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Author: Cabeza de Baca, Tomas
Resulting in 1 citation.
1. Woodley, Michael A.
Reeve, Charlie L.
Kanazawa, Satoshi
Meisenberg, Gerhard
Fernandes, Heitor B.F.
Cabeza de Baca, Tomas
Contemporary Phenotypic Selection on Intelligence is (mostly) Directional: An Analysis of Three, Population Representative Samples
Intelligence 59 (November-December 2016): 109-114.
Cohort(s): NLSY79
Publisher: Elsevier
Keyword(s): Armed Services Vocational Aptitude Battery (ASVAB); Britain, British; Fertility; Gender Differences; I.Q.; Project Talent; Racial Differences

Three large and nationally representative datasets (NCDS, N = 5225, NLSY79, N = 7598 and Project Talent, N = 76,150) are here examined in order to determine if models incorporating negative quadratic effects of IQ on fertility (which would indicate the presence of stabilizing phenotypic selection) improve model fit, relative to ones that only consider linear effects (which indicate directional phenotypic selection). Also considered were possible interactions among these terms and sex and race. For two datasets (NCDS and NLSY79) the best fitting models did not include quadratic terms, however significant sex*IQ and race*IQ interactions were found respectively. Only in Project Talent did the inclusion of a quadratic effect (along with IQ*sex and IQ2* sex interactions) yield the best-fitting model. In this instance a small magnitude, significant negative quadratic term was found in addition to a larger magnitude linear term. Post hoc power analysis revealed that power was lacking in the two smaller samples (NCDS and NLSY′79) to detect the quadratic term, however the best fitting and most parsimonious models selected for these datasets did not include the quadratic term. The quadratic terms were furthermore several times smaller in magnitude than the linear terms in all models incorporating both terms. This indicates that stabilizing phenotypic selection is likely only very weakly present in these datasets. The dominance of linear effects across samples therefore suggests that phenotypic selection on IQ in these datasets is principally directional, although the magnitude of selection is relatively small, with IQ explaining at most 1% of the variance in fertility.
Bibliography Citation
Woodley, Michael A., Charlie L. Reeve, Satoshi Kanazawa, Gerhard Meisenberg, Heitor B.F. Fernandes and Tomas Cabeza de Baca. "Contemporary Phenotypic Selection on Intelligence is (mostly) Directional: An Analysis of Three, Population Representative Samples." Intelligence 59 (November-December 2016): 109-114.