Etiological distinction of working memory components in relation to mathematics.

Working memory has been consistently associated with mathematics achievement, although the etiology of these relations remains poorly understood. The present study examined the genetic and environmental underpinnings of math story problem solving, timed calculation, and untimed calculation alongside working memory components in 12-year-old monozygotic (n = 105) and same-sex dizygotic (n = 143) twin pairs. Results indicated significant phenotypic correlation between each working memory component and all mathematics outcomes (r = 0.18 - 0.33). Additive genetic influences shared between the visuo-spatial sketchpad and mathematics achievement was significant, accounting for roughly 89% of the observed correlation. In addition, genetic covariance was found between the phonological loop and math story problem solving. In contrast, despite there being a significant observed relationship between phonological loop and timed and untimed calculation, there was no significant genetic or environmental covariance between the phonological loop and timed or untimed calculation skills. Further analyses indicated that genetic overlap between the visuo-spatial sketchpad and math story problem solving and math fluency was distinct from general genetic factors, whereas g, phonological loop, and mathematics shared generalist genes. Thus, although each working memory component was related to mathematics, the etiology of their relationships may be distinct

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student assessing by finding difficulty factor

Longitudinal stability in reading comprehension is largely heritable from grades 1 to 6.

Reading comprehension is a foundational academic skill and significant attention has focused on reading development. This report is the first to examine the stability and change in genetic and environmental influences on reading comprehension across Grades 1 to 6. This developmental range is particularly important because it encompasses the timespan in which most children move from learning how to read to using reading for learning. Longitudinal simplex models were fitted separately for two independent twin samples (N = 706; N = 976). Results suggested that the shared environment contributed to variance in early but not later reading. Instead, stability in reading development was largely mediated by continuous genetic influences. Thus, although reading is clearly a learned skill and the environment remains important for reading development, individual differences in reading comprehension appear to be also influenced by a core of genetic stability that persists through the developmental course of reading

Proportions of variance in Reading Comprehension due to age-specific novel and continuous transmitted sources.

<p>Variance is decomposed into genetic (A), shared environmental (C), and nonshared environmental (E) effects. Age-specific novel effects are represented by the solid portions of the bars and continuous transmitted effects are represented by the line-shaded portions of the bars.</p

Phenotypic Correlations for all Grades of Reading Comprehension.

<p><i>Note. N</i>s in parentheses are for individuals. All correlations are significant at <i>p</i> <.001</p><p>Phenotypic Correlations for all Grades of Reading Comprehension.</p