Title: Genetics of Language
1Genetics of Language Language Disorders
- Karin Stromswold
- Dept. of Psychology Center for Cognitive
Science - Rutgers University - New Brunswick
- Portions of this work were supported by
- Johnson Johnson Foundation
- John Merck Foundation
- Charles Johanna Busch Biomedical Research
Grant - Bamford-Lahey Childrens Foundation
- National Science Foundation (BCS-9875168,
BCS-0042561, BCS-0124095) - Correspondence may be sent to
karin_at_ruccs.rutgers.edu
2Key Questions
- Do genetic factors affect peoples ability to
acquire and use language? - Do these factors affect 'normal' peoples
linguistic abilities or just those with language
disorders? - Do language-specific genes exist?
- Are genetic factors involved in all aspects of
language? - Are the same genetic factors involved in all
aspects of language? - How do genes/environment interact?
3Content
- Relationship between innateness heritability
- Review/meta-analysis of genetic studies of
language - Family aggregation studies
- Pedigree studies
- Adoption studies
- Twin studies
- Linkage studies
- Limitations/Worries
- Conclusions
4Innateness Hypothesis Heritability
- Typical evidence Universal, learnable, modular
- Genetic evidence If innate cognitive
predisposition or neural structures enable us to
use/acquire language, they must be encoded in our
DNA - Why we might fail to find evidence for language
heritability - Heritability amount of individual variation due
to genetic factors - The Innateness Hypothesis is wrong
- Linguistically-speaking, (normal) people are
genetically identical Chomsky (1980)
Language is like number of fingers Lieberman
(1984) Language is like height
5Innateness Hypothesis Heritability
- Individual differences may exist
- Acquisition rate for vocabulary (e.g., Goldfield
Reznick, 1990), morphology (e.g., deVilliers
deVilliers, 1973), syntax (e.g., Stromswold 1990,
1995, Snyder Stromswold 1997).. - Adult linguistic proficiency verbal fluency
(e.g., Day, 1979), compound nouns (e.g., Gleitman
Gleitman, 1970), sentence processing (e.g.,
Corely Corley, 1995 Bever et al., 1989),
second language acquisition (e.g., Fillmore,
1979), grammaticality judgments (e.g., Ross,
1979 Nagatu, 1992 Cowart, 1994). - Caveat Genetic factors could account for
differences among abnormal populations but not
normal populations - The case with number of fingers genetic
syndromes associated with too many/few fingers - (Contrast with heritability of finger length)
6Methodology
- The power of meta-analyses
- Increase statistical power
- Methodological weaknesses of individual studies
less worrisome - Searched PsycINFO, ERIC, Medline databases for
- language, linguistic, articul, speech, read or
spell AND - hereditary, genetic, famil, twin, adoption,
chromosom, linkage, pedigree, sex-ratio,
segregation, aggregation, DNA, or RNA - Excluded language disorders that were acquired,
progressive, syndromic, or secondary to hearing
loss, mental retardation, psychiatric/neurological
disorder etc.
7Family Aggregation of Spoken Disorders
- Do language disorders aggregate (cluster) in
families? - Yes Meta-analyses of 18 studies revealed
- SLI probands are more likely to have a positive
family history 46 (range 24-78) vs. 18
(range 3-46) - SLI probands have more impaired relatives than do
controls 28 (range 20-42) vs. 9 (range
3-19) - Caveat Difficult to separate the role of genes
vs. environment (Deviant Linguistic Environment
Hypothesis)
8DLEH Predictions are not Borne Out
- Language impairments sometimes skip generations
- Most severely impaired children dont come from
families with highest incidence of impairment - Parents who speak normally (but have history of
language delay) are more likely to have
language-impaired children - Even in families with very high impairment rates,
some family members are normal - In most families, some siblings are impaired and
others are not - No relationship between birth order and
probability of impairment - Concordance is no greater between primary care
provider and child other first degree relatives - Language-impaired children dont always have the
same impairment as their relatives
9Pedigree Studies Modes of Transmission
- Autosomal Dominant (AD) Most probands will have
1 impaired parent, and half of siblings will be
impaired - Autosomal Recessive (AR) Most probands will
have 2 unaffected parents, and one quarter of
siblings will be affected - X-linked Recessive (XLR) Impaired males have 1
bad gene, impaired females have two bad genes.
