to what extent is intelligence genetic

Ritchie SJ, Bastin ME, Tucker-Drob EM, Maniega SM, Engelhardt LE, Cox SR, et al. Widespread pleiotropy between two phenotypes can be detected by deriving agenetic correlation (see Glossary) between the two phenotypes. where intelligence partly drives brain differences. Tests that involve the recall of learned information (called crystallised intelligence)such as vocabulary, general knowledge, and some number skillsare relatively stable in mean levels from young adulthood to older age [8, 9]. Curr Opin. Is Intelligence Inherited or Learned? - Sites at Penn State Education and intelligence are traits with evidence of assortative mating; there are reports of cross-spouse correlations of r=0.40 for intelligence and r=0.60 for education [64]. 2007;35:40126. Intelligence is difficult to define IQ tests have been developed by a French person called Binet to measure of intelligence and are used in much psychological research. Third, that they are not associated with confounders with respect to the outcome. Rhein C, Mhle C, Richter-Schmidinger T, Alexopoulos P, Doerfler A, Kornhuber J. Neuroanatomical correlates of intelligence in healthy young adults: the role of basal ganglia volume. Different methods are used to estimate heritability of intelligence (and other phenotypes). A single cognitive performance test was used (UK Biobanks VNR). Although GREML-KIN might recover some of the heritability that is attributable to genetic variants that are in poor LD with common genotyped SNPs, it cannot determine the proportion of the heritability estimate that is due to dynastic effects [36]. cortical parcels) allows researchers to ask whether brain regional differences in brain structure-expression associations are relevant for other correlates of brain structure, using a correlation-of-correlations approach. Hill WD, Davies G, van de Lagemaat LN, Christoforou A, Marioni RE, Fernandes CPD, et al. (See Sniekers, et al (2017) in the 'scientific journal articles for further reading' list in the main summary to read the full research study.). Finally, we want to be clear about prediction of intelligence using genetic or brain imaging variables. We recognise and encourage research on other substantial sources of variation in intelligence, social as well as biological [129]. 2018;360:12227. Nat Rev Neurosci. The word thought is defined as the act of thinking about or considering something: an idea or opinion, or a set of ideas about a particular subject. Scientists have found many indications that IQ is at least partially genetic. For example, epigenetic signatures of smoking, mortality, and inflammation exhibit cognitive associations and regional cortical correlates in older age that overlap with P-FIT areas [124,125,126]. 2015;36:491025. Definitions The Debate Examples Interaction Contemporary Views Nature refers to how genetics influence an individual's personality, whereas nurture refers to how their environment (including relationships and experiences) impacts their development. This appears especially at older ages when a larger proportion of the variance in these measures is probably driven by differences in age-related neurodegenerative processes. This means that there is a third level describing the variance common across all the domains and, thereby, across all the individual cognitive tests. This short test is unlikely to have captured all variance associated with intelligence and, so, this uncaptured cognitive ability variance would also be included in the non-cognitive skills (which would therefore be a misnomer) as evidenced by a genetic correlation of rg=0.31 (SE=0.06) with other measures of intelligence. Genome-wide analysis identifies molecular systems and 149 genetic loci associated with income. 1. [129], some from more genetically inclined (Gottfredson) [2], and two from one of the present authors (Deary) [27, 140]. Biases from assortative mating can be induced by cross-trait assortative mating whereby, for example, more highly educated women might select partners who are taller, resulting in an apparent finding that height is causally associated with education [63]. Reflections on Stephen Jay Goulds the mismeasure of man (1981): a retrospective review. Specifically, loci found to be associated with cognitive abilities might beassociated with the variance from a general factor or they might be associations specific to the domain examined, or even to the specific test within the given domain. We previously summarised genetics and brain imaging associations with intelligence test scores in 2010 [23]. Most believe that a large number of genes each play a small role in. 2018;9:1905. A genetic correlation co-efficient is derived using all SNPs from a GWAS regardless of the SNPs levels of association with a trait. 