Why do we differ in number sense? Evidence from a genetically sensitive investigation

Tosto, M.G.; Petrill, S.A.; Halberda, J.; Trzaskowski, M.; Tikhomirova, T.N.; Bogdanova, O.Y.; Ly, R.; Wilmer, J.B.; Naiman, D.Q.; Germine, L.; Plomin, R. and Kovas, Yulia. 2014. Why do we differ in number sense? Evidence from a genetically sensitive investigation. Intelligence, 43, pp. 35-46. ISSN 0160-2896 [Article]

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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 out Genome-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.

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Open Access funded by Medical Research Council.

We gratefully acknowledge the on-going contribution of the parents and children in the Twins Early Development Study (TEDS). TEDS is supported by a program grant [G0901245; previously G0500079] from the UK Medical Research Council; our work on environments and academic achievement is also supported by grants from the US National Institutes of Health [HD044454, HD046167 and HD059215]. RP's work is supported by a European Research Council Advanced Investigator Award [295366]. Research of MGT, YK, TNT and OYB is supported by a grant from the Government of the Russian Federation [grant 11.G34.31.0043]. We thank Professor Marco Zorzi for providing his insight into the neural network models.


Number sense; Mathematical ability; Behaviour genetics; Heritability; Directional selection

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March 2014Published

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10 Sep 2014 09:23

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29 Apr 2020 16:00

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Yes, this version has been peer-reviewed.



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