Genetics and intelligence differences: five special findings

R. Plomin*, I. J. Deary

*Corresponding author for this work

Research output: Contribution to journalLiterature reviewpeer-review

Abstract

Intelligence is a core construct in differential psychology and behavioural genetics, and should be so in cognitive neuroscience. It is one of the best predictors of important life outcomes such as education, occupation, mental and physical health and illness, and mortality. Intelligence is one of the most heritable behavioural traits. Here, we highlight five genetic findings that are special to intelligence differences and that have important implications for its genetic architecture and for gene-hunting expeditions. (i) The heritability of intelligence increases from about 20% in infancy to perhaps 80% in later adulthood. (ii) Intelligence captures genetic effects on diverse cognitive and learning abilities, which correlate phenotypically about 0.30 on average but correlate genetically about 0.60 or higher. (iii) Assortative mating is greater for intelligence (spouse correlations similar to 0.40) than for other behavioural traits such as personality and psychopathology (similar to 0.10) or physical traits such as height and weight (similar to 0.20). Assortative mating pumps additive genetic variance into the population every generation, contributing to the high narrow heritability (additive genetic variance) of intelligence. (iv) Unlike psychiatric disorders, intelligence is normally distributed with a positive end of exceptional performance that is a model for 'positive genetics'. (v) Intelligence is associated with education and social class and broadens the causal perspectives on how these three inter-correlated variables contribute to social mobility, and health, illness and mortality differences. These five findings arose primarily from twin studies. They are being confirmed by the first new quantitative genetic technique in a century-Genome-wide Complex Trait Analysis (GCTA)-which estimates genetic influence using genome-wide genotypes in large samples of unrelated individuals. Comparing GCTA results to the results of twin studies reveals important insights into the genetic architecture of intelligence that are relevant to attempts to narrow the 'missing heritability' gap.

Original languageEnglish
Pages (from-to)98-108
Number of pages11
JournalMolecular Psychiatry
Volume20
Issue number1
Early online date16 Sep 2014
DOIs
Publication statusPublished - Feb 2015

Keywords

  • GENOME-WIDE ASSOCIATION
  • GENERAL COGNITIVE-ABILITY
  • CAUSE-SPECIFIC MORTALITY
  • COMMON SNPS EXPLAIN
  • OLD-AGE
  • ENVIRONMENTAL-INFLUENCES
  • INCREASING HERITABILITY
  • INDIVIDUAL-DIFFERENCES
  • SOCIOECONOMIC-STATUS
  • COMPLEX DISEASES

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