Thus, the MF is nn2 (where n is the frequency
of the disordered allelle) - Most genetic language disorders arent SML.
Review of lit shows - One-third of probands have 1 affected parent
Genetic heterogeneity or AD with high rate of
spontaneous mutation, or incomplete penetrance or
expressivity - One-quarter of probands have 2 affected parents
High assortative mating, very high incidence of
language disorders, SML models are wrong - One-third of siblings are impaired Either AR or
genetically heterogeneous - Sex ratios generally between 21 to 31. Even
most extreme only 61 Not XLR
10Colorado Adoption Project (CAP)
- Rationale If genes are important for a trait,
adopted childrens abilities will resemble their
biological relativesabilities. If environment
is important, adopted children will resemble
their adopted relatives. - Design Large (Ngt300) longitudinal study that
compares adopted and nonadopted childrens skills
with those of their biological and adopted
parents and siblings. - Language Disorders (Felsenfeld Plomin, 1997)
156 children at age 7 - Positive biological family history was the best
predictor of language disorders - 25 of children with biological family history
were impaired (9 with adopted FH) - Sibling comparisons at age 7 (Cardon et al.,
1992) - Vocab verbal fluency h .90 (IQ-related .46,
Language-specific .83) - Fluency only h .33 (IQ-related .54,
Language-specific .20) - Vocab only h .47 (IQ-related .69,
Language-specific .00)
11CAP Parent-Child Comparison (Plomin et al., 1997)
Verbal Abilities
Spatial Abilities
Processing Speed
Recognition Memory
12CAP Conclusions
- Heritable factors affect verbal abilities more
than other types of abilities - The influence of genetic factors becomes more
apparent with age - Specific-to-language factors are only seen at age
7 (but this may be because overall IQ was used). - Caveats about adoption studies
- All studies from a single group of children (what
if not representative) - Verbal assortative mating was greater for
adoptive parents than biological parents This
probably lowered heritability estimates - Selective adoptive placement was not a problem
(low correlation between adoptive and biological
mothers verbal skills)
13Twin Study Rationale
- Rationale Identical (monozygotic, MZ) and
non-identical (dizygotic, DZ) twin pairs share
the same environment, but MZ cotwins share 100
of their DNA, whereas DZ twins share 50 of their
DNA - Therefore If MZ cotwins are more similar
linguistically than DZ twins, this suggests that
genetics plays a role in language. - Can quantify the relative role of genetics and
environment by measuring how much more similar MZ
twins are than DZ twins.
14Concordance Rates for Twin Pairs
- Are concordance rates for MZ gt DZ twins?
- Number of Impaired Individuals in Concordant
Pairs - Total Number of Impaired Individuals
- Two types of meta-analyses
- Mean rates Treat each studies MZ DZ
concordance rates as data points, and use sign-
and t-tests to determine if there is a
significant difference. - Overall rates Pool data from all studies and
calculate overall concordance rates. Use
Z-scores to test if MZ-DZ rates are different
15Twin Correlational Analyses
- Are MZ twins test scores more highly correlated
than DZ twins? - Phenotypic variance variation for a trait in a
population - Heritable factors Falconers h2 2rMZ - rDZ
- Common environment factors c2 rMZ - h2
- Non-shared environmental factors e2 1 - rMZ
- Unweighted meta-analysis rMZ and rDZ are data
points - Weighted meta-analysis Weighted mean Fishers
zs for MZ and DZ twins were calculated and
compared using Z-scores
16Other Genetic Analyses
- DeFries-Fulker Extreme Analysis When impaired
people are ascertained by deviant scores,
cotwins scores on the same test will regress
toward the mean score of an unselected
population. If genes play a role, DZ cotwins
scores will regress more than MZ cotwins. - Generalized DF Analysis extension for
unselected populations - If heritability estimate for language-impaired
twins (h2g) is greater than for general
population (h2), this indicates that certain
genes contribute to the linguistic variance
observed among language disordered people, but
not for the variance in the general population - Bivariate heritability Twins performance on
test A is compared with that of his cotwin on
test B. If rMZ is greater than rDZ, the
phenotypic similarity on two tests is the result
of genetic factors (but maybe not the same
genetic factors) - Genetic correlation (rG) Do the same genetic
factors affect A and B?
