A multivariate quantitative-genetic analysis of behavioral development in mice.

The present experiment attempted a behavior-genetic dissection of early behavioral development in laboratory mice. To this end, we used a full, replicated diallel cross to uncover the genetical architecture as well as the multivariate genetic structure underlying early behavioral ontogeny. A number of standard sensorimotor tests were administered on postnatal Days 3, 5, 8, 10, 13, 17, and 22 to a total of 622 pups from 120 litters (4-6 pups per litter) from a four times replicated complete diallel cross between five inbred mouse strains. The first day on which an animal showed adult performance was taken as its score on that test. MANOVA did not show any effects of the pup's sex on the speed of development. Hayman's analysis of variance for diallel tables indicated no or only weak additive-genetic effects. Dominance was absent in almost all cases, except for the auricular startle response, where weak directional dominance for fast development was found. These results are in accordance with an evolutionary past of directional selection for well-canalized development. Factor analyses of the phenotypic and additive-genetic correlation matrices indicate that at least two factors are necessary to describe the behavioral variation.