A Twin Study of the Genetics of High Cognitive Ability Selected from 11,000 Twin Pairs in Six Studies from Four Countries

“Two fit indices are reported: Dchi-squared (v(2)) and Akaike’s information criterion, (AIC; Akaike 1987).”

“IQ testing used the vocabulary and block design subtests of the age-appropriate WISC-III or WAIS-III.”

“His conclusion that ‘‘there is no escape from the conclusion that nature prevails enormously over nurture’’ ( Galton 1883, p. 241 ) was not warranted because his research involved family studies which cannot unambiguously disentangle the effects of nature and nurture and he used reputation as an index of ability.”

“These categorical data from each sample were used in Mx (Neale et al. 2006) to calculate tetrachoric twin correlations and thresholds, and to perform standard univariate liability-threshold modeling (Falconer 1965; Smith 1974).”

“In 1869, Francis Galton raised the topic of the etiology of high ability in one of the first books in behavioral genetics, Hereditary genius: An enquiry into its laws and consequences (Galton 1869).”

“However, the use of different measures and different samples can also be viewed as strengths because the results were nonetheless similar across the studies, which adds to the robustness of our conclusion that genetic variation contributes substantially to high g (Lykken 1968).”

“Standardized residuals were used because the age and sex of twins is perfectly correlated across pairs, and variation within age at the time of testing and variation within sex could contribute to the correlation between twins, and thus be misrepresented as environmental influences shared by the twins ( McGue and Bouc…”

“Zygosity was determined initially using a modified version of the Nichols and Bilbro (1966) questionnaire.”

“In a previous paper, we reported twin intraclass correlations for each sample and standard univariate twin model-fitting analyses using raw data (Haworth et al. 2009).”

“the well-documented extraordinary creative potential of this group (Lubinski and Benbow 2006; Lubinski et al. 2006).”

“Otherwise, the MCTFR sample is broadly representative of twin pairs born in Minnesota for the birth years sampled, with little evidence of participation bias in terms of parental education, socioeconomic status or mental health (Iacono et al. 1999).”

“The Netherlands Twin Register: Dutch Organization for Scientific Research (NWO 051.02.060; NWO 480-04-004; NWO 575-25-012; NWO/SPI 56-464-14192) and Human Frontiers of Science Program (RG0154/1998-”

“A substantial body of genetic research using the classical twin design has demonstrated the important role of genetics as a risk factor in the development of cognitive disabilities (Plomin and Kovas 2005).”

“questionnaire of physical similarity, which has been shown to be over 95% accurate when compared to DNA testing (Price et al. 2000).”

“It is our hope that finding substantial heritability for high g does not re-ignite controversies in relation to expert training (e.g., Howe et al. 1998).”

“The normal range of variation in g is the target of more genetic research than any other behavioral trait other than self-reported personality (Bouchard and McGue 1981; Deary et al. 2006; Plomin and Spinath 2004), but very little is known about the genetics of high cognitive ability.”

“The Twins Early Development Study (TEDS) is a sample of twins born in the UK between 1994 and 1996 (Oliver and Plomin 2007).”

“In the Introduction, we mentioned a hypothesis called emergenesis which suggests that exceptional cognitive ability may be due to epistasis, especially rare combinations of alleles (Lykken 1982, 2006).”

“Although these studies included different measures of cognitive ability, diverse cognitive tests can be used to create a g score that correlates highly with g scores derived from other tests (Johnson et al. 2008), which Charles Spearman (1927) referred to as the indifference of the indicator.”

“Although these studies included different measures of cognitive ability, diverse cognitive tests can be used to create a g score that correlates highly with g scores derived from other tests (Johnson et al. 2008), which Charles Spearman (1927) referred to as the indifference of the indicator.”

“The Twin Cognition Study (Luciano et al. 2003b) provides data for 338 MZ pairs and 513 DZ pairs (265 same-sex and 248 opposite-sex pairs), recruited through primary and secondary schools in the greater Brisbane area (Wright and Martin 2004).”

“The normal range of variation in g is the target of more genetic research than any other behavioral trait other than self-reported personality (Bouchard and McGue 1981; Deary et al. 2006; Plomin and Spinath 2004), but very little is known about the genetics of high cognitive ability.”

“wide association studies are underway (Kruglyak 2008) nearly all of these focus on diseases, disorders and the low end of distributions.”

“For the other pairs, zygosity was based on a series of physical similarity questions, answered by the mother of twins repeatedly over time (Rietveld et al. 2000).”

“IQ data at age 12 were collected in twins who took part in developmental studies of cognition and brain development (Bartels et al. 2002); IQ was assessed using the Dutch version of the WISC-R.”

