Generally speaking, the language used in cognitive assessments is biased toward midwestern dialects, which historically was considered broadcast English (though the locus of broadcast/standard English appears to have shifted further west over the years). Some even have recorded listening selections, which are definitely biased toward midwestern pronunciation. I have heard some amusing regional usages reflected in answers. Actually, I once wrote to a test author (not of the WISC) to ask for suggestions to