the gene frequencies at trait-relevant loci rather than genetic drift due to the necessarily small population sizes. The main advantage of selective breeding is that any other traits that differ in the divergently selected lines are presumably due to pleiotropic influences of the genes affecting the selection phenotype. These are called genetically correlated responses to selection, and should offer clues to the neurobiology of the trait of interest. Discussions of the technical requirements for interpreting selection studies for behavioral traits have been published (Crabbe et al. 1990; Crabbe 1999; Henderson 1989).
