Strain and sex differences in the degree of paw preference in mice.

The direction and degree of paw preference was studied in male and female mice from the C3H/He, C3H/OuJIco and New Zealand Black (NZB) strains, using the method previously described by Collins. All the populations of mice tested exhibited a low degree of lateralization, which varied among strains: NZB mice were more strongly lateralized than both C3H substrains; C3H/He had a higher degree of lateralization than C3H/OuJIco mice. Females tended to be more strongly lateralized than males, particularly in the C3H/He mice. No direction bias was observed in the strains tested, as lateralized mice were equally distributed into left-and right-handers. The distributions of paw preference found in the strains tested in this study are different from those obtained by Collins in C57BL/6J mice, in that most of his animals were strongly lateralized and only a few were ambidextrous. These strain differences in the degree of paw preference may be explained by genetic factors or differential rearing histories, which are known to influence the development of brain asymmetries.