17MZ Concordance Rates are Higher
- Spoken language disorders 5 studies (266 MZ,
161 DZ pairs) - Mean 84 for MZ, 52 for DZ, p lt .0001
- Overall 84 for MZ, 48 for DZ, p lt .0001
- Written language disorders 5 studies (212 MZ,
199 DZ pairs) - Mean 76 for MZ, 41 for DZ, p lt .01
- Overall 75 for MZ, 43 for DZ, p lt .0001
- Combined spoken/written disorders (478 MZ, 360 DZ
pairs) - Mean 80 for MZ, 46 for DZ, p lt .0001
- Overall 80 for MZ, 46 for DZ, p lt .0001
- But why arent MZ concordance rates 100? Three
possibilities - MZ twins arent identical genetically and/or
environmentally - Expressivity of language disorders is incomplete
- Failure to diagnose language disorders in some MZ
cotwins - DZ pair-wise concordance rate (26) is similar
to non-twin siblings (30)
18Spoken Language Disorders
19Written Language Disorders
20SLI Twins Test Performance
- Bishop et al (1995) 63 MZ, 27 DZ twin pairs
- Articulation Falconers h2 1.82
- Phonological STM DF h2g 1.25
- Receptive vocabulary DF h2g 1.35
- Morphosyntax Wechsler h2g 1.10, CELF h2g
.56, TROG h2g 1.09 - (But when nonverbal IQ partialled out, no
significant genetic effects) - Bishop et al (1999)
- 27 MZ, 21 DZ Pure tone sequence repetition DF
h2g .11 - 25 MZ, 22 DZ Nonword repetition DF h2g 1.17
- Tomblin Buckwalters (1998) data minus triplets
(58 twins) - Falconers h2 .66, p .05
- Bivariate heritability for nonverbal IQ
language .21 - Genetic correlation, RG .01 (ie., different
genetic factors influence verbal nonverbal
disability)
21TEDS Twins Test Performance
- TEDS study Large population-based, parent
report twin study - Dale et al (1998) Analyzed data for twins with
the smallest vocabularies (bottom 5tile, 135
twin pairs). DF h2g .73 (vs. h2 .25 for all
TEDS twins) - Eley et al. (1999) DF h2g greater for TED twins
with small vocabularies than twins with normal
vocabularies. - Eley et al. (2001) genetic continuity is
greater for small vocab probands than other
proband groups - Purcell et al. (2001) Are the genetic factors
specific to vocabulary? - When probands were selected based on small
vocabularies, RG for low verbal nonverbal
scores 1.0 (i.e., the genetic factors that
cause 2 years olds to have small vocabularies are
the same as those that cause them to have
nonverbal delays.) - When probands were selected based on poor
nonverbal scores, the vocabulary-nonverbal RG
.36 - Why the asymmetry Differences in homogeneity of
the samples? Problems with the measure?
Directionality of effect?
22Colorado Twin Study of Reading Disability
- Olson et al (1989) Genetic factors played a
large role for phonological reading (DF h2g
.93) but not orthographic reading (DF h2g
.-.16). - Light et al. (1998). DF h2g for phonological
reading .52 overall reading .70 - Castles et al (1999) Genetic factors account for
twice as much of the variance in phonological
dyslexics as orthographic dyslexic (67 vs. 31) - Gayan Olson (1999) contra Castles et al.
(1999) argue that heritable factors play a
significant role in all types of dyslexia. - Olson et al. (1999) Wadsworth et al. (2000)
genetic factors play a greater role in reading
disability among children with high IQs than low
IQs - Light et al. (1998) RG for overall reading/math
.36 (60 due to genetic factors common with IQ
and 20 due to genetic factors common to
phonological reading)
23Summary Twin Language Disorders
- Some language disorders are genetically based
(25-100) - Genetic factors probably affect the linguistic
abilities of disordered populations more than the
general public (75 vs. 25) - Genetic language disorders seem to impact
different aspects of language, but less is known
about phonology, morphology syntax - Unknown if the same genetic factors cause
different types of language disorders (and even
if they do, what would this mean?) - Unclear if the genetic factors identified are
specific to language - The few existing studies have conflicting
results, possibly reflecting aspects of language
assessed, methods of assessing etc.
