You *could* use an F test to assess the variance of two groups, but the using F to test for differences in variance strictly requires that the distributions are normal.  Using Levene's test (i.e., absolute values of the deviations from the mean) is more robust, and using the [Brown-Forsyth test][1] (i.e., absolute values of the deviations from the *median*) is even more robust.  SPSS is using a good approach here.


  [1]: http://en.wikipedia.org/wiki/Brown%E2%80%93Forsythe_test