Title: Early speech
1Early speech language skills etiological links
to reading
- Emma Hayiou-Thomas
- Department of Psychology
- University of York
2Language Reading
- Enormous body of research linking phonological
skills reading - Especially decoding
- Less clear how non-phonological language skills
are related to reading - More important for comprehension
3Quadrant model of SLI dyslexiaBishop
Snowling, 2004
4Behavioural genetics Phonology reading
- Phonological awareness reading
- Colorado twin study, rg .70
- Gayan Olson, 2001
- Phonological STM reading
- Reading problems more heritable in combination
with nonword repetition deficits - Bishop, 2001 Bishop, Adams Norbury, 2004
5Behavioural genetics Phonology reading
- Longitudinal evidence
- Phonological awareness in preschool has
substantial genetic influence - Stable through kindergarten
- Generalises to kindergarten reading
- Byrne et al., 2005 Byrne et al, 2006
6Behavioural genetics Broader oral language
reading
- Language, IQ, phonological awareness, and reading
(6-7 years) - Covariance genetically mediated
- Hohnen Stevenson, 1999
- Semantics, syntax, phon awareness, rapid naming,
letter knowledge (preschool) - Both genetic and (shared) environmental
covariance - All influences on oral language also influenced
literacy measures - Additional genetic and environmental influences
specific to literacy variables - Samuelsson et al., in press
7Study aims
- Phenotypic associations between oral language
reading skills - Phonology ? Decoding
- Semantics/Syntax ? Reading comprehension
- Etiology of the associations
- Genetic link for phonology decoding
- Genetic AND shared environmental link for
semantics/syntax reading comprehension
8Twins Early Development Study
- Based at the Social, Genetic, Developmental
Psychiatry Centre (SGDP) Institute of
Psychiatry - Sampling frame all twins born in England and
Wales in 1994, 1995 1996 (15,000 twin pairs) - Ages 2, 3, 4, 7, 9, 10and on!
- Language reading, cognitive behavioural
measures
9Participants
- 4 ½ years
- Sub-sample N 1672
- Home visit
- NB over-represented for low language
- 7 years
- Whole sample N 9757
- 10 years
- Whole sample N 5777
- Children with both language and reading data
- 4 ½ 7 199 MZ pairs, 190 DZ same-sex pairs (N
800) - 4 ½ 10 105 MZ pairs, 77 DZ same-sex pairs (N
350)
10Speech Language at 4½
- Speech
- Goldman-Fristoe test of articulation
- Nonword Repetition Task
- Language
- Semantics
- McCarthy Word Knowledge
- McCarthy Verbal Fluency
- Morphosyntax
- BAS Comprehension
- Renfrew Action Pictures Grammar
- And also
- Bus Story
- Phonological Awareness
- McCarthy Verbal Memory
11Reading at 7 10
- Decoding
- 7 years
- Test of Word Reading Efficiency (TOWRE)
- Word and nonword reading subtests
- Administered over the phone
- Comprehension
- 10 years
- PIAT Reading Comprehension
- Sentence-level comprehension
- Administered on the web
12Previous findings Early language
- 9 measures ? 7 General Language 2 Phonology
- General Language
- Moderately heritable (.34)
- Shared environment also important (.50)
- Phonology
- More heritable (.56)
- Shared environment not very important (.15)
- Overlap between language and phonology
- Substantial but not total (rg .64, rc 1.00)
13Previous findings Reading
- Decoding
- TOWRE at 7
- Highly heritable (.70)
- Modest role for shared environment (.15)
- Comprehension
- PIAT Reading Comprehension at 10
- Moderately heritable (.41)
- Shared environment also important (.30)
14Phenotypic associations Predicted
15Phenotypic associations Actual
16Bivariate heritability environmentality
DECODING
17Bivariate heritability environmentality
COMPREHENSION
18Bivariate heritability environmentality
DECODING
COMPREHENSION
19Speech Language ? Decoding
- Early language ? Decoding
- Moderate phenotypic association (.43)
- Half genetic, half environmental
- Early phonology ? Decoding
- Moderate phenotypic association (.35)
- All genetic
20Speech Language ? Reading comprehension
- Early language ?
Reading comprehension - Moderate phenotypic association (.47)
- Half genetic, half environmental
- Early phonology ?
Reading comprehension - Modest phenotypic association (.26)
- All genetic
21Stability across ages domains
- Strength of phenotypic association
- Language at 4 ? reading at 7 (r .43)
- Language at 4 ? reading at 10 (r .47)
- Pattern of genetic and environmental contribution
from early speech language to reading is the
same for decoding at 7 and comprehension at 10
22Speculative Summary
- Genetic core of early phonological skills
- Continues into decoding
- Through decoding also affects reading
comprehension - Genes environments for semantics/syntax
- Both the genes AND environments influence reading
- Both decoding and comprehension
23For the (imminent) future
- Atypical development!
- SLI Dyslexia
24Thankyou!
- Maggie Snowling
- Dorothy Bishop
- Robert Plomin
- Nicole Harlaar
- Yulia Kovas
- Philip Dale
25 26Logic of the Twin Method I
- How similar are the two members of a twin (or any
other sibling) pair? - If very similar, evidence for familiality
- Genes and/or shared environment
- How to untangle genes shared environment?
27Identical twins (monozygotic, MZ)
28Non-identical, fraternal twins (dizygotic, DZ)
29Logic of the Twin Method II
- MZ monozygotic twins
- Share 100 of DNA
- DZ dizygotic twins
- Share 50 of varying DNA (on average)
- MZ and DZ twins share their environment to the
same extent (Equal Environments Assumption)
30Logic of the Twin Method III
- MZs and DZs are both similar to each other ?
shared environment - MZs are more similar to each other than DZs ?
genes
31Sources of variance
- Genes/Heritability
- Effects of alleles at all gene loci that affect
the trait - Shared environment
- any environmental influences that contribute to
the similarity between co-twins - e.g. family environment
- Nonshared environment
- any aspect of environmental influence that makes
co-twins different from each other - e.g. child-specific event, such as illness
32Estimating components of variance
- Heritability
- 2 X difference in MZ and DZ twin correlations.
- Shared environment
- Subtract heritability from MZ correlation
- Nonshared environment
- Subtract MZ correlation from 1
- Includes measurement error
33Twin correlations - example
- MZ twin correlation .80
- DZ twin correlation .50
- h2 (MZ DZ) X 2 .60
- c2 MZ h2 .20
- e2 1 MZ .20
34Model-fitting analysis
- Structural equation modelling
- More comprehensive way of estimating variance
components based on principles of twin method - Allows investigation of sex differences in the
genetic and environmental influences - Allows multivariate analysis
35ACE
36For the (imminent) future
37Speculative Summary
- Genetic core of phonological skills
- Continues into dyslexia
- Also a risk factor for poor comprehension but
only to the extent that poor decoding is a risk
for poor comprehension - Part of SLI heritable phenotype?
- Genes environments for semantics/syntax
- Both the genes AND environments influence reading
- Both decoding and comprehension
- The other half of SLI?