Old and new ideas about genes and behaviour

Many kinds of common mental deficiencies such as senile dementia have a heterogeneous background, and so have normal variations in talents and personality. The mapping of the human genome, the availability of an unlimited number of genetic markers and efficient statistical tools promised ample discoveries of genes behind the variation. The expectations have not been fulfilled and more subtle influences on gene expression have to be assumed. Topics that are taken up include genomic imprinting, brain activation patterns, the importance of neurotransmitter regulation and non-additive interactions between genes and environment.