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Cognitive Psychology Nov 7th.docx

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University of Guelph
PSYC 1000
Linda Hunter

Spreading Activation in a Hierarchical Model of Semantic Memory (Collins and Quillian) Also a ZAPS experiment Sentence verification time increases with number of nodes through which activation must spread A Canary is a Canary: Base line- activation does not spread to another node in the hierarchy to the question A Canary is a Bird: Activation spreads one node higher in the hierarchy to answer the question A Canary is an Animal: Activation spreads two nodes higher in the hierarchy to answer the questions Typicality Effects in Semantic Memory: -A pig is a mammal= 1680 milliseconds -A pig is an animal = 1476 milliseconds -But mammal should be faster because it is lower in the hierarchy than animal -Animal is more strongly associated with pig than mammal is associated with pig so “pig is an animal” is verified faster. A canary or a robin is more typical of a birds than an ostrich or a peacock soo.. -“A canary is a bird” is verified fasted than “ostrich is a bird” even though they are all at the same level in the hierarchy. Collins and Loftus (1975) Associative Model of Semantic Memory Collins and Loftus (1975) abandoned a sematic hierarchy and replaced it with an associative network that considers the strength of association between nodes -More typical and or more strongly associated items have shorter links Associative models tend to be very general but are also powerful and account for more of the data than hierarchical models Feature List Models of Semantic Memory (Smith, Shoben, Rips, 1974) Concepts in semantic memory are represented by feature lists of two kinds: -Defining Features: Essential for the definition of the concept -BIRD: Physical object, living, animate, feathered -Characteristic Features: Common features but NOT essential for defining concept -BIRD: Fly’s, red-breasted, perches in trees, eats worms, shows up in the spring Comparison Processes in Semantic Memory (Smith, Shoben, Rips, 1974) A Robin is Bird vs A Robin is Bulldozer Stage 1: Rapid, global feature comparison -Fast NO to “A robin is a bulldozer” is due to very low feature overlap between robins and bulldozers -Fast YES to “A Robin is a bird” is due to very high overlap between robins and birds A Bat is a Bird vs A Chicken is a Bird Stage 2= Slower, deliberate comparison of defining features if stage 1 does not produce a match -Slow NO to “bat is a bird” is due to incomplete overlap with defining features (feathers) -Slow YES to “Chicken is a bird” is due to a match on defining features even though there is a mismatch on the characteristic feature of flying Comments the Feature List Model -Feature Overlap: ROBIN is a BIRD is faster than BIRD is an ANIMAL because ROBIN is a BIRD has higher feature overlap and not because they are in different position in a semantic hierarchy. -Typicality Effects: Robins tend to be faster than chickens because robins have higher feature overlap with the bird category than chickens have. -Hierarchical models cannot account for typicality Issues in Categorization: Many categories do not have an explicit definition specifying what or who is in or out of the category Category members tend to be graded -A robin is an excellent example of the category bird whereas chicken and ostrich are not -Chicken and ostrich are near the fuzzy boundary of the bird category whereas bat is outside the category People can rate the typicality of examples of a category -Degree of typicality yields strong effects in sentence verification tasks, memory production tasks, category judgement tasks, etc. Family Resemblance Among Members of a Category -Extent to which a member of a category has features in common with all of the features of a category -Family resemblance is a matter of degree rather all or none and tend to defy definition Typical Family Baron-Cohen “Family” Cub Category: Examples vary considerably in size and shape Grandfather Category: Definition of grandfather results in both typical and atypical members being included in the category Basic Level Categories (Rosch, 1975) Natural level of categorization that is not too general and not too specific - Guitar is a basic level category - Musical instrument is a superordinate category -Electric guitar and acoustic guitar are subordinate categories Basic level categories are - Easier to access and use -Learned earlier and more easily -Often regarded as typical Prototypes and Categorization Prototypes correspond to the average of all the instances of a category or the “center” of a category -A prototype defines the category but may be abstract or ideal and not correspond to an example that was actually experienced Degree of category membership of examples is determined by their “distance” or similarity to the prototype -Prototypes can vary across individuals How are Category Examples Recognized in a Prototype Model? The prototype is retrieved and the example is compared to it -Responses are faster and more accurate for examples that are close or similar to the prototype -Typical items (ROBIN) tend to match the prototype (BIRD) very closely whereas atypical items (OSTRICH) do not Problems with Prototype Models of Categorization Similar to a feature theory because a prototype can be defined as a bundle of defining and characteristic features. -Goal-Derived Categories: Things to take to a drivers test -Ad-hoc Categories: Things to remember about your Aunt Grace on her birthday -These categories functions like normal categories because -They exhibit typicality effects and graded membership but…it is more difficult to identify the prototypes for these categories Example Models of Categorization Compare example with first example that you retrieve from memory -Typical items tend to be retrieved and matched more easily than less typical items Tendency to rely on examples when one is a novice and just learning about a category -Prototypes may be used later in learning when expertise is acquired We probably use both prototypes and examples in everyday categorization Rules and/or Prototypes and Specific Examples are used in Classification Real world medical diagnosis: Skin Disorders -Residents and general practitioners were better at diagnosing cases that were similar to previously seen cases Examples similar ot the current case may be activated along with the general diagnostic category during t
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