to what extent is intelligence genetic

If intelligence is supported by a large distributed network of brain regions and their connections, there may well be many potential cerebral routes to intelligence differences, and to intellectual changes. Human cognitive ability is influenced by genetic variation in components of postsynaptic signalling complexes assembled by NMDA receptors and MAGUK proteins. 2016;7:13629. Mendelian randomisation (MR; see Glossary) studies move beyond associations between intelligence and health variables to seeking evidence that one phenotype might be causally related to another. A positive genetic correlation indicates that the genetic variants associated with higher intelligence test scores are associated with a greater value of the trait or a higher likelihood of developing the disorder. Tucker-Drob EM. Whereas we acknowledge inconsistencies in white matter tract nomenclature and identification, there is emerging evidence that long range cortico-cortical (association pathways), the genu (more so than splenium) of the corpus callosum, and subcortico-cortical (mainly thalamic) pathways show numerically larger associations with intelligence than projection fibres (though all r<0.11; [73]). Intelligence therefore depends, to some extent, on structural differences in the brain that are under genetic control, indicating a partly neuroanatomical (structural) explanation for the high . J Exp Psychol Gen. 2016;145:114159. 2014;19:5559. 2012;17:31524. The focus is on genetic variation and brain imaging-derived differences, including where those two sources overlap. Trampush JW, Yang MLZ, Yu J, Knowles E, Davies G, Liewald DC, et al. 2020;31:792806. Mol Psychiatry. General intelligence (g), as a statistical phenomenon, is a universal finding from different batteries of cognitive tests. Deary IJ, Penke L, Johnson W. The neuroscience of human intelligence differences. The field changed to the conducting of GWAS (see Glossary) that are agnostic regarding which, if any, loci are associated with the trait of interest. We address research that combines genetics and brain imaging in studying intelligence differences. To What Extent Is Intelligence Inherited? GREML-SC assumes that SNP effects are normally distributed as well as independent ofLD (see Glossary), and inversely proportionate to minor allele frequency [33]. An association was identified between cg12507869 on chromosome 10 in the INPP5A gene and cognitive ability, as measured using the Mini-Mental State Examination, and with phonemic verbal fluency [121]. Article 2019;145:273301. Intelligence: A very short introduction (2nd edition). In the context of GWAS it is typically only the additive genetic factors that are considered from variants that are in linkage disequilibrium (see below) with the common SNPs used, and so the heritability estimate is the narrow-sense heritability. This is an attempt to ensure that the similarity in environment between family members is not captured by genetic the genomic relationship matrix, which can result in an inflation of the heritability estimate. In this section we summarise some recent studies that have integrated genes and brains to try tounderstand intelligence differences, before discussing their implications and potential future directions for a more integrative and nuanced account of some biological underpinnings of intelligence differences. 2005;33:45572. Furthermore, quantitative genetics theory predicts that epistasis is unlikely to be associated with a substantial amount of phenotypic variance [35]. Schiepers OJG, Harris SE, Gow AJ, Pattie A, Brett CE, Starr JM, et al. Gained x Inherited intelligence Is your IQ influenced more by genes or Science. Psychol Bull. The three studies above used polygenic scores to provide out-of-sample predictions of intelligence based solely on DNA-SNP data [31, 46, 47]. Elements of intelligence include the ability to reason, plan, solve problems, think abstractly, and understand complex ideas. URL of this page: https://medlineplus.gov/genetics/understanding/traits/intelligence/. Studies of the DNA of hundreds of thousands of unrelated people suggest that only around 30% of the variation in intelligence is inherited. where intelligence partly drives brain differences. Massive IQ gains in 14 nations: What IQ tests really measure. Neisser U, Boodoo G, Bouchard TJ, Boykin AW, Brody N, Ceci SJ, et al. Arc requires PSD95 for assembly into postsynaptic complexes involved with neural dysfunction and intelligence. Brain Res. 1916;8:27181. Hence, overall brain volume links to intelligence and to a large extent shares a common genetic origin. Are processing speed tasks biomarkers of cognitive aging? 