“…Columbus, OH, USA D. Lubinski Department of Psychology and Human Development, Vanderbilt University, Nashville, TN, USA despite the societal importance of exceptional talent and the well-documented extraordinary creative potential of this group (Lubinski and Benbow 2006; Lubinski et al. 2006).”

“Further information about g as measured in TEDS can be found elsewhere (Davis et al. 2009; Haworth et al. 2007).”

“Further details of the ascertainment and history of the study are provided elsewhere (Rhea et al. 2006).”

“In 1869, Francis Galton raised the topic of the etiology of high ability in one of the first books in behavioral genetics, Hereditary genius: An enquiry into its laws and consequences (Galton 1869).”

“At age 18 the twins took part in studies of brain development and cognition (Rijsdijk et al. 2002); IQ was assessed using Raven’s standard progressive matrices and the Dutch version of the WAIS.”

“Support for the GHCA consortium members’ twin studies include: Western Reserve Reading Project (Ohio): US National Institute of Child health and Human Development (HD038075 and HD046167).”

“Further information about g as measured in TEDS can be found elsewhere (Davis et al. 2009; Haworth et al. 2007).”

“study reported that for cognitive abilities, but not for behavior problems, estimates of shared environment were more than twice as large for twins as compared to non-twin siblings (Koeppen-Schomerus et al. 2003).”

“In the Introduction, we mentioned a hypothesis called emergenesis which suggests that exceptional cognitive ability may be due to epistasis, especially rare combinations of alleles (Lykken 1982, 2006).”

“The adult twins had also taken part in a study of brain function and IQ (Posthuma et al. 2002), where IQ was assessed using the Dutch WAIS.”

“Individuals ranged from 6 to 71 years of age and the samples are organized here in order of the average age of the sample.”

“For these reasons, in collaboration with Martha Putallaz at Duke University, the consortium has launched a study of participants in the talent identification program (TIP; Putallaz et al. 2005).”

“IQ data were available in twins who had taken part in studies on cognition at ages 6, 12 and 18 years (Boomsma et al. 2008) or as adults.”

“Three reports of a few dozen twins of high ability in infancy (Petrill et al. 1998), childhood (Plomin and Thompson 1993), and in later life (Saudino et al. 1994), found substantial genetic influence and moderate shared environment (environmental effects that make members of the same family more…”

“Other studies have investigated the etiology of individual differences within high-g groups, with mixed results (Thompson et al. 1993); however, such studies ask why high-ability individuals differ from each other in their g scores rather than asking why high-ability individuals as a group have so…”

“Three reports of a few dozen twins of high ability in infancy (Petrill et al. 1998), childhood (Plomin and Thompson 1993), and in later life (Saudino et al. 1994), found substantial genetic influence and moderate shared environment (environmental effects that make members of the same family more…”

“The Twin Cognition Study (Luciano et al. 2003b) provides data for 338 MZ pairs and 513 DZ pairs (265 same-sex and 248 opposite-sex pairs), recruited through primary and secondary schools in the greater Brisbane area (Wright and Martin 2004).”

“Three reports of a few dozen twins of high ability in infancy (Petrill et al. 1998), childhood (Plomin and Thompson 1993), and in later life (Saudino et al. 1994), found substantial genetic influence and moderate shared environment (environmental effects that make members of the same family more…”

“The Minnesota Center for Twin and Family Research ( Iacono et al. 2006 ) provides data for 1,177 MZ pairs and 679 same-sex DZ pairs.”

“The Twin Cognition Study (Luciano et al. 2003b) provides data for 338 MZ pairs and 513 DZ pairs (265 same-sex and 248 opposite-sex pairs), recruited through primary and secondary schools in the greater Brisbane area (Wright and Martin 2004).”

“The only large twin study of high g was selected from a sample of 1,943 young twin pairs (2, 3 and 4 years) assessed by their parents (Ronald et al. 2002).”

“…than would be expected by sampling variability alone.1 We also replicated the well-established phenomenon that genetic influences on intelligence increase and shared environmental influences on intelligence decrease with childhood age (e.g., Briley & Tucker-Drob, 2013; Haworth et al., 2009).”

“Note that the United Kingdom is unique in its use of the term learning disabilities to refer to individuals with a significantly reduced ability to understand new or complex information and to learn new skills (impaired intelligence) as well as a reduced ability to cope independently (impaired social functioning).”

“Both cognitive ability and violent criminality are heritable [26,27,44], so individuals with lower cognitive ability and convictions for violent offending are at increased risk of having parents with the same characteristics.”