2019;24:18297. PubMed Behav Brain Sci. Distributed neural system for general intelligence revealed by lesion mapping. We address research that combines genetics and brain imaging in studying intelligence differences. Intelligence: knowns and unknowns. The researcher Linda Gottfredson's definition of intelligence is often repeated: "Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. Specifically, the relative importance of vertical pleiotropy and horizontal pleiotropy in the generation of genetic correlations between cognitive ability and brain variables is currently unknown. Zenderland L. Measuring minds: Henry Herbert Goddard and the origins of American intelligence testing. However, we consider that to be a lesson for us, and for the field, about the sorts of studies that could be done. Wheater ENW, Stoye DQ, Cox SR, Wardlaw JM, Drake AJ, Bastin ME, et al. This is mostly based on the testing of genetic variants calledsingle nucleotide polymorphisms (SNPs) (see Glossary). This is because the resulting heritability estimate is, potentially, a combination of direct genetic effects (genetic variation in an organism that is associated with phenotypic variation in the same organism) and indirect genetic effects (where genetic endowment of one organism is associated with the phenotype of another organism). Genetics & Intelligence | Is IQ Genetic? - Study.com Looking down on human intelligence: from psychometrics to the brain. Having larger volumes of brain (and tissues therein) appears to be relatively strongly related to having greater numbers of neurons [107]. New York, NY, USA: Free Press; 1994. But now a new study of nearly 80,000 people, published in Nature . Twin and family studies report that genetic differences are associated with individual differences in intelligence test scores (Box2). Heritability in the genomics eraconcepts and misconceptions. GWAS can include millions of mostly common single nucleotide polymorphisms from across the genome. Cereb Cortex. Intelligence. Cognitive aging and dementia: a life-span perspective. Mol Psychiatry. Genetics and general cognitive ability | Nature Intelligence, more appropriately called general cognitive ability, reflects someone's performance across a broad range of varying tests. Heritabilitydescribes the proportion (often expressed as a percentage) of phenotypic variation in a tested sample of people that can be accounted for by genetic variation [142]. Calming, consensual oil was poured on intelligences stormy waters in 1996, by the American Psychological Association (APA). 2017 Jul;49(7):1107-1112. doi: 10.1038/ng.3869. Cell Rep. 2017;21:67991. 2008;3:51831. The intelligence-cortical thickness relationship changes over the life course, with negative associations reported in 10-year-olds [82,83,84]. 2020;3:456. Is Intelligence Genetic? - Examined Existence Thus, a blood sample at birth in these samplespredicts intelligence with about the same effect size as parental socioeconomic status, i.e. 2011;16:9961005. Psychol Sci. They do not indicate which genetic variants are associated with trait variation. F Associations between lesion locus and intelligence in cortical (top) and subcortical (bottom) loci (age M=49, SD=16years; N=241); reproduced with permission from [80]. 2019;10:5741. Often, in human studies, only additive genetic factors are considered. Plomin R, Deary IJ. Mol Psychiatry. Curr Biol. Nat Genet. People with higher intelligence in early life are, up to several decades later, less likely to suffer from poor health and then die from all causes, and, specifically, from heart disease, stroke, respiratory disease, smoking-related cancers, digestive diseases, dementia, accidents, and suicide, among other causes. C Associations between cortical thickness and intelligence in children (age range 618 years; N=216); reproduced with permission from [83]. Hill WD, Arslan RC, Xia C, Luciano M, Amador C, Navarro P, et al. GWAS data sets results on intelligence have found associations between SNP variation and tissue-specific gene expression across many of the brains cortical regions (Fig. Intelligence. Scores on all tests of cognitive ability correlate positively. This raises ethical issuesoutlined more elsewhere [52]which should be addressed by well-informed professionals and lay people from appropriate interest groups and areas of expertise. Normative brain size variation and brain shape diversity in humans. The phenotypic nature of intelligence, too, has areas of contention: some areas of the neuroscience and cognitive literature focus on experimental cognitive tasks that assess aspects of so-called executive functioning, in contrast to the psychometric tests upon