24Normal Twin Vocabulary Studies
- Overall 8 studies with 1577 MZ, 1389 DZ twins
- Unweighted mean rMZ .81, rDZ .57,
Falconers h2 .48 (p .002) - Weighted mean rMZ .93, rDZ .76, Falconers
h2 .33 (p lt .0001) - Early 3 studies with 1247 MZ, 1152 DZ twins
18-24 months old - Unweighted mean rMZ .91, rDZ .78,
Falconers h2 .26 (p .08) - Weighted mean rMZ .95, rDZ .80, Falconers
h2 .29 (p lt .0001) - Late 5 studies with 330 MZ, 237 DZ twins 3-13
years old - Unweighted mean rMZ .75, rDZ .44,
Falconers h2 .62 (p .001) - Weighted mean rMZ .71, rDZ .45, Falconers
h2 .53 (p .02) - Role of genes increases with age (2 long. studies
meta-analysis) - Unclear whether genes are specific to language (1
study yes, 1 study no, 1 longitudinal study
yielded different results at different ages) - Different genes affect normal impaired twins
vocabulary - Bottom 5tile TEDS complete genetic overlap for
vocab nonverbal skills. - For all TEDS twins, vocabulary-specific genetic
factors exist
25Normal Twin Vocabulary Studies
26Normal Twin Phonology/Articulation
- Phoneme Discrimation 21 pairs of 2-3 year olds
(Fischer 1973) - rMZ .64, rDZ .53, Falconers h2 .22 (p gt
.10) - Phonemic Awareness 126 pairs of 6-7 year olds
(Hohnen Stevenson 1999) - Weighted mean rMZ .90, rDZ .56, Falconers
h2 .68 (p lt .001) - Age 6 29 IQ-related genetic factors, 23
vocab/morphosyntax, 9 phonology - Age 7 18 IQ-related genetic factors, 67
vocab/morphosyntax-related - Phonological STM 100 pairs of 7-13 year old
twins (Bishop et al. 1999) - Heritable factors do not affect the ability to
repeat sequences of pure tones - Heritable factors do affect the ability to repeat
nonsense words (h2 .71, p .01) - Articulation 180 pairs of 3-8 yrs (Matheny
Bruggemann 73, Mather Black 84) - Weighted mean rMZ .93, rDZ .79, Falconers
h2 .26 (p .03)
27Normal Twin Phonology Articulation
28Normal Twin Morphosyntax
- 12 twin studies of children between 20 months
12 years. - Diversity of methods used and aspects of
morphosyntax assessed precludes combining data
from these studies, but - rMZ significantly greater than rDZ for all
measures in 5 studies, 2/3s of measures in 1
study, and 1/2 of measures in 2 studies. In 4
studies, MZ-DZ differences were not significant
in majority of measures - rMZ gt rDZ in 33 of 36 measures, p lt .0001
- Mean rMZ gt rDZ for each of 12 studies, p lt .0001
- Significant differences were more common in
larger studies and in studies that used cleaner
measures of morphosyntax - Do language-specific genes exist?
