Genetic effects on Intelligence and Personality

Pedigree-based analyses found that genetic differences account for 50–80% of the variation of observable (phenotypic) traits. Personality traits account for 34–48% of the variance being explained by genetic differences. Molecular genetic studies have also found that intelligence and personality variables are heritable by 30% and 0-15% respectively. These types of studies may differ because platforms operating genetic makeup are poor at tagging causal, low minor allele frequency, copy number and structural variants. A group genotyped for ~700,000 single-nucleotide polymorphisms (SNPs) was used in order to exploit the high levels of linkage disequilibrium (LD) found in people who are related to evaluating the total effect of genetic variants that are not observable in unrelated individuals. Genetic variants in low LD with SNPs in their genetic makeup explain more than half of the genetic variance in intelligence, education, and neuroticism. These additional genetic effects will aid in approximating the heritability estimates from twin studies for intelligence and education, but not for neuroticism and extraversion. Our findings are then replicated using assigned molecular genetic data from unrelated individuals to show that ~50% of differences in intelligence, and ~40% of the differences in education, can be explained by genetic effects when a larger number of rare SNPs are present. An evolutionary genetic perspective states that a large addition of rare genetic variants to individual differences in intelligence, and education is consistent with a balance of mutation and selection.

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