Abstract
Cognitive abilities vary among people. About 40–50% of this variability is due to general intelligence (g), which reflects the positive correlation among individuals' scores on diverse cognitive ability tests. g is positively correlated with many life outcomes, such as education, occupational status and health, motivating the investigation of its underlying biology. In psychometric research, a distinction is made between general fluid intelligence (gF) – the ability to reason in novel situations – and general crystallized intelligence (gC) – the ability to apply acquired knowledge. This distinction is supported by developmental and cognitive neuroscience studies. Classical epidemiological studies and recent genome-wide association studies (GWASs) have established that these cognitive traits have a large genetic component. However, no robust genetic associations have been published thus far due largely to the known polygenic nature of these traits and insufficient sample sizes. Here, using two GWAS datasets, in which the polygenicity of gF and gC traits was previously confirmed, a gene- and pathway-based approach was undertaken with the aim of characterizing and differentiating their genetic architecture. Pathway analysis, using genes selected on the basis of relaxed criteria, revealed notable differences between these two traits. gF appeared to be characterized by genes affecting the quantity and quality of neurons and therefore neuronal efficiency, whereas long-term depression (LTD) seemed to underlie gC. Thus, this study supports the gF–gC distinction at the genetic level and identifies functional annotations and pathways worthy of further investigation.
Highlights
A large proportion (40-50%) of inter-individual variability in cognitive abilities is due to general intelligence (g), a quantitative trait that reflects the positive correlation among an individual’s scores on diverse cognitive ability tests (Deary, 2012; Spearman, 1904)
A distinction is made between general fluid intelligence - the ability to reason in novel situations - and general crystallized intelligence - the ability to apply acquired knowledge
As these genome-wide association studies (GWASs) data results were not presented in the previous study (Davies et al, 2011), the traditional SNPlevel diagnostics and results are provided in the Supporting Information (Figure S1 and Dataset S1)
Summary
A large proportion (40-50%) of inter-individual variability in cognitive abilities is due to general intelligence (g), a quantitative trait that reflects the positive correlation among an individual’s scores on diverse cognitive ability tests (Deary, 2012; Spearman, 1904). A high g score is associated with many favorable life outcomes (Deary & Batty, 2011). GF and gC are correlated at least 50% based on twin studies (Wainwright et al, 2005) and more so early and late in life (Li et al, 2004), developmental and cognitive neuroscience studies largely support the distinction between them. GF declines earlier and more rapidly than gC (Craik & Bialystok, 2006; Salthouse, 2004); in development, measures of verbal (gC) and non-verbal (gF) intelligence correlate differently with changes in brain structure (Ramsden et al, 2011). At the population level, large gains in performance have been observed for tests that are strongly associated with gF, but not with gC (Flynn, 2007)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