which intelligence scores are based. Corley J, Cox SR, Harris SE, Hernandez MCV, Maniega SM, Bastin ME, et al. bioRxiv. Intelligence is challenging to study, in part because it can be defined and measured in different ways. Cox SR, Ritchie SJ, Tucker-Drob EM, Liewald DC, Hagenaars SP, Davies G, et al. In a GWAS, a SNP is treated as the statistical unit of association. Mol Psychiatry. Kovacs K, Conway ARA. Data from lesion studies and the ageing process can be seen as helpful in triangulating whether certain brain regions might be necessary for higher intelligence, rather than being related due to confounding factors (such as pre-existing, lifetime differences in brain volumes, in the example of ageing). We should have liked there to have been more amalgamated brain-cognition-genetics studies, and we should have liked more integrated sections, examples and ideas to review. 2019. https://doi.org/10.1038/s41380-019-0616-9. Gignac GE, Bates TC. 2018;28:295975. IJD and SRC were supported by the UKRI Medical Research Council (MR/R024065/1) and the United States Department of Human Sciences National Institutes of Health (1R01AG054628-01A1). Nisbett RE, Aronson J, Blair C, Dickens W, Flynn J, Halpern, et al. A re-analysis of those data including only healthy adults estimated the association at r=0.31; this rose to r=0.39 when it included only the studies judged to have used better-quality intelligence testing [72]. medRxiv. Intelligence: A very short introduction (2nd edition). Google Scholar. Nat Genet. Using genomic structural equation modelling [29] it was found that a genetic general factor explained, on average, 58.4% (SE=4.8%, ranging from 9 to 95% for individual tests) of the genetic variance across seven cognitive testsin people with European ancestry. Pleiotropy (see Glossary) describes instances where variation at a region of the genome is associated with multiple phenotypes. Spearman C. General Intelligence, objectively determined and measured. Penke L, Maniega SM, Bastin ME, Hernndez MCV, Murray C, Royle NA, et al. Brain Struct Funct. Illustrated here is the finding that tissue-specific expression in and across the brain is associated with intelligence; the full list of associations is in the original report [46]. 2015;36:140716. Heritability estimates of intelligence that use GREML-SC have typically been between 20 and 30% [30, 31, 143]. Is Intelligence Genetic? - Genes' Influence on Intellectual Abilities Molecular genetic contributions to social deprivation and household income in UK Biobank. Genetic correlations derived using GWAS data sets have demonstrated that genetic variants associated with higher intelligence test scores are, on average, also associated with, for example, longevity [46], better physical health [58], and more advantaged socioeconomic position [16, 50, 59]. MR results have indicated that intelligence and education probably have a bi-directional causal relationship [61], and that intelligence might have some causal association with, for example, Alzheimers disease that is independent of any protective effects of education [61]. 2019;2:16981. PubMed Central Investigating the genetic architecture of non-cognitive skills using GWAS-by-subtraction. We summarise new brain imaging-intelligence findings, including whole-brain associations and grey and white matter associations. 2014;9:e93623. The focus is on genetic variation and brain imaging-derived differences, including where those two sources overlap. J Neurosci. Genetics and Learning: How the Genes Influence Educational Attainment These divisions are also in part because research on the statistical phenotypic nature of intelligence has been going on for more than a century. New methods have blossomed in these fields, and debates and enquiry into the merits of these will continue apace. 2014;44:2632. A study which found that a polygenic score for intelligence predicted 35% of intelligence differences in a new sample also reported that this association was partially mediated to a small extent by brain cortical thickness and surface area of the anterior cingulate cortex, the prefrontal cortex, the insula, and the medial temporal cortex [120]. Yet, much work is required before we understand whether and how such specific microscopic features (some of which are estimated with neuroimaging) might specifically give rise to intelligence differences. NeuroImage. Biological annotation of genetic loci associated with intelligence in a meta-analysis of 87,740 individuals. 2020. https://doi.org/10.1038/s41562-020-00936-2. Intelligence is what the tests test. That much-quoted last short sentence was not Borings opinion; rather, it was his saying that that is what one would think if one did not know the research findings. 