Spatial ability and spatial memory in high school students with different levels of mathematical fluency.

The study investigated spatial ability and visuo-spatial memory in groups of high school students with different levels of mathematical fluency. We used the Mental Rotation Task and Corsi Block-Tapping Task to measure spatial ability and visuo-spatial memory, respectively. A statistically significant difference was found between the groups with different levels of math fluency in terms of effectiveness of spatial ability and level of visuo-spatial memory. Statistically significant sex differences were observed in levels of spatial ability and visuo-spatial memory: males showed better results than females. However, sex explained only between 1 and 3% of the variation in these abilities

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 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