Sex differences in the emotional behaviour of laboratory mice

Three laboratory strains of mice (C57, BALB/c, Porton) were tested in an open field using a number of measures taken during the initial 2 min of testing and after a loud bell had sounded. The mice were tested either in a clean field or in one containing an odour of a same-sex conspecific. Over all three strains, several measures indicated that females showed high leveles of 'emotional' or 'fear' responses than did males. This sex difference was found in C57 and BALB/c strains but not in the Portons; it could not be attributed to activity or response-specific sex differences. Conspecific odours did not influence the direction of the main findings.