Why do we differ in number sense? Evidence from a genetically sensitive investigation.
Basic intellectual abilities of quantity and numerosity estimation have been detected across animal species. Such abilities are referred to as 'number sense'. For human species, individual differences in number sense are detectable early in life, persist in later development, and relate to general intelligence. The origins of these individual differences are unknown. To address this question, we conducted the first large-scale genetically sensitive investigation of number sense, assessing numerosity discrimination abilities in 837 pairs of monozygotic and 1422 pairs of dizygotic 16-year-old twin pairs. Univariate genetic analysis of the twin data revealed that number sense is modestly heritable (32%), with individual differences being largely explained by non-shared environmental influences (68%) and no contribution from shared environmental factors. Sex-Limitation model fitting revealed no differences between males and females in the etiology of individual differences in number sense abilities. We also carried outGenome-wide Complex Trait Analysis(GCTA) that estimates the population variance explained by additive effects of DNA differences among unrelated individuals. For 1118 unrelated individuals in our sample with genotyping information on 1.7 million DNA markers, GCTA estimated zero heritability for number sense, unlike other cognitive abilities in the same twin study where the GCTA heritability estimates were about 25%. The low heritability of number sense, observed in this study, is consistent with the directional selection explanation whereby additive genetic variance for evolutionary important traits is reduced.
Department of Psychology, University of York, Heslington, York YO10 5DD, United Kingdom ; Department of Psychology, Tomsk State University, 36 Lenin Prospekt, 634050, Tomsk, Russia.
M G
MG
Tosto
The Ohio State University, Columbus, OH 43210, United States.
S A
SA
Petrill
Department of Psychological and Brain Sciences, The Johns Hopkins University, Baltimore, MD 21218-268, United States.
J
J
Halberda
King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, United Kingdom.
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M
Trzaskowski
Department of Psychology, Tomsk State University, 36 Lenin Prospekt, 634050, Tomsk, Russia.
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TN
Tikhomirova
Department of Psychology, Tomsk State University, 36 Lenin Prospekt, 634050, Tomsk, Russia.
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OY
Bogdanova
Department of Psychological and Brain Sciences, The Johns Hopkins University, Baltimore, MD 21218-268, United States.
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R
Ly
Department of Psychology, Wellesley College, Central Street, Wellesley, MA 02481, United States.
J B
JB
Wilmer
Department of Psychological and Brain Sciences, The Johns Hopkins University, Baltimore, MD 21218-268, United States.
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DQ
Naiman
Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, United States.
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L
Germine
King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, United Kingdom.
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R
Plomin
Department of Psychology, Tomsk State University, 36 Lenin Prospekt, 634050, Tomsk, Russia ; King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, United Kingdom ; Goldsmiths, University of London, London SE14 6NW, United Kingdom.
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Kovas
Behaviour genetics; Directional selection; Heritability; Mathematical ability; Number sense