- Munsinger Douglass (1976) MZ-DZ difference
significant even when nonverbal IQ partialled out - Hohnen Stevenson (1999) Syntax-specific genes
account for 20-30 - Dale et al. (1999) Genetic factors are specific
to language but not syntax (however,
parent-report syntax measure is worrisome) - No evidence that influence of genetics increases
with age
29Normal Twin Morphosyntax
30Normal Twin Written Language
- Reading 5 studies with 745 twin pairs
- Weighted mean rMZ .86, rDZ .66, Falconers h2
.45, p .002 - Hohnen Stevenson (1999) Some genetic factors
are specific to language but not reading
(20-30), with a modest amount specific to
reading (20-30). Genetic factors common to IQ
have only a modest effect (10), and genetic
factors specific to phonemic awareness have no
effect on normal childrens reading (c.f.,
dyslexia findings) - Spelling 2 studies with 246 twin pairs (Osborne
et al, 1968 Stevenson et al, 1987) - Weighted mean rMZ .78, rDZ .48, Falconers h2
.60, p .002 - Stevenson et al. (1987) Heritabilty estimates
are greater for IQ-adjusted scores than
non-adjusted scores (.73 vs. .53)
31Normal Twin Reading
32Summary of Twin Results
- Genetic factors play a greater role for
language-impaired people (1/2 -2/3) than
normals(1/4-1/2) - Genetic factors affect all aspects of language
- Probable existence of some language-specific
genes - Possible existence of some genes specific to
different aspects of language
33Potential Worries With Twin Studies
- Gene/environment interactions the
generalizability of heritability estimates
obtained from twins - Twins have higher rates of impairments/delays
than singletons - Twins have impoverished prenatal postnatal
environments - Environmental assumptions
- Prenatal Do MZ and DZ twin pairs have the same
prenatal environment? - Postnatal Do MZ and DZ twin pairs have the same
postnatal environment? - gt Swedish Separated-at-Birth Twin Study
(Pedersen et al 1994) yielded similar
heritability estimates for reared apart twins as
is found for reared together twins - Genetic assumptions
- Are MZ twins genetically identical?
- Are DZ twins genetically equivalent to siblings?
34Linkage Studies Background
- Naming conventions
- Humans have 22 pairs of autosomal 2 sex (Y, X)
chromosomes - Autosomal chromosomes are numbered from 1-22 by
size (1 is largest) - Each chromosome has a constriction short arm
(p) long arm (q) - Thus, 15q21 refers to staining band 21 on long
arm of chromosome 15 - Multiplex analyses Compare DNA of affected and
unaffected family members in highly affected SML
transmission families. Do marker locus and trait
locus assort independently or is there decreased
recombination (indicating 2 loci are neighbors)?
Logarithm of odds score gt 3 indicates linkage.
LOD of -2 indicates no linkage. Problem
multiplex analyses reveal genes that can cause
SLI, but rarely do - Sibling pair analyses Compare DNA of affected
and unaffected siblings. If a trait locus is
closely linked to a marker locus, similarity
between siblings for the marker alleles should
correspond with phenotypic similarity, regardless
of the mode of transmission (i.e., works with
non-SML disorders)
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36The KE Family
KE family Multiplex family with AD disorder
that includes grammatical deficits (Gopnik
1990), oral dyspraxia (Fisher et al. 1998, Hurst
et al. 1990), and low nonverbal IQ and nonverbal
learning disorders (Vargha-Khadem et al. 1995)
377q31 Loci for Spoken Impairments
- Fisher et al. (1998) Disorder in KE family is
linked to 7q31 - Tomblin et al. (1998) Linkage of SLI with 7q31
in a population-based study of second graders - Lai et al. (2000) The disorder is linked to
7q31.2 in affected KE family members and an
unrelated person with a similar disorder - Lai et al (2001) All and only affected family
KE members have an abnormal form of the FOXP2
gene. The gene codes for transcription factor,
and is highly expressed in fetal tissue and its
homologue is found in mouse cerebral cortex. - Enard et al. (2002) The FOXP2 homologue in
non-human primates (and mouse) differs from that
of humans. - Genetic link between 7q31 and Tourette Syndrome
and autism
38Other Loci for Spoken Impairments
- Froster et al. (1993) Family with 1p22 and 2q31
translocation associated with written spoken
impairments - Elcioglu et al. (1997) Isolated case of severe
language delay but normal nonverbal abilities
Inverted duplication of 15q13-gt15q2. - Bartlett et al. (2000) 19 multiplex families
with linkage near 4 dyslexia loci (1p36, 2p15,
6p21, 15q21). No linkage to 7q31 - Cholfin et al. (2000) Multiplex family with AD
transmission, but no linkage to 7q31 - SLI consortium (2002) 98 siblings. 16q24
(nonword rep), 19q13 - Bartlett et al. (2002) 5 Canadian multiplex
families 13q21
39Going from Loci to Genes
- SLI Lai et al. (2001) FOXP2 transcription
factor gene. - Dyslexia possible candidate genes
- 1p34-p36
- 2p15-p16 phosphotase calcineuron (psychiatric
disorders) - 6p21-p23 HLA (autoimmune), GABA-beta receptor 1
(CNS inhibitor), lyso-phospholipid coenzyme A
acyl transferase (fatty acid and membrane
phospholipid metabolism gene), human kinesin gene
(C elegans mutant have behavioral disorders) . - 6q13-16.2
- 15q21-q23 beta2-microglobin gene (autoimmune)
neuronal tropomodulin 2 3 (a major binding
protein to brain tropomyosin) - 11p15.5 dopamine D4 receptor gene
40What we dont know . Phonology
- Do genetic factors affect phonology (vs.