2014;4:e341. closer than a second cousin). Importantly, whereas it uses the same genetic data as GREML-SC, GREML-KIN uses samples with a dense and known pedigree to derive additional matrices to capture additional sources of variance from genetic variants that are in poor LD with common genotyped SNPs and to control for the effect of environmental influences. Longevity, intracranial volume, self-rated health, and head circumference all show positive genetic correlations with intelligence. Blog / May 20, 2021 00:00 00:00 In 1946, J.B.S. The three studies above used polygenic scores to provide out-of-sample predictions of intelligence based solely on DNA-SNP data [31, 46, 47]. Intelligence. 2007;35:1321. PubMedGoogle Scholar. Davies G, Harris SE, Reynolds CA, Payton A, Knight HM, Liewald DC, et al. Google Scholar. P-FIT theory receives support from some newer empirical findings (Fig. Annu Rev Psychol. It is likely that a large number of genes are involved, each of which makes only a small contribution to a persons intelligence. 1996;51:77101. Integration of structural and functional data (along with other modalities) will be central to testing broader theories about the nature of intelligence. Jensen AR. Massive IQ gains in 14 nations: What IQ tests really measure. Brain volume and intelligence: the moderating role of intelligence measurement quality. 2019;1:17796. Bioinformatic analyses of these data have identified associations with genes expressed in the brain and other cortical tissues as well as genes whose level of expression is elevated both pre- and postnatally. Am J Psychol. Mol Psychiatry. 2020. https://doi.org/10.1177/0956797620904450. Cambridge, UK: Cambridge University Press; 2016. Such approaches have the potential to more directly test the specificity of brain-based network theories of intelligence, such as the P-FIT. The second of the three studies to appear found 148 loci (53 novel when it appeared online) associated with intelligence, with a sample size of 300,046 participants [31]. Intelligence - ScienceDirect Internet Explorer). 2012;17:102630. For example, if white matter health is important for higher intelligence, we would expect declines in both to be correlated [94]. 2010;31:160925. Polygenic scores can also make predictions across traits by deriving a polygenic score for intelligence and using it to predict health, or brain imaging traits, for example. 2018;373:20170284. This finding has been replicated consistently since Charles Spearman discovered it in 1904 [4]. To obtain But. In 2018, three studies, using substantially overlapping samples, attained sample sizes of over 200,000 participants and found hundreds of genetic loci significantly associated with intelligence [31, 46, 47]. Larger effect sizes for brain-intelligence associations can be found with multiple measures of white matter microstructure. Nat Genet. Meta-analysis of the heritability of human traits based on fifty years of twin studies. Nature vs. Nurture: Genetic and Environmental Influences - Verywell Mind J Exp Psychol Gen. 2016;145:114159. Alzheimers Res Ther. A hierarchy without a general factor. Marioni RE, McCrae AF, Bressler J, Colicino E, Hannon E, Li S, et al. The resulting GWAS of so-called non-cognitive skills found a heritability of 6.6% (SE=0.2%), and a positive genetic correlation with schizophrenia of rg=0.26 (SE=0.02). On the other hand, genetic variants associated with higher intelligence test scores are, typically, slightly positively associated with autism spectrum disorder and anorexia nervosa [46]. It identified that variations in the structure and function of lateral and medial frontal, parietal, lateral temporal, and lateral occipital cortex, and underlying white matter connectivity (such as the arcuate fasciculus) were associated with individual differences in intelligence. The Cold Spring Harbor Laboratory offers an interactive tool called Genes to Cognition that provides information about many aspects of the genetics of neuroscience. Spearman [4] discovered the positive matrix of correlations among cognitive performance assessments, and developed a two-factor theory of intelligence, which had general intelligence, which he called g, and specific abilities, which he called s. This describes the finding that multiple phenotypes can be associated with genetic variation at the same locus. Or do you think that the IQ is a matter of education and nurture? 