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

Abstract

Much debate has concerned the separability of executive function abilities and intelligence, with some evidence that the 2 constructs are genetically indistinguishable in children and adolescents but phenotypically and genetically distinct in older adolescents and adults. The current study leveraged data from twin and adoption studies to examine executive function's genetic structure in adulthood (M = 33.15 years, SD = 4.96) and its overlap with intelligence. 1,238 individuals (170 MZ twin pairs, 154 DZ twin pairs, 95 biological sibling pairs, 80 adoptive sibling pairs, and 240 unpaired individuals) completed 6 executive function tasks as well as the Weschler Adult Intelligence Scale-III as part of the Colorado Adoption/Twin study of Life span behavioral development and cognitive aging (CATSLife). Results replicated the unity/diversity model of executive function that distinguishes general executive function abilities (Common EF) from abilities specific to working memory updating (Updating-specific) and mental set shifting (Shifting-specific). In the final model, broad-sense heritability was high for Common EF (h 2 = .72), Updating-specific (h 2 = 1.0), and Shifting-specific (h 2 = .60) factors, as well as for fullscale intelligence (h 2 = .74). Intelligence was phenotypically and genetically correlated with Common EF (r = .49, broad-sense r g = .44) and Updating-specific (r = .60, r g = .69) abilities. This study represents the first executive function study to apply the adoption design. Leveraging the combined twin and adoptive design allowed us to estimate both additive and nonadditive genetic effects underlying these associations. These findings highlight the commonality and separability of executive function and intelligence. Common EF abilities are distinct from intelligence in adulthood, with intelligence also strongly associated with Updating-specific abilities.

The roles of familial transmission and smoking during pregnancy on executive function skills: A sibling-comparison study

“…However, these initial within-family associations between maternal smoking during pregnancy and visual working memory and response inhibition were fully attenuated following covariate adjustment, making causal effects highly unlikely. Further, consistent with the reported high heritability of EF skills (e.g., Anokhin et al, 2010;Coolidge et al, 2000;Friedman et al, 2008;Gustavson et al, 2022;Li & Roberts, 2017), maternal EF significantly predicted offspring EF, above other familial variables that siblings share.…”

“…Twin studies suggest a heritable latent (common) factor that affects all EF subdomains and accounts for 99% of the variance common to all three skills (Friedman et al, 2008). Specific EF skills (i.e., inhibition, set-shifting, and working memory) also generally show moderate heritability, with ranges between 25 and 81% depending on assessment, age, and sex of the sample (e.g., Anokhin et al, 2010;Coolidge et al, 2000;Friedman et al, 2008;Gustavson et al, 2022;Li & Roberts, 2017); noting, however, that reports of heritability of EF skills in toddlers are mixed (e.g., Leve et al, 2013). While there have been several genome-wide association studies (GWAS) of EF, few have identified any genome-wide significant variants.…”

The contribution of latent factors of executive functioning to mind wandering: an experience sampling study

“…Moreover, individual differences in common executive functioning and updating-specific ability are, as expected, strongly related to intelligence (Friedman et al, 2008), and the former is also strongly related to fewer attention-related problems during childhood as evaluated by teachers (Herd et al, 2014). By contrast, shifting-specific ability has shown a moderate negative association with intelligence (Friedman et al, 2008;Herd et al, 2014) and positive associations with attentional-related problems (Friedman et al, 2011;Herd et al, 2014), substance use (Gustavson et al, 2017), and procrastination (Gustavson et al, 2015), although these findings have resulted from mostly exploratory analyses and the negative intelligence correlation was not replicated in a recent study (Gustavson et al, 2022).…”

Associations between executive functions assessed in different contexts in a genetically informative sample.

“…Traditional twin studies cannot estimate more than three variance components in the same model as that model would not be identified, and this limitation can bias variance component estimates (Friedman et al, 2021). For example, in a twin study, if both D and C influence a trait, and only one of the variance components is estimated, the D and C influences can cancel each other out (Gustavson et al, 2022). This canceling out arises because C typically increases DZ twin correlations, while D typically decreases DZ twin correlations relative to MZ twin correlations (Gustavson et al, 2022).…”

“…In adulthood, EFs are phenotypically correlated with, but distinct from, g or IQ, and these correlations vary between EF factors (Blair, 2006; Friedman et al, 2006; Gustavson et al, 2022; Kane & Engle, 2002). Genetically informed studies have identified different patterns of genetic and environmental influence on EFs and g or IQ (Engelhardt et al, 2015; Freis, Morrison, Lessem, et al, 2022; Freis, Morrison, Smolker, et al, 2022; Friedman et al, 2016; Gustavson et al, 2022; Haworth et al, 2010; Tucker-Drob et al, 2013). This consistent pattern of commonality but separability between EFs and g makes g a useful criterion variable in methodological studies of EFs.…”