articulation)? - Stromswold Ganger (in prep) analysis of
monthly spontaneous speech samples (22-47 mo)
from 8 sets of normal twins - Size of phonetic inventory is not more similar
for MZ cotwins - Order of acquisition of phonemes is more similar
for MZ cotwins - Accuracy rate is more similar for MZ cotwins
- Syllable initial 7.7 vs. 16.4
- Syllable final 9.9 vs. 15.9
- Patterns of errors may be more similar for MZ
cotwins - Substitution rates similar, but MZ cotwins more
likely to make the same substitutions - MZ cotwins more likely to make the same classes
of substitution errors (e.g., fronting, voicing
errors, stopping) - Deletion rates more similar for MZ than DZ
cotwins
41What we dont know . Syntax
- To what extent do genetic factors play a role in
syntax? - Published syntax studies generally are small
and/or use worrisome measures - To do large-scale studies, we need a syntax test
that parents can administer - The Parent Assessment of Language (PAL)
- Weve designed and are norming a series of
parent-administered test for children ages 3 and
above. Each years PAL tests childrens
comprehension of syntactic constructions that
children are mastering at that age (actives,
passives, reflexive, pronouns, relative
clauses,modals, subjunctives, subject and object
control structures, etc.). - Longitudinal twin study using the PAL (current N
120)
42PAL Syntax Items (Picture-pointing)
- Age 3 Age 4
- 4 Full Actives The bear licked the dog 4 Full
Passives The bear was licked by the dog - 2 Easy Reflexives The bear licked himself 2
Easy Pronouns The bear licked him - Age 5 Age 6
- 1 Full Active The bear was licking the dog 1
Truncated Active The bear was licking - 3 Full Passives The bear was licked by the
dog 3 Truncated Passives The bear was licked - 2 Easy Reflexives The bear was licking
himself 2 Easy Pronouns The bear was licking
him - Ages 7 8
- 1 Full Active The bear was licking the dog 1
Truncated Active The bear was licking - 3 Full Passives The bear was licked by the
dog 3 Truncated Passives The bear was licked - 1 Easy Reflexives The bear was licking
himself 1 Med Reflexive The dog's friend was
licking himself - 1 Easy Pronoun The bear was licking him 1 Med
Pronoun The dog's friend was licking him - Ages 9 10
- 1 Full Active The bear was licking the dog 1
Truncated Active The bear was licking - 3 Full Passives The bear was licked by the
dog 3 Truncated Passives The bear was licked - 1 Med Refl. The dog's friend was licking
himself 1 Hard Refl The friend of the dog was
licking himself - 1 Med Pronoun The dog's friend was licking
him 1 Hard Pronoun The friend of the dog was
licking him - Age 11 and above
- All preceded by One of these two dogs is hot and
followed by the query Which dog is hot?
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49PAL Syntax Yes/No/Maybe Task (Ages 9)
- Sally said Shouldnt you make the knot tight?
Did Sally think the knot should be tight? - Billy wont go to the park unless John goes.
Will Billy stay home? - Katie promised Lucy, who was thirsty, to buy
juice. Did Lucy say she would buy juice? - Mary who is going to the party with Steve does
not like to dance. Does Mary enjoy dancing? - Michaels cat chased the mouse and ran away.
