Twin Studies of General Mental Ability

Segal, Nancy L.; Johnson, Wendy

doi:10.1007/978-0-387-76727-7_6

Cited by 9 publications

(8 citation statements)

References 116 publications

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“…It is an ongoing matter of debate as to how to classify this covariance in the calculation of heritability; certainly many, if not most, scholars would agree that it fits neatly in neither the G nor the E category. Several behavioral geneticists have argued that such gene-environment correlations should be classified as genetic effects (e.g., Fowler, Baker, and Dawes, 2008;Segal and Johnson, 2009); however, as Rutter (2002: 4) noted, "it is misleading to suppose that just because genetic factors influence the occurrence of an environmental risk factor, this must mean that the risk process is genetically mediated. This assumption does not follow because there is no necessary connection between the causes of the origin of a risk factor and its mode of risk mediation."…”

Section: Conceptual Problem: (The Fallacy Of) Partitioning Genetic Anmentioning

confidence: 99%

Pulling Back the Curtain on Heritability Studies: Biosocial Criminology in the Postgenomic Era

Burt

Simons

2014

Criminology

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Section: Conceptual Problem: (The Fallacy Of) Partitioning Genetic Anmentioning

confidence: 99%

Pulling Back the Curtain on Heritability Studies: Biosocial Criminology in the Postgenomic Era

Burt

Simons

2014

Criminology

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“…Other twin studies including one in Russia (Malykh et al, 2005). For a recent review of twin studies, see Segal and Johnson (2009) and for recent studies, see (Bratko et al, 2010; Davis et al, 2009). Very large studies that include both twin and singleton data (Calvin et al, 2012).…”

mentioning

confidence: 99%

The Wilson Effect: The Increase in Heritability of IQ With Age

Bouchard

2013

Twin Res Hum Genet

125

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Ronald Wilson presented the first clear and compelling evidence that the heritability of IQ increases with age. We propose to call the phenomenon 'The Wilson Effect' and we document the effect diagrammatically with key twin and adoption studies, including twins reared apart, that have been carried out at various ages and in a large number of different settings. The results show that the heritability of IQ reaches an asymptote at about 0.80 at 18-20 years of age and continuing at that level well into adulthood. In the aggregate, the studies also confirm that shared environmental influence decreases across age, approximating about 0.10 at 18-20 years of age and continuing at that level into adulthood. These conclusions apply to the Westernized industrial democracies in which most of the studies have been carried out.

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“…It is an ongoing matter of debate as to how to classify this covariance in the calculation of heritability; certainly many, if not most, scholars would agree that it fits neatly in neither the G nor the E category. Several behavioral geneticists have argued that such gene–environment correlations should be classified as genetic effects (e.g., Fowler, Baker, and Dawes, ; Segal and Johnson, ); however, as Rutter (: 4) noted, “it is misleading to suppose that just because genetic factors influence the occurrence of an environmental risk factor, this must mean that the risk process is genetically mediated. This assumption does not follow because there is no necessary connection between the causes of the origin of a risk factor and its mode of risk mediation.” This can be illustrated with real‐world examples such as skin pigmentation (Billings, Beckwith, and Alper, ; Joseph, ).…”

Section: Heritability Studiesmentioning

confidence: 99%

Pulling Back the Curtain on Heritability Studies: Biosocial Criminology in the Postgenomic Era

2014

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Unfortunately, the nature-versus-nurture debate continues in criminology. Over the past 5 years, the number of heritability studies in criminology has surged. These studies invariably report sizeable heritability estimates (∼50 percent) and minimal effects of the so-called shared environment for crime and related outcomes. Reports of such high heritabilities for such complex social behaviors are surprising, and findings indicating negligible shared environmental influences (usually interpreted to include parenting and community factors) seem implausible given extensive criminological research demonstrating their significance. Importantly, however, the models on which these estimates are based have fatal flaws for complex social behaviors such as crime. Moreover, the goal of heritability studies-partitioning the effects of nature and nurture-is misguided given the bidirectional, interactional relationship among genes, cells, organisms, and environments. This study provides a critique of heritability study methods and assumptions to illuminate the dubious foundations of heritability estimates and questions the rationale and utility of partitioning genetic and environmental effects. After critiquing the major models, we call for an end to heritability studies. We then present what we perceive to be a more useful biosocial research agenda that is consonant with and informed by recent advances in our understanding of gene function and developmental plasticity.Questions about nature versus nurture have been a perennial topic of debate in the social sciences. Since the 1970s, these questions have been addressed by a field of study known as behavioral genetics. A major focus of behavioral genetics research has been to partition the variation in an outcome of interest into a proportion caused by genes (heritability) and a proportion caused by the environment (e.g., DiLalla, 2004;Plomin et al., 2012). These heritability studies (also called quantitative genetics, nonmolecular genetics, or biometrics) have compared phenotypes (observed characteristics of individuals) within

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Twin Studies of General Mental Ability

Cited by 9 publications

References 116 publications

Pulling Back the Curtain on Heritability Studies: Biosocial Criminology in the Postgenomic Era

Pulling Back the Curtain on Heritability Studies: Biosocial Criminology in the Postgenomic Era

The Wilson Effect: The Increase in Heritability of IQ With Age

Pulling Back the Curtain on Heritability Studies: Biosocial Criminology in the Postgenomic Era

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