2019;30:270819. Genome-wide association meta-analysis of 78,308 individuals identifies new loci and genes influencing human intelligence. Dubois J, Galdi P, Paul LK, Adolphs R. A distributed brain network predicts general intelligence from resting-state human neuroimaging data. However, these shared genetic associationsdetected by genetic correlations or polygenic scorescan arise due to vertical pleiotropy, horizontal pleiotropy, or spurious pleiotropy, which we explain below [57]. [146]). However, even finding correlated changes between intelligence test scores and changes in a given brain region or pathway is still potentially confounded. A major contribution to this study was from the large UK Biobank samples short Verbal and Numerical Reasoning test (VNR; called the fluid test by UK Biobank, which is a misnomer). Here we have shown that multiple tests (up to a number k) are used to assess each domain of cognitive capability. Article GREML-SC, sometimes referred to as the GCTA method, was the first DNA-based genetic method used to derive an estimate of heritability for intelligence [30]. This tests how closely peoples similarity in cognitive test scores associates with their genetic similarity, the latter being based on hundreds of thousands of SNPs. Changes in thickness and surface area of the human cortex and their relationship with intelligence. Deary IJ. GWASs of educational attainment show high genetic correlations with intelligence (rg=0.700.80 [46]) and have identified 1271 independent genome-wide significant SNPs [50]. Mol Psychiatry. g might be important, but it is far from being all that matters. Is Intelligence Genetic? - Inverse Intellectual Ability and Heritability Many researchers have studied how our intellectual abilities are affected by genetics. Other studies have examined variations across the entire genomes of many people (an approach called genome-wide association studies or GWAS) to determine whether any specific areas of the genome are associated with IQ. Gottfredson LS. Eur Heart J. The caudate, which had also previously been implicated in intelligence differences, albeit in smaller samples [86, 87], was also correlated with intelligence in the UK Biobank analysis (r0.13), but only hippocampal (r=0.05) and thalamic volumes (r=0.19) showed unique associations with intelligence in a multivariate model including all subcortical structures. Deary, I.J., Cox, S.R. It is a correlation between the tested genetically heritable elements of each trait. Our emphasis herein is on results from the newer, DNA-based studies rather than on traditional twin and family studies. PubMed: 29335645. There are fields that might help to bridge the gap, and contribute toward understanding intelligence differences, such as epigenetics [121, 122], transcriptomics, proteomics, virtual histology, and others. Mol. A negative genetic correlation describes instances where the genetic variants associated with higher intelligence are also those that are associated with a lower value of the trait or a lower likelihood of developing the disorder. These authors contributed equally: Ian J. Deary, Simon R. Cox, W. David Hill, Lothian Birth Cohorts group, Department of Psychology, University of Edinburgh, 7 George Square, Edinburgh, EH8 9JZ, UK, Ian J. Deary,Simon R. Cox&W. David Hill, You can also search for this author in Perspect Psychol Sci. 2018;50:22937. 2016;59:6471. PubMed 2017;22:33645. Flynn [137] found that intelligence test scores increased across the years and generations of the middle two quarters of the 20th century. Genetics and intelligence differences: five special findings Psychometric Monographs No. 2020;225:2387402. The pleiotropy identified between intelligence and cortical measures also requires further examination. The heritability of intelligence increases throughout development Unlike the other findings, this one is limited to a specific domain, general cognitive ability (intelligence), but it is one of the most surprising and counterintuitive findings from behavioral genetics. Whereas this assumption has been found not to hold in some situations, the inflation of the resulting heritability estimate is thought to be negligible [144]. Gardner H Frames of mind: The theory of multiple intelligences. Together, they accounted for about 10% of intelligence differences in 73-year-olds. Relatedness disequilibrium regression estimates heritability without environmental bias. The proportion of variance explained by polygenic scores rises with sample size, so the predictive power is likely to rise as sample sizes increase [51]. Mol Psychiatry. Plomin R, von Stumm S. The new genetics of intelligence. SNP variation associated with intelligence has been linked to tissue-specific gene expression in specific classes of neuron, including pyramidal neurons of the somatosensory cortex, the CA1 region of the hippocampus, midbrain embryonic GABAergic neurons, [53] and medium spiny neurons [47]. Neurobiology of intelligence: science and ethics - Nature

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