7-Models of Word Naming

8/12/2019 7-Models of Word Naming

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Kana

Syllabic script

Sublexical processing

Left hemisphere

Deep dyslexia

Kanji

logographic and

ideographic script

Lexical processing

Right hemisphere

Surface dyslexia


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Ideographic language

2 routes:

1.

Route that associates the symbolwith correct pronunciation

2. One that uses part of the symbol


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1. There are lexical effects for

nonwords and regularity effects for

words.

2. Any model must also be able to

account for the pattern of

dissociations found in acquired

dyslexia.


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1. THREE-ROUTE MODEL (Morton

and Patterson)


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Non-lexical route for assembling

pronunciations from sublexical grapheme-to-

phoneme conversion

The direct route is split into a semantic andnon-semantic direct route.

Surface dyslexia- loss of the direct route

Phonological dyslexia- loss of the indirect

routeDeep dyslexia- remains mysterious

-can only read through the

lexical-semantic route


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Different levels of spelling-

to-sound information

combine in an interactiveactivation network to

determine the final

pronunciation of a word.


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Maintains the

basic

architecture of

the dual routemodel but

makes use of

the cascadingprocess.


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The only direct route is readingthrough the semantics.

How does this model account fornon-semantic reading?

-activation from the sublexicalroute combines (or is summated) with

the activation trickling down from thedamaged direct route to ensure thecorrect pronunciation.


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It is a form of single-route

model that provides an explicit

mechanism for how wepronounce nonwords.

Proposes that we pronouncenonwords and new words by

analogy with other words.


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Example 1.:

gang

activates

hang, rang, sang and bang


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Example 2.:

mave

activatesgave, rave and save

also, it activates its conflicting enemy

haveWhich slows down the pronunciation of mave


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In order to name by analogy, you have to findcandidate words containing appropriateorthographic segments.

Example: mave (-ave)

gave, rave and save

Then, obtain the phonological representationof the segments and assemble the complete

phonology. Example:

gave, rave and save

mave


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First, the models did not make clear how the

input is segmented in an appropriate way.

Second, the models make incorrect

predictions about how nonwords should bepronounced.

Third, it appears to make incorrect

predictions about how long it takes us to

make regularization errors. Finally, it is not clear how analogy models

account for the dissociations found in

acquired dyslexia.


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1. SM MODEL or TRIANGLE MODEL(Seidenberg and McClelland)

Semantic

Orthographic Phonological


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It provides an account of how readers

recognize letter strings as words and

pronounce them.

reading and speech involve three types of

code: orthographic, semantic and

phonological

-connected with feedback connections

There is only one route from orthography to

phonology.


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Semantic

Orthographic Phonological


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3 levels: input, hidden and output


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Weights of connections are learned.This network learns to associate aphonological input with an

orthographic input by being givenrepeated exposure to word-pronunciation pairs.

It learns using an algorithm called

back-propagation.-involves slowly reducing the discrepancy

between the desired and actual outputs of thenetwork by changing the weights ofconnections


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The training corpus comprised all 2987

uninflected monosyllabic words of at least 3

or more letters in English language present in

the Kucera and Francis word corpus.

Each trial consisted of the presentation of a

letter string that was converted into the

appropriate pattern of activation over theorthographic units. This in turn fed forward

to the phonological units by the way of the

hidden units.


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The ease with which a word is learned by the

network, and the effect it has on similar

words, depends to some extent on its

frequency

After training, the network was tested by

presenting letter strings and computing the

orthographic and phonological error scores.

Error score is a measure of the averagedifference between the actual and desired

output of each of the output units across all

pattern.


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Phonological error scores were generated by

applying input to the orthographic units and

measured by the output of the phonological

units. It is interpreted as reflecting

performance on naming task.

Orthographic error scores were generated by

comparing the pattern of activation input to

the orthographic units with the patternproduced through feedback from the hidden

units. It is interpreted as a measure of

reflecting the performance of the model in a

lexical decision task.


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Showed that the model fitted human

data on a wide range of inputs. For

example: regular words such as

gave were pronounced fasterthan exception words like have.


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There is only one set of hidden

units and only one process is used

to name regular, exception and

novel items.

There is no one-to-one

correspondence between hidden

units and lexical items; each wordis represented by a pattern of

activation over the hidden units.


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Lexical memory does not consist ofentries for individual words.Orthographic neighbors do notinfluence the pronunciation of a word

directly at the time of processing;instead regularity effects inpronunciation derive from statisticalregularities in the words of the

training corpus.Lexical processing therefore involves

the activation of information and isnot an all-in-one event.


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Coltheart et al: only showed how skilledreaders read exemption words aloud.