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. 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. 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. 2014;20:98108. This question has been one of the most controversial topics throughout the history of psychology and remains a hot topic of debate to this day. Am Psychol. Nisbett RE, Aronson J, Blair C, Dickens W, Flynn J, Halpern, et al. Intelligence is a core construct in differential psychology and behavioural genetics, and should be so in cognitive neuroscience. Polderman TJC, Benyamin B, de Leeuw CA, Sullivan PF, van Bochoven A, Visscher PM, et al. Behav Sci. 2020;3:456. 2015;47:7029. These included studies by many of the most prominent researchers over that time, including those who had claimed not have found a general intelligence factor. Zimmermann J, Griffiths JD, McIntosh AR. 2014;9:e93623. For example, verbal fluency IQ tests could be used to give an estimate of intelligence, if a study wanted to look at how genes affect the brain's ability to receive and process information. Larger effect sizes for brain-intelligence associations can be found with multiple measures of white matter microstructure. 28 Citations 448 Altmetric Metrics Abstract Individual differences in human intelligence, as assessed using cognitive test scores, have a well-replicated, hierarchical phenotypic covariance. Genetics and intelligence differences: five special findings - Nature Cereb Cortex. Aggleton JP, OMara SM, Vann SD, Wright NF, Tsanov M, Erichsen JT. Is the probability of having twins determined by genetics? GWAS can include millions of mostly common single nucleotide polymorphisms from across the genome. Wheater ENW, Stoye DQ, Cox SR, Wardlaw JM, Drake AJ, Bastin ME, et al. Strong genetic of overlap between executive functions and intelligence. Intelligence - Family, Twin, And Adoption Studies - JRank Karama S, Bastin ME, Murray C, Royle NA, Penke L, Maniega SM, et al. In a study investigating this phenomenon, SNPs associated with lower intelligence test scores, less education, and an increased risk for schizophrenia were also associated with early developmental processes [68]. This is a potential issue for examining more mechanistic accounts of intelligence differences, as variance that is both common across cognitive tests, and the variance that is specific to any particular testing domain or single test might be included together. SNP is pronounced snip. Jung RE, Chohan MO. Nat Commun. Lest the reader makes the error of over-extending intelligences demesne and importance, the APA Task Force ended by emphasisingas do wethat there are many cognitive and non-cognitive aspects of human differences that are not captured by intelligence tests and general intelligence. Tamnes CK, stby Y, Walhovd KB, Westlye LT, Due-Tnnessen, Fjell AM. Cambridge, UK: Cambridge University Press; 1998. These divisions are also in part because research on the statistical phenotypic nature of intelligence has been going on for more than a century. Galton F. Hereditary genius: An inquiry into its laws and consequences. The finding that intelligence is heritable has been replicated across multiple data sets sourced from different countries and times [28]. There are robust associations between intelligence test scores and apparently simpler processing speed measures such as reaction times [21] and the psychophysical procedure called inspection time [22]. 2019;51:163744. For example, those brain cortical regions that showed a stronger relationship between greater triacylglycerol expression and greater cortical thickness were also the regions where thickness was more strongly associated with general cognitive ability [128]. E Associations between intelligence test scores and regional cortical volume (left), and white matter tract fractional anisotropy (upper right, blue) and mean diffusivity (lower right, orange) in middle-aged and older adults (age range 4481 years; Nrange=720118,426); reproduced with permission from [73]. A related difficulty in the interpretation of genetic correlations between intelligence and brain morphology arises from non-transmitted genetic effects [36, 37]. Pakkenberg B, Gundersen HJG. Among many topics addressed, they recognised the prominence of the psychometric testing approach to intelligence differences, and the hierarchy with the g factor at the apex; they summarised the stability of intelligence test scores, their predictive validity for education, work and other life outcomes, their having environmental and genetic origins, the Flynn effect, and various types of group differences. Multi-trait analysis of genome-wide association summary statistics using MTAG. There could be more (up to a number