09 - Semantic memory

09 - Semantic memory - Long Term Memory Structure Semantic...

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1 Semantic Memory 1 Long Term Memory Structure Declarative (Explicit) Non-declarative (Implicit) 2 Semantic Episodic Perceptual Procedural STM Stores general world knowledge (e.g., concepts and categories). Two early models of semantic memory • The hierarchical model (Collins & Quillian, 1969) 3 • The spreading activation model (Collins & Loftus, 1975) Animal Collins and Quillian's (1969) Hierarchical model of semantic memory 4 Bird Canary 1. Concept are organized in a hierarchy. Animal Breathes Has skin Eats Collins and Quillian's (1969) Hierarchical model of semantic memory 5 Bird Canary Is yellow Can sing Can Fly Has wings 2. Cognitive economy: Properties are associated with the most general concepts for which they are true. Animal Breathes Has skin Eats Collins and Quillian's (1969) Hierarchical model of semantic memory 6 Bird Canary Is yellow Can sing Can Fly Has wings 3. Retrieving information from the network takes time.
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2 Animal Breathes Has skin Eats Do canaries have skin? Yes. (1433 ms) 7 Bird Canary Is yellow Can sing Can Fly Has wings 3. Retrieving information from the network takes time. Animal Breathes Has skin Eats Two computational predictions t up t 8 Bird Canary Is yellow Can sing Can Fly Has wings 1. Time to move up in the hierarchy and time to retrieve property information are additive . t up t property property t property Animal Breathes Has skin Eats Two computational predictions t up 9 Bird Canary Is yellow Can sing Can Fly Has wings 2. Time to retrieve a property from a node is independent of the level of the node. t up t property t property t property Collins and Quillian's (1969) Experiment ± The participants were asked to evaluate the truth value of sentences thought to 10 reflect the organization of semantic memory. - Is a canary a bird? Yes (+ RT) - Do canaries swim? No (+ RT) Collins and Quillian's (1969) Experiment Sentence type Superset relations Property relations 11 Level (S) (P) 0 A canary is a canary (S0). A canary is yellow (P0). 1 A canary is a bird (S1). A canary can fly (P1). 2 A canary is an animal (S2). A canary breathes (P2). Results 900 1000 1100 1200 012 Superset relations Property verification S0 S1 ? ? t up t property
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3 Collins and Quillian (1969) ± Conclusions: 1. The assumptions of the hierarchical model 13 are supported . 2. Moving up one level in the hierarchy takes 75 ms and retrieving a property takes 225 ms . A Problem with the Hierarchical Model 1. Response times obtained in semantic categorization tasks do not all support the hierarchical model: 14 Sentences Response times Canaries (S0) are birds (S1). 1279 ms Penguins (S0) are birds (S1). 1466 ms Animal Wings Breath Skin Eat Quillian and Loftus' (1975) Spreading activation model 15 Bird Canary Yellow Sing Fly 1. Both concepts and properties are represented by nodes. Animal Wings Breath Skin Eat Quillian and Loftus' (1975) Spreading activation model 16 Bird Canary Yellow Sing Fly 2. The organization is non-hierarchical. Every node is connected to every node.
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This note was uploaded on 02/21/2012 for the course PYSC 405 taught by Professor Ferreira during the Fall '11 term at South Carolina.

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09 - Semantic memory - Long Term Memory Structure Semantic...

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