Did Michaels cat run away? - Jim thinks Tom is bad at sports. Is Tom bad at
sports? - Maybe the band would have played last night if
the drummer hadnt quit. Did the band play last
night? - The doctor who was looking for the nurse walked
home from the hospital. Did the doctor walk
home from the hospital?
50What we dont know . Specificity
- Do language-specific genes exist?
- Need more, large studies that assess development
in many different areas (not just cognitive
abilities, but also fine motor, gross motor, oral
motor, social etc.) - Do specific genes for different aspects of
language exist? (e.g., syntax-specific,
phonology-specific, lexicon-specific) - Need to assess multiple aspects of language in a
large group of children - Data that we are collecting in our twin study
- PAL assesses articulation, lexical access,
reading/pre-reading, and syntax - ASQ parent assessment of gross motor, fine
motor, cognitive, language social-emotional
skills - Developmental milestones (gross motor, fine
motor, cognitive, language, social) - Special educational/therapy services
- Neuropsychological diagnoses
51Sample PAL (Age 4)
Articulation of onsets
List any sounds the child regularly says wrong,
and give a typical mispronounced word
Lexicon Rapid naming (number of foods named in
30 seconds) Pre-reading Capital letter
identification. (Orthographic and phonologic
word reading starting at age 6 PAL.) Syntax
Picture pointing comprehension task 4 actives
(e.g., the dog licked the bear) 4 passives
(e.g., the fox was tickled by the lion) 2
reflexives (e.g., the cat scratched himself) 2
pronouns (e.g., the monkey splashed him)
52What we dont know Gene x Environment
- Koeppen-Schomerus et al. (2000) Heritable
factors play a negligible role in linguistic and
cognitive abilities of very premature TEDS twins.
- What is the relative importance of prenatal and
postnatal environment? - We are comparing heritability estimates for twins
with easy/hard prenatal courses - Gestational age
- Birthweight
- Birthweight percentile
- Brain injuries
- Short (discharged before or by due date ) vs.
long hospital stays - Composite neonatal morbidity measure
- We are comparing heritability estimates for twins
with different postnatal environments (SES,
therapeutic interventions, traditional vs.
developmental NICUs) - Are there specific perinatal factors that place
twins at risk (e.g., steroids, MgSO4,
intrauterine infection, placental infarction,
ventilation, TTTS, etc.)? - Quantifying the role of prenatal environment we
are comparing outcomes for MZ twins with very
similar birth weights and very different birth
weights (MZS -MZD ) and DZ twins with
similar/different birth weights
53What we dont know Going from genes to disorders
- The genotype to phenotype mapping problem
- One GenotypeMany Phenotypes / One PhenotypeMany
Genotypes - The developmental problem phenotypes change
- Direct vs. indirect genetic effects The case of
clotting disorders - Indirect If a mother has a genetic clotting
disorder, her children are at risk even if they
not carry the mutation. - Direct A child with a genetic clotting disorder
is at risk for perinatal strokes (and the
language areas of the brain are particularly
vulnerable) - Maternal/child interactions possible when both
have the disorder - Environmental interactions high estrogen, low
folic acid, delayed child-bearing - Specificity problem
- Familial Dysautonomia (9q31 IKBKAP). AR
disorder with normal IQs and profound oral motor
dyspraxia (but they also have ANS problems) - FOXP2 Do people with 7q31-linked autism and
Tourette Syndrome have the FOXP2 mutation? - Just so stories
54What if Language is Like Height?
- Quantative Trait Loci (QTLs) Multifactorial-polyg
enic -
- Hypothesis In normal people (and in most
language-impaired people), variance in linguistic
ability results from many genes (each of which
has a small effect) acting together and in
combination with the environment. Thus,
linguistic abilities are normally distributed,
and the observed heritability is due to QTLs - How to find language QTLs
- People practice linguistic assortative mating.
- Assortative mating increases genetic variance in
successive generations - Assortative mating additive genetic variances
makes QTLs easier to find - It is easier to detect QTLs by looking at the
high end of the distribution (at the low end,
random mutations environmental insults obscure
QTL effects) - Linguists (particularly second generation
linguists) should donate their DNA
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