Resolving the genetic and environmental sources of the correlation between height and intelligence: a study of nearly 2600 Norwegian male twin pairs.

The main aim of this paper was to resolve the correlation between intelligence test scores and standing height into genetic and environmental components. Data on 1181 identical and 1412 fraternal twin pairs (all males) were retrieved by matching files from the Norwegian Army with twin registries. The data were analyzed by means of a structural equation model comprising latent genetic, shared environmental and nonshared environmental factors and correlations between them. A major part of the height--intelligence correlation was due to correlated shared environments (59% of the phenotypic height--intelligence correlation), but statistically significant effects of correlated genes and nonshared environments were also found (respectively 35% and 6% of the phenotypic correlation).