGrand PianoUpright Piano DrumKettle DrumBass Drum FruitAppleDelicious AppleMackintosh Apple PeachFreestone PeachCling Peach GrapesConcord GrapesGreen Seedless Grapes ToolsHammerBall-peen HammerClaw Hammer SawHack HandsawCross-cutting Handsaw ScrewdriverPhillips ScrewdriverRegular Screwdriver ClothingPantsLevi’sDouble-knit Pants SocksKnee SocksAnkle Socks ShirtDress ShirtKnit Shirt FurnitureTableKitchen TableDining Room Table LampFloor LampDesk Lamp ChairKitchen ChairLiving-room Chair VehiclesCarSports CarFour-door Sedan BusCity BusCross-country Bus TruckPickup TruckTractor-trailer Truck

4. Natural Levels of Classification  Rosh et al. (1976)  Presented subjects with category labels  Subjects named as many features in common to all members of the given category label Level:SuperordinateBasic LevelSubordinateSuperordinate Label:(Clothing)(Pants)(Levi’s)(Knit Pants) You wear it Keeps you warm Legs Buttons Belt Loops Pockets Cloth Two Legs Blue Comfortable Stretchy

5. Natural Levels of Classification  Rosh et al. (1976)  Examined number of attributes at each category level  “Best” level of categorization is basic level  Why not superordinate level?  Why not subordinate level? Raw Tallies CategorySuperordinateBasic LevelSubordinate Musical Instruments16.08.5 Fruit712.314.7 Tools38.39.7 Clothing310.012.0 Furniture39.010.3 Vehicles48.711.2 Mean3.509.0511.07

6. Natural Levels of Classification  Rosh et al. (1976) basic level category “models”

7. Tanaka and Taylor (1991)  Expertise guides classification  What is this?  And this? Vehicle (or Ship) v Starship v Ambassador Class Vehicle (or Ship) v Romulan Warbird v D’deridex Class

8. Tanaka and Taylor (1991)  Bird experts vs. dog experts  Subjects identified pictures of specific birds and dogs (subordinate-level) or common birds and dogs (basic-level)

9. Tanaka and Taylor (1991)  Expertise sped responses subordinate exemplars, and non-experts faster at basic level exemplars

10. Categorization  OK, so how do we actually categorize?  Definitional approach  Compare features of item defining characteristics for categories  Problem is what defines a defining characteristic?  Nearest-neighbor rule  Select the category containing an item that is most similar to the item to be classified  Average distance rule  Select the category containing items that have the greatest average similarity to the item to be classified  Prototype rule…

11. Typicality  Objects may be classified by comparison to prototypes  Rosch (1976) found objects differ in typicality  High prototypicality  Low prototypicality 7654321 Category: Birds (Proto)TypicalityLowHigh Sparrow (1.18) Owl (2.96) Penguin (4.53) Bat (6.15)

12. Typicality  Items are listed in order of typicality under each superodrinate category Superordinate Category Rank in TypicalityFurnitureVehiclesFruitWeaponsVegetablesClothing 1ChairCarOrangeGunPeasPants 2SofaTruckAppleKnifeCarrotsShirt 3TableBusBananaSwordString BeansDress 4DresserMotorcyclePeachBombSpinachSkirt 5DeskTrainPearHand GrenadeBroccoliJacket 6BedTrolley CarApricotSpearAsparagusCoat 7BookcaseBicyclePlumCanonCornSweater 8FootstoolAirplaneGrapeBow & ArrowCauliflowerUnderpants 9LampBoatStrawberryClubBrussels SproutsSocks 10PianoTractorGrapefruitTankLettucePajamas 11CushionCartPineappleTear GasBeetsBathing Suit 12MirrorWheelchairBlueberryWhipTomatoShoes 13RugTankLemonIce PickLima BeansVest 14RadioRaftWatermelonFistsEggplantTie 15StoveSledHoneydewRocketOnionMittens 16ClockHorsePomegranatePoisonPotatoHat 17PictureBlimpDateScissorsYamApron 18ClosetSkatesCoconutWordsMushroomPurse 19VaseWheelbarrowTomatoFootPumpkinWristwatch 20TelephoneElevatorOliveScrewdriverRiceNecklace

13. Typicality  Basic level category “models” may be prototypes

14. Typicality  Smith, Shoben and Rips (1974)  Sentence verification task  Typicality effect