1. ¹Department of Psychology, University of Edinburgh, Edinburgh, UK
2. ²Differentielle Psychologie und Psychologische Diagnostik, Saarland University, Saarbruecken, Germany

Correspondence: Professor IJ Deary, Department of Psychology, University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, Scotland, UK. Tel: +44 0 131 650 3452; Fax: +44 0 131 651 1771; E-mail: I.Deary@ed.ac.uk

Received 19 August 2005; Revised 14 December 2005; Accepted 15 December 2005.

Abstract

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.