Theoretical Perspectives onSLI

LING419_13NOV08

What exactly is wrong withchildren with SLI?

• What we know:– Neurodevelopmental disorder– Multi-gene source– Morphosyntax affected crosslinguistically

• What we need to find out:– Deficits in processing or representation?– Deficits domain general or domain

specific?

Morphological richness/typological characteristics of language

Surface hypothesis

RDDR (representational deficitsfor dependent relations)

Generalized slowing hypothesis

Missing agreement hypothesisPhonological/short term workingmemory deficits

Extended Optional Infinitive/Disruption-within-delay

Limited information processingcapacity

Representational theoriesProcessing theories

Cognitive/linguistic limitationsin in SLI

• Linguistic vs. cognitive deficits in SLI– Low normal IQ

• Kirchner & Klatsky (1985): familiar wordrecall

Cognitive/linguistic limitationsin in SLI

• Bishop (1992): Information gap– number of attributes to remember in describing– Array: 1 = girl riding red bike with little wheels; 2 =

boy rising a red bike with little wheels; 3 = boy ridingyellow bike with big wheels; 4 = boy riding yellowbike with little wheels

– Target = boy riding red bike with little wheels

• Haptic recognition tasks: remembering a shapethat was touched to select a picture of it

Limited Information ProcessingCapacity

• Domain general account• Fast mapping, word retrieval problems (GAP

verbs), use of grammatical morphemes - all asingle cause?

• Passive sentences reconsidered: morphology orparsing?“The girl is kissed by the boy”

• Paradox/problems with limited informationprocessing accounts

Phonological/ST WorkingMemory

• More focused than limited informationprocessing, but still domain general

• Short term working memory (STWM):• STWM and vocabulary skills in TD

children linked until age 8• Children with SLI do poorly on non-word

repetition tasks (graph)

Gathercole & Baddeley (1990)

Phonological/ST WorkingMemory

• Deficits in non-word repetition are highlyheritable– MZ and DZ twins

• How do deficits in STWM causelanguage outcomes in SLI?

Generalized SlowingHypothesis

• Focused version of limited informationprocessing and domain general

• Kail (1994): RTs on tasks– Picture naming task components:

a. Recognition of pictureb. Retrieval of concept/namec. Phonological formulationd. Articulation

RTTD = a + b + c….RTSLI = m(a + b + c…)SLI RTs about 33% slower

Miller et al. (2001)

• Purpose: Test GSH• Participants: 29 CA-TD and 29 SLI;

matched for non-verbal IQ (mean = 99)• Procedures: measured RT on cognitive

and linguistic tasks

Task Type Description

Motor

Tapping tap one or two keys as quickly as possible

Simple RT strike a key in response to ***

Nonverbal Cognitive

Visual search strike a key if target shape is

present in an array, another if

absent

Mental rotation strike one key if 2nd shape

matches the target, strike another

key if it is the mirror image of the

target

Lexical

Picture matching strike one key if two pictures

match on criterion, another key if

they don’t match. Criterion =

categories like vehicles, animals, etc.

Picture naming speak the name of the picture

shown

Grammatical

Truth value strike on key if picture matches

sentence heard, another if not

Grammaticality judgement strike on key is sentence heard is

correct, another if it is not

Phonological

Judge rhymes strike one key if stimuli rhyme,

another if not

Judge initial consonants strike one key if stimuli start with

the same sound, another if not

Miller et al. (2001)

• Results: SLI longer RTs for all tasks(14% - 21%)

• Conclusions:• Proposed impact on language learning:

• What GSH doesn’t really explain:

Slower processing & languageoutcomes

• Lahey et al. (2001): is speed ofprocessing related to severity ofimpairment?– 66 SLI, standardized test battery scores &

RTs from processing tasks• Montgomery & Windsor (2007): Do

STWM & RTs predict standardizedtest scores in SLI?

Surface Hypothesis• Focused, but domain general• Children with SLI have

auditory/phonological processing deficits• Linguistic input more difficult to intake:

– Short duration– Unstressed syllables– Non-salient position (medial)

Surface HypothesisCrosslinguistically

• English:– Consonantal suffixes = short duration– BE morphemes often contracted– Verb stems and verb-ing = more salient

• Italian and Hebrew:– Grammatical morphemes often

vocalic/syllabic– Free standing morphemes often non-

salient, medial position & unstressed

Combining GSH & Surface

• In addition to phonetic substance:– Frequency– Regularity of distribution– Transparency (of morphemes)

• Additive effects of all factors =difficulties for intake of linguistic input

• Combination used to deviance profiles

If inflected words were typically heard in one-word sentencesseparated by pauses, there would be no problem. However,fast on the heels of the inflected word is the next word in theutterance that must be held in working memory andprocessed, and so on. Thus, processing is pressed from twodirections; processing of a first item must be completed beforethe item fades from memory, and it must be processed in timefor the next item. Given the reduced speed of processingassumed for children with SLI, sufficient processing of oneitem can’t be completed before the next item appears.Consequently, some material is processed incompletely or notat all. In a language like English, it is reasonable to expect thatif an inflected word is incompletely processed, only the barestem will be retained. Leonard (1998), p. 251

Example of morphologicallearning with Italian

NUMBER

singular plural

1st bevo beviamo

2nd bevi bevete

PERSON

3rd beve bevono

NUMBER

singular plural

1st -o -iamo

2nd -i -ete

PERSON

3rd -e -ono

Morphological learning

• From word-specific to paradigm-general

• Inflected words initially acquired aswholes, with semantics: “bevo” I drink– Inflected separated later: bev-o

• Frequent stem+suffix learned earlier– /-ete/ learned last

Morphological learning

• Productive paradigm building takesplace on two intersecting planes:– Vertical comparisons: bevo, bevi, beve -->

/bev-/– Horizontal comparisons: bevo, verb2o,

verb3o --> /-o/ = 1st pers

Source of breakdown in childrenwith SLI

• Children with SLI need more encounters withmorphemes

• Children with SLI extra sensitive to infrequentforms in paradigm

• Children with SLI will make omission andsubstitution errors

• GSH+ Surface = deficits in intake mainly;additive effects

Problems with SurfaceAccount

• Short duration = harder to process:Contradiction in logic?

• No categorical definition of “low phoneticsubstance”

• Plural “s” and third person singular “s”• Can’t explain difficulties in syntactic operations

like wh-movement, SAI, interpretation of relativeclauses without assumption of limitedinformation processing

Processing accounts andmorphological richness

• Trade off in resources = explanation• Trade off = focus on what is important

to meaning• More is better but only up to a point…

– Too much juggling at intake• But, trade off in processing resources?

Or, in resources used to establish rulesand representations?