Semantic MemorySemantic Memory

Psychology 3717Psychology 3717

IntroductionIntroduction

This is our memory for facts about the worldThis is our memory for facts about the world How do we know that the capital of Viet Nam is How do we know that the capital of Viet Nam is

HanoiHanoi How is this type of information stored?How is this type of information stored? Is there any difference between ‘natural’ and Is there any difference between ‘natural’ and

‘logical’ concepts?‘logical’ concepts? How the heck could we figure this out?How the heck could we figure this out?

TLCTLC

No, not that lame TV channel ful of trading No, not that lame TV channel ful of trading spaces and makeovers….spaces and makeovers….

The Teachable Language ComprehenderThe Teachable Language ComprehenderHierarchical associative network of Hierarchical associative network of

concepts that began as a computer concepts that began as a computer simulationsimulation

bacgroundbacground

Quinlan and his colleagues tried to make a Quinlan and his colleagues tried to make a computer program that would simulate computer program that would simulate how a person learns languagehow a person learns language

Realized that concepts, not words, were Realized that concepts, not words, were the building blocks of knowledgethe building blocks of knowledge

Example ‘the policeman held up his hand Example ‘the policeman held up his hand and the cars stopped (Collins & Quinlan, and the cars stopped (Collins & Quinlan, 1973)1973)

You know exactly what that phrase entailsYou know exactly what that phrase entailsCop is directing trafficCop is directing trafficPeople push pedals etcPeople push pedals etcTacit knowledge if you willTacit knowledge if you willThree types of elements of semantic Three types of elements of semantic

memorymemory

The three elementsThe three elements

Units, properties and pointersUnits, properties and pointersUnit is a thing (the cop, his hand, the car Unit is a thing (the cop, his hand, the car

etc)etc)Properties are conceptual (raising the Properties are conceptual (raising the

hand that sort of thing)hand that sort of thing)Pointers denote specific associationsPointers denote specific associations

So where does this get us?So where does this get us?

Semantic memory then is a HUGE Semantic memory then is a HUGE hierarchical network of relationships hierarchical network of relationships between elementsbetween elements

Is statements then are relationships Is statements then are relationships between a superordinate element and a between a superordinate element and a subordinatesubordinate

A bird is a fish will not produce a yesA bird is a fish will not produce a yesA fish is an animal and a bird is an animal A fish is an animal and a bird is an animal

willwill

Collins and Quinlan (1969)Collins and Quinlan (1969)

A _____ is a ______ statementsA _____ is a ______ statementsSentence verificationSentence verificationRT longer when number of associative RT longer when number of associative

links was greaterlinks was greaterLess relevant property relationships, Less relevant property relationships,

longer RTlonger RT (a canary is yellow is longer than a canary (a canary is yellow is longer than a canary

can breather)can breather)

However…However…

Ok, by this theory, the satement ‘a bear is Ok, by this theory, the satement ‘a bear is a mammal’ should be quicker than ‘a bear a mammal’ should be quicker than ‘a bear is an animal’is an animal’

Ummm, no….Ummm, no….So the ‘semantic distance effect’ does not So the ‘semantic distance effect’ does not

show up hereshow up here

More butsMore buts

Does not deal with the typicality effect at Does not deal with the typicality effect at allall

Does not explain why ‘a robin is a shark’ is Does not explain why ‘a robin is a shark’ is more quickly rejected than ‘a robin is a more quickly rejected than ‘a robin is a salmon’salmon’

Conrad (1972) said that it is the typicality Conrad (1972) said that it is the typicality of the statement itself that is the issueof the statement itself that is the issue

Feature set theoryFeature set theory

Smith, Shoben and Rips (1974)Smith, Shoben and Rips (1974)Concepts stored as sets of attributesConcepts stored as sets of attributesRT then depends on comparing features RT then depends on comparing features

of exemplar with stored conceptof exemplar with stored conceptPredicts the symbolic distance effect (very Predicts the symbolic distance effect (very

similar items take long RTssimilar items take long RTsPredicts the category size effect (concept Predicts the category size effect (concept

to superordinate)to superordinate)

But….But….

You knew there would be a butYou knew there would be a butWhat are the defining features of a What are the defining features of a

conceptconceptWhat is a dog for exampleWhat is a dog for exampleYour idea is different than mineYour idea is different than mineBut we gt the same effects with subjectsBut we gt the same effects with subjects

Spreading activationSpreading activation

Collins and Loftus (1975)Collins and Loftus (1975)Network like TLCNetwork like TLCNOT as rigidly hierarchicalNOT as rigidly hierarchicalStill have units and properties, but not so Still have units and properties, but not so

hierarchicalhierarchicalDistance is importantDistance is important

But..But..

This one sounds better but there is a butThis one sounds better but there is a butDistantly related concepts should give Distantly related concepts should give

longer RTslonger RTsBut ‘a canary is a shark’ takes like no timeBut ‘a canary is a shark’ takes like no time

Propositional network theoryPropositional network theory

Anderson (1983)Anderson (1983)ACT and ACT*ACT and ACT*For example ‘Kurt’s mother sent him a For example ‘Kurt’s mother sent him a

package last week’package last week’Three propositionsThree propositionsMore propositions, sentences take longer, More propositions, sentences take longer,

even with fewer wordseven with fewer words

Neural network modelsNeural network models

Units or nodes that are like neurons, on and offUnits or nodes that are like neurons, on and off But, units have a threshold and once acticavted But, units have a threshold and once acticavted

past this threshold you get ‘firing’past this threshold you get ‘firing’ Units are connected either excitatorily or Units are connected either excitatorily or

inhibtorilyinhibtorily There are activation rulesThere are activation rules Output rules, how a unit sends info to next unitOutput rules, how a unit sends info to next unit Learning rulesLearning rules Groups of units or modules, are devoted to Groups of units or modules, are devoted to

specific cognitive functionsspecific cognitive functions

propertiesproperties

Content addressable memoryContent addressable memoryNetwork makes guessesNetwork makes guessesNetwork makes spontaneous Network makes spontaneous

generalizationsgeneralizations

conclusionsconclusions

I don’t want to get too bogged down in this I don’t want to get too bogged down in this but, I think that we can make a few but, I think that we can make a few statementsstatements

All the theories are about connectionsAll the theories are about connectionsProbably NOT hierarchical, completelyProbably NOT hierarchical, completelyActivation probably spreadsActivation probably spreadsThis stuff can get way hard….This stuff can get way hard….