N), depending on the types of specific tests included in the battery. B A meta-analysis of functional and structural (voxel-based morphometry only) studies of intelligence; reproduced with permission from [85]. There is a well-replicated, modest positive association between brain size and intelligence test scores. Intelligence: knowns and unknowns. For example, if white matter health is important for higher intelligence, we would expect declines in both to be correlated [94]. IJD and WDH were supported by Age UK (Disconnected Mind grant). They analysed data from the USAs National Longitudinal Survey of Youth 1979 and found that higher intelligence in late adolescence/early adulthood was related to better life outcomes by the 30s. The book was strongly and widely criticised, especially for its dealing with ethnic group differences, and for not havingpublished its analyses via peer review. 2017 Sep 27;49(10 ):1558. However, there is still mystery about what causes the covariation. The Paradox of Intelligence: Heritability and Malleability Coexist in This can be seen most clearly when examining genetic loci previously associated with the Trails B cognitive test; it was shown [29] that Trails Bs scores associations with genetic loci were shared with other tests of cognitive ability, and so were more general than initially assumed. For example, if a person's level of intelligence is similar to that of their parents, is that similarity due to genetic factors passed down from parent to child, to shared environmental factors, or (most likely) to a combination of both? PubMed Central Brumpton B, Sanderson E, Heibron K, Hartwig FP, Harrison S, Vie GA, et al. Davies G, Tenesa A, Payton A, Yang J, Harris SE, Liewald D, et al. Positive association between cognitive ability and cortical thickness in a representative US sample of healthy 6 to 18 year-olds. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Hillary RF, Stevenson AJ, Cox SR, McCartney DL, Harris SE, Seeboth A, et al. However, it is not a genetic relation, but rather, an educational one. 1904;15:20192. Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. By understanding the forms of pleiotropy responsible for such genetic correlations, more mechanistic accounts of intelligence differences can be formulated. The names applied to domains are common-sense labels based on the apparently shared contents of the specific tests that contribute to them. Mol Psychiatry. For example, John Carroll re-analysed correlation matrices of diverse cognitive tests from 400+ studies conducted in the 20th century [5]. PubMedGoogle Scholar. Study of 300,486 individuals identifies 148 independent genetic loci influencing general cognitive function. 2010;25:21928. 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. Spatial gradient of microstructural changes in normal-appearing white matter in tracts affected by white matter hyperintensities in older age. [102]). Associations between vascular risk factors and brain MRI indices in UK Biobank. Childhood cognitive ability accounts for associations between cognitive ability and brain cortical thickness in old age. Intelligence. Curr Opin Psychol. 2019;2:16981. Mainstream science on intelligence: an editorial with 52 signatories, history, and bibliography. 2019;1:17796. On the other hand, prediction of the intelligence of an individual from genetic or neuroimaging variables is not a practical or, in our view, desirable aim. 2018;50:111221. Intelligence. 2010;64:113. effects of aging, amyloid and Alzheimers disease on the cerebral cortex and the hippocampus. Tests that involve active mental work (aspects of fluid intelligence) decline in mean levels from young or middle adulthood to older age [8, 9]. Front Neurol. 2018;50:130410. Chicago, IL, USA: The University of Chicago Press; 1938. Subcortical intelligence: Caudate volume predicts IQ in healthy adults. GREML-KIN has the same assumptions as GREML-SC. 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). Are there true sex differences? 2010;31:2292307. Contributions of longitudinal and lesion studies. Thickness of the cerebral cortex shows positive association with blood levels of tricylglycerols carrying 18-carbon fatty acids. Blog / May 20, 2021 00:00 00:00 In 1946, J.B.S. Moreover, environmental influence on the heritability of education was suggested by finding that a polygenic score (see below) predicting education in non-adoptees accounted for twice the phenotypic variance of a polygenic risk score applied to adoptees [38]. 