Factor analysis shows that female rat behaviour is characterized primarilyby activity, male rats are driven by sex and anxiety

This experiment explored sex differences in behaviour using factor analysis to describe the relationship between different behavioral variables. A pri ncipal component solution with an orthogonal rotation of the factor matrix was used, ensuring that the extracted factors are independent of one anothe r, and thus reflect separate processes. In the elevated plus-maze test of a nxiety, in male rats factor 1 accounted for 75% of the variance and reflect ed anxiety, factor 2 represented activity, and accounted for 24% of the var iance. This contrasted with the finding in female rats in which factor 1 wa s activity, accounting for 57% of the variance, with the anxiety factor acc ounting for only 34% of the variance. When behaviour in both the plus-maze and holeboard were analysed, a similar sex difference was found with anxiet y emerging as factor 1 in males and holeboard activity as factor 1 in femal es. Locomotor activity in the inner portion of the holeboard loaded on the anxiety factor for males, but on activity for females. When behaviours in t he plus-maze and sexual orientation tests were analysed, anxiety emerged as factor 1 in males, sexual preferences factor 2, and activity factor 3. In females, activity was factor 1, sexual preference factor 2, anxiety factor 3, and social interest factor 4. These results suggest caution should be ex ercised in interpreting the results from female rats in tests validated on males because the primary controlling factor may be different. (C) 1999 Els evier Science Inc.