Despite the importance of learning abilities and disabilities in education and child development, little is known about their genetic and environmental origins in the early school years.
Despite the importance of learning abilities and disabilities
in education and child development, little is known
about their genetic and environmental origins in the
early school years. We report results for English (which
includes reading, writing, and speaking), mathematics,
and science as well as general cognitive ability in a large
and representative sample of U.K. twins studied at 7, 9,
and 10 years of age. Although preliminary reports of
some of these data have been published, the purpose of
this monograph is to present new univariate, multivariate,
and longitudinal analyses that systematically examine
genetic and environmental influences for the entire sample
at all ages for all measures for both the low extremes
(disabilities) and the entire sample (abilities).
English, mathematics, and science yielded similarly
high heritabilities and modest shared environmental
influences at 7, 9, and 10 years despite major changes
in content across these years. We draw three conclusions
that go beyond estimating heritability. First, the abnormal
is normal: low performance is the quantitative extreme
of the same genetic and environmental influences
operate throughout the normal distribution. Second, continuity
is genetic and change is environmental: longitudinal
analyses suggest that age-to-age stability is primarily
mediated genetically whereas the environment contributes
to change from age to age. Third, genes are generalists
and environments are specialists: multivariate analyses
indicate that genes largely contribute to similarity
in performance within and between the three domains--
and with general cognitive ability--whereas the environment
contributes to differences in performance.
These conclusions have far-reaching implications for
education and child development as well as for molecular
genetics and neuroscience.
