Genetics of Intelligence

European Journal of Human Genetics (2006) 14, 690–700

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Genetics of intelligence

Ian J Deary*,1, Frank M Spinath2 and Timothy C Bates1

1

Department of Psychology, University of Edinburgh, Edinburgh, UK; 2Differentielle Psychologie und Psychologische Diagnostik, Saarland University, Saarbruecken, Germany

This article provides an overview of the biometric and molecular genetic studies of human psychometric intelligence. In the biometric research, special attention is given to the environmental and genetic contributions to specific and general cognitive ability differences, and how these differ from early childhood to old age. Special mention is also made of multivariate studies that examine the genetic correlation between intelligence test scores and their correlates such as processing speed, birth weight and brain size. After an overview of candidate gene associations with intelligence test scores, there is a discussion of whole-genome linkage and association studies, the first of which have only recently appeared. European Journal of Human Genetics (2006) 14, 690 – 700. doi:10.1038/sj.ejhg.5201588

Keywords: IQ; intelligence; heritability; environment; twins; adoption

The phenotype

Intelligence was described by 52 researchers in the field as follows,1 Intelligence is a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience. It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather, it reflects a broader and deeper capability for comprehending our surroundings – ‘catching on,’ ‘making sense’ of things, or ‘figuring out’ what to do.

The structure of intelligence differences Despite over 100 years of concordant data, there is not widespread knowledge of the well-replicated...