“The few genetic studies on high performance, in contrast to normal or low performance, have focused primarily on high intelligence (Haworth et al., 2009).”

“…model-fitting yielded evidence supporting the Continuity Hypothesis because estimates of genetic influence did not differ for high intelligence (0.50 with a 95% confidence interval of 0.41 to 0.60) and the entire sample (0.55; 0.51–0.59) (Haworth, Dale, & Plomin, 2009; Haworth et al., 2009).”

“Although no difference was reported in the etiology of individual differences (Haworth et al., 2009; cross-sectional Genetics of High Cognitive Ability, or GHCA, Consortium sample) or in their trajectories of developmental change (Brant et al., 2009; Longitudinal Twin Sample), these investigations…”

“Indeed, mainstream thought on academic achievement and related concepts (such as giftedness and academic aptitude) is that environmental influences on a child have an undeniable impact on the observed levels of academic and cognitive traits and that traits cannot be measured in isolation of the environment’s impact on…”

“In effect, the heritability of intelligence is estimated to be somewhere between 30% to over 80% in classical MZ twin versus dizygotic twin studies [3–5], marking it one of the highest among human quantitative traits.”

“In a well-powered analysis using data from 11,000 twin pairs, (Haworth et al., 2009) investigated genetic and nongenetic influences on g for the top 15% of the distribution and found substantial contribution of genetic variation whereas influence of shared environmental effects for high cognitive abilities was only mo…”

“…the genetic influence to be largely, if not entirely, additive for high intelligence as well as the entire distribution of intelligence (see also Plomin & Haworth, 2009) – although small or rare non-additive effects cannot be definitely ruled out due to the lack of statistical power to detect them.”

“In humans for instance, statistical settings based on twins are used similarly to cross-fostering experiments to estimate the heritability of traits such as cognitive capacity [53,54].”

“Previous studies have demonstrated that both cognitive ability and personality traits are partially heritable (Deary, Spinath, & Bates, 2006; Haworth et al., 2009; Jang, Livesley, & Vernon, 1996; Loehlin, McCrae, Costa, & John, 1998). Political socialization is yet another potential confounding variable. Family experi…”

“We should note that researchers have consistently found that cognitive ability is heritable (Dawes et al., 2014; Haworth et al., 2009; Oskarsson et al., 2015, 2012; Weinschenk et al., 2017).”

“It is notable that such erosion in MZ twin similarity is not observed, by way of example, for supranormal intelligence, when examined among identical twins [4].”

“We refer to Haworth et al. (2009) and the references therein, for a detailed overview of the IQ test batteries used in the different studies.”

“A large body of work comparing monozygotic and dyzygotic twin sets indicates that approximately half of the variation in human intelligence as measured by standard tests is genetic, with estimates ranging between 40 and 80% [1,2,3,4,5,6].”

“Cross-sectional and longitudinal twin studies have consistently shown strong genetic influences on cognitive performance, in both normal variation and in the extremes of the normal distribution [1,2].”

“Additionally, research in psychology has demonstrated that many personality traits, including the Big Five, are partially heritable (Deary, Spinath, & Bates, 2006; Haworth et al., 2009; Jang, Livesley, & Vernon, 1996; Loehlin, McCrae, Costa, & John, 1998), as is educational attainment (Branigan, McCallum, & Freese, 20…”

“Previous studies on the zygosity differences in IQ from childhood through early adulthood have shown mixed results, with higher, similar, and lower IQ in MZ twins as compared with DZ twins without a clear age pattern (Haworth et al., 2009; Keller et al., 2013; Modig et al., 2011; Silventoinen et al., 2006).”

“Combining data from four countries to create a larger sample than all previous studies of the genetics of cognitive abilities combined, Haworth et al. (2010) recently analyzed data from 11,000 twin pairs from six samples in four countries (Australia, the Netherlands, the United Kingdom, and the United States) to test…”

“Он рассматривает биологический интеллект как генетически детерминированную биологическую базу когнитивного функционирования и всех его индивидуальных различий [13, 38].”

“These subtests were selected because the resulting IQ score correlates highly with the total IQ score based on all WAIS subtests (Haworth et al. 2009).”

“…have shown that individual differences in most human traits such as those mentioned above (intelligence, motivation, personality, social cognition, and psychopathology) are, at least to a moderate extent, due to genetic factors (Greven et al. 2009; Haworth et al. 2009; Petrill et al. 2009).”

“Moreover the heritability of some cognitive abilities increases over childhood [7].”

“%) in 11,000 twin pairs aged 6–71, recruited from four countries (Haworth et al., 2009).”