Genetic and environmental influences on executive functions and intelligence in middle childhood

Abstract

Executive functions (EFs) and intelligence (IQ) are phenotypically correlated. In twin studies, latent variables for EFs and IQ display moderate to high heritability estimates; however, they show variable genetic correlations in twin studies spanning childhood to middle age. We analyzed data from over 11,000 children (9-to 10-year-olds, including 749 twin pairs) in the Adolescent Brain Cognitive Development (ABCD) Study to examine the phenotypic and genetic relations between EFs and IQ in childhood. We identified two EF factors-Common EF and Updating-Specific-which were both related to IQ (rs = 0.64-0.81). Common EF and IQ were heritable (53%-67%), and their genetic correlation (rG = 0.86) was not significantly different than 1. These results suggest that EFs and IQ are phenotypically but not genetically separable in middle childhood, meaning that this phenotypic separability may be influenced by environmental factors.

Genetic and environmental links between executive functioning and effortful control in middle childhood.

“…Univariate twin models revealed that additive genetic and nonshared environmental influences explained differences in measures of EF in middle childhood. Heritability estimates on the Flanker Task, Continuous Performance Task, and Digit Span Backward were generally lower than, but comparable with, previous studies of children and adolescents (e.g., Freis, Morrison, Lessem, et al, 2022; Polderman et al, 2006; Schachar et al, 2011). It is possible that in-home versus lab administration and variations of the task could have contributed to differences in heritability estimates.…”

“…The first goal was to examine the genetic and environmental influences on established measures of EF (Flanker Task, Continuous Performance Task, and Digit Span Backward) and EC (parent-reported Attentional Focusing and Inhibitory Control) in our sample of demographically diverse twin children to compare with previous research. We hypothesized that additive genetic and nonshared environmental influences would explain differences in EF and parent-reported Inhibitory Control (Friedman et al, 2008; Freis, Morrison, Lessem, et al, 2022; Polderman et al, 2006) and that parent-reported Attentional Focusing would be highly heritable with evidence of nonadditive genetic influences (Lemery-Chalfant et al, 2008). The second goal was to assess the genetic and environmental overlap between individual measures of EF and EC, as well as between latent variables of EF and EC.…”

Genetic associations between executive functions and intelligence: A combined twin and adoption study.

“…First, associations between intelligence and Common EF were explained by both genetic influences (total broad-sense genetic correlation; r g = .44) and nonshared environmental influences ( r e = .60). The broad-sense genetic correlation ( r g = .44, 95% CI [.28, .59]) was similar in magnitude to the additive genetic correlations observed in older adolescents (age 17; r a = .57; CIs not reported; Friedman et al, 2008) and middle-aged adults (age 56; r a = .59, 95% CI [.56, 1.00]; Gustavson, Panizzon, Franz, et al, 2018) but was smaller than those observed in younger adolescents (age 10: r a = .86; 95% CI [.45, 1.27]; Freis et al, 2021; age 11: r a = .92; 95% CI [.72, 1.11]; Engelhardt et al, 2016). Even with the extended family design employed here, there was still low power to detect whether the strong genetic correlation was driven by additive genetic influences and dominance genetic influences.…”

“…The above conclusions would account for the fact that phenotypic and genetic associations between Common EF and intelligence approach unity in childhood and early adolescence (Brydges et al, 2012;Engelhardt et al, 2016;Freis et al, 2021) but weaken somewhat in later adolescence and adulthood (Friedman et al, 2008;. The factor structure of EFs appears to be unitary in children before about age 10-12 (Brydges et al, 2014;Hartung et al, 2020;Xu et al, 2013).…”

“…In fact, their Common EF factor had higher factor loadings on their Updating (.92) and Working Memory span (.80) subfactors compared to the Inhibition (.52) and task Switching (.73) factors). Another study of similarly aged children (mean age 10 years), including twins, from the Adolescent Brain and Cognitive Development study also found a high genetic correlation between Common EF and intelligence (r = .64; r a = .86), which did not significantly differ from 1.0 (Freis et al, 2021). However, this study also found that intelligence was correlated with the small amount of variance specific to working memory updating tasks in that sample (r = .81; r a = .36), over and above its relation to Common EF.…”