2020. https://doi.org/10.1038/s41562-020-00936-2. You are using a browser version with limited support for CSS. As with twin and family-based methods, genetic similarity is compared with phenotypic similarity. For the next 6 years, GWASs conducted on intelligence test scores were largely unsuccessful in identifying associated genetic loci [42,43,44,45]. The effect of network thresholding and weighting on structural brain networks in the UK Biobank. Meta-analysis of the heritability of human traits based on fifty years of twin studies. closer than a second cousin). We summarise new brain imaging-intelligence findings, including whole-brain associations and grey and white matter associations. protein expression) and how these go on to facilitate the neurobiological machinery whose properties can be estimated and tested for any associations with differences in general cognitive ability. Trends Neurosci Educ. 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]. It was questioned whether intelligence was attributed to genetic or environmental factors. 2012;67:13059. Calvin CM, Batty GD, Der G, Brett CE, Taylor A, Pattie A, et al. The first human behavioral genetic research on intelligence and mental illness began in the 1920s, when environmentalism (the theory that behaviour is a result of nongenetic factors such as various childhood experiences) became popular and before Nazi Germany's abuse of genetics made the notion of hereditary influence abhorrent.Although genetic research on human behaviour continued . Longevity, intracranial volume, self-rated health, and head circumference all show positive genetic correlations with intelligence. Malanchini M, Rimfeld K, Allegrini AG, Ritchie SJ, Plomin R. Cognitive ability and education: how behavioural genetic research has advanced our knowledge and understanding of their association. Consequently, reviews that focus solely on, say, executive function(s) or working memory might not fully bring out their strong phenotypic [8, 113,114,115], genotypic [116, 117] and neurostructural (Box3) overlaps with psychometric intelligence. Measures such as fractional anisotropy (FA; an index of the directional coherence of diffusion) and mean diffusivity (MD; the average magnitude of diffusion) are commonly used metrics. If a large sample of people take two different, diverse sets of cognitive tests, the two g factors from them correlate highly [6]; thus, g is not idiosyncratic, and its ranking of individuals does not differ substantially depending on the test battery. More succinctly, intelligence has been described as, rapid and accurate problem solving [3]. Google Scholar. 2018;28:295975. Dubois J, Galdi P, Paul LK, Adolphs R. A distributed brain network predicts general intelligence from resting-state human neuroimaging data. However, there is a lack when it comes to understanding why some people are more intelligent than others. 2018;165:13847. Mol Psychiatry. Vandenberg SG. 2020;225:2387402. Intelligence - ScienceDirect As a result of the controversy caused by The Bell Curve, the APA put together a Task Force, chaired by cognitive psychology doyen Neisser [139], to tell non-experts what was (solidly) known and (as-yet) unknown about intelligence test score differences. Genet Epidemiol. 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). 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]. Mol Psychiatry. 2019;3:51325. General cognitive ability ( g ), often referred to as 'general intelligence', predicts . Genome-wide association studies establish that human intelligence is highly heritable and polygenic. delayed recall of a story or a list of words, or a working memory test, such as backward digit span), visuo-spatial ability (such as the replication of a 2-dimensional pattern using blocks in the Wechsler Block Design test), and abstract reasoning (such as the inductive reasoning from abstract patterns that is required in Ravens Progressive Matrices). Gignac GE, Bates TC. Brothersister differences in the g factor in intelligence: analysis of full, opposite-sex siblings from the NLSY1979. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Transl Psychiatry. Genetics and intelligence differences: five special findings. Normative brain size variation and brain shape diversity in humans. Genetics and general cognitive ability. For example, should vertical pleiotropy drive the genetic correlation between intelligence and brain structure then it could indicate that brain structure is causal in intelligence differences; however the opposite scenario is possible, i.e. Is Intelligence Inherited? A Genetic Explanation Young AI, Frigge ML, Gudbjartsson DF, Thorleifsson G, Bjornsdottir G, Sulem P, et al. Friedman NP, Miyake A. A combined analysis of genetically correlated traits identifies 187 loci and a role for neurogenesis and myelination in intelligence.
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