Twin-specific shared environments account for a substantial portion of CTD shared-environment estimates for educational attainment and cannot be interpreted as between-family environmental differences¶
Claim · All claims
Evidence · 1 study · associationalr2·q2
Currency · newest study 2023 · checked against its sources 2026-10-26 (automated, 1 of 1 entry) · not reviewed by a person
Subclaims¶
Reading the evidence codes
q is the design tier, i the impact, n the sample, and the kind with its r
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q2 i? Twin-specific shared environments (T) accounted for 16–25% of variance in PA models, and including them reduced between-family environmental variance to about 10%, well below the CTD C estimate of 43%. → Wolfram 2023
Evidence¶
Wolfram 2023¶
Wolfram, T. & Morris, D. (2023). Conventional twin studies overestimate the environmental differences between families relevant to educational attainment. npj Science of Learning 8, 24. https://doi.org/10.1038/s41539-023-00173-y
q2 · i? · associational · r2
NTFD decomposition of the shared environment in the TwinLife sample, contrasting DZ twin with non-twin sibling correlations (r = 0.6 vs 0.45) to identify twin-specific effects. The best-fitting model attributes only "just 10% of the variance in EA" to between-family environmental differences.
"Taking both assortative mating and twin-specific shared environments into account, our best- fitting model indicated just 10% of the variance in EA could be attributed to between-family environmental differences."
Discussion¶
Related Claims¶
- Adjusting published twin-study ACE estimates for assortative mating raises mean heritability by about 17 points and lowers shared environmental estimates by about 16 points — related
- A Classical Twin Design model of educational attainment in the TwinLife sample estimates shared environmental influence at 43% and additive genetic influence at 34% — related
- Dizygotic twin correlations for educational attainment are consistently higher than non-twin sibling correlations across countries, suggesting twin-specific shared environments are a general phenomenon — related
- The best-fitting NTFD model estimates heritability of educational attainment at 51% and total shared environmental influence at 26%, disaggregated into twin-specific (16%) and sibling-shared (10%) components — related
- Under phenotypic assortment NTFD models, parental education shows no environmental effect on offspring educational attainment once genetic influences are accounted for — related
- Educational achievement is highly heritable, and the common environmental variance is attributable to SES effects — related
- Genetic and environmental variance components of educational achievement decrease with increasing parental SES — related
Page metadata
| Field | Value |
|---|---|
type |
claim |
id |
twin-specific-environments-not-between-family |
title |
Twin-specific shared environments account for a substantial portion of CTD shared-environment estimates for educational attainment and cannot be interpreted as between-family environmental differences |
description |
Twin-specific shared environments account for a substantial portion of CTD shared-environment estimates for educational attainment and cannot be interpreted as between-family environmental differences |
status |
review |
evidence_strength |
moderate |
newest_evidence |
2023 |
source_checked |
2026-10-26 |
generated |
by process:wiki-ingest on 2026-10-26 |
trust |
unverified — no one has confirmed this page's content |
sources |
1 — wolfram-2023 |
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