Brener et al: the models performance on

nonwords is impaired from the beginning,its account of surface dyslexia wasproblematic and of phonological dyslexiawas non-existent

Norris: it could not account for the abilityof readers to shift strategically betweenreliance on lexical and sublexicalinformation


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Better information in reading

nonwords and explain the

interaction we observe betweenword consistency and frequency.

This, also provides better

account for dyslexia.


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Patterson, Seidenberg, and McClelland

artificially changed or lesioned the SM

network after the learning phase by

destroying hidden units or connection

weights and then observing the behavior of

the model. Its performance resembled the

reading of a surface dyslexic.


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Patterson et al.: 3 types of lesion

1. Early weights (damage to the connection

between the orthographic input and hidden

units)2. Late weights (damage to the connection

between the hidden units and phonological

input)

3. Damage to the hidden units themselves


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Two consequences:

1. Damage was measured by the

phonological error score

2. Damage was measured by the

reversal rates


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The improvements came about because the

simulations implement both pathways of the

triangle model in order to explain semantic

effects on reading.

People with dementia find exception words

difficult to pronounce and repeat if they

have lost the meaning of words.


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Patterson and Hodges: the integrity of lexicalrepresentations depends on their interactionwith the semantic system: semanticrepresentations bind phonological

representations together with a semanticglue

-semantic glue hypothesis

a semantic system gradually dissolves indementia, so the semantic glue is graduallyreleased and the lexical representations losetheir integrity.


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Patients are therefore forced to rely on a

sublexical or grapheme-phoneme

correspondence reading route leading to

surface dyslexic errors.

Furthermore, they have difficulty in

repeating irregular words for which they

have lost the meaning, but they can repeatlists of words for which the meaning is

intact.


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PMSP showed that a realistic model of

surface dyslexia depends on involving

semantics in reading.

In surface dyslexia, the semantic pathway is

damaged, and the isolated phonological

pathway reveals itself as surface dyslexia.


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Plaut: some patients have substantial

semantic impairments but can read words

accurately

-there are differences in the division oflabor between semantic and phonological

pathways

The revised model takes into account

individual differences between speakers, andshows how small differences in reading

strategies can lead to different consequences

after brain damage.


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Phonological dyslexia arises by impairments

to representations at the phonological level,

rather than to grapheme-phoneme

conversion.

-phonological impairment hypothesis

People with phonological dyslexia can still

read because their weakened phonologicalrepresentations can be accessed through the

semantic level.


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Problem: it is not clear that it would

correctly handle the way in which people

with phonological dyslexia read

pseudohomophones better than other types

of nonwords.

There have also been effects of orthographic

complexity and visual similarity, suggesting

that there is also an orthographic impairmentpresent in phonological dyslexia.


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Howard and Best: Melanie-Jane

gerl

Phocks

There was no effect of visual similarity for

nonwords but Harm and Seidenberg show

that a phonological impairment in a

connectionist model can give rise to sucheffects.


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This model was trained by back-propagation

to associate word pronunciations of a

representation of the meaning of words.

It shows that one type of lesion can give riseto all the symptoms of deep dyslexia

particularly both paralexias and visual errors.

The model was trained to produce an

appropriate output representation given aparticular orthographic input using back-

propagation.


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Lesions resulted in four types of error:

1. Semantic (where an input gave an output

that was semantically but not visually

close to the target)2. Visual (visually but not semantically close

to the target)

3. Mixed (both semantically and visually

close to the target)4. others


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Hinton and Shallice:1. Provides an explicit mechanism whereby

the characteristic can be derived from amodel of normal reading.

2. Shows that the actual site of the lesion isnot primarily important.

3. Shows why symptoms that were previouslyconsidered to be conceptually distinct

necessarily co-occur.4. Revives the importance of syndromes as

neuropsychological concept.


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Plaut & Shallice: the semantic

representations of abstract words contain

fewer semantic features than those of

concrete words; that is the more concrete

the word is, the richer its semantic

representation.


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Simple dual-route model providesan inadequate account of reading,and needs at least an additional

sematic route through imageablesemantics.

Analogy models have someattractive features but theirdetailed workings are vague andthey do not seem able to accountfor all the data.


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Connectionist modelling hasprovided an explicit, single-routethat covers most of the main

findings, but has its problems.It has set the challenge that only

one route is necessary in readingwords and nonwords and thatregularity effects in pronunciationarise out of statistical regularitiesin the words of the language.


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At present, these models are in

relatively early stage of

development, and that it would

be premature to dismiss them

because they cannot yet account

for all the data.


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Thank you!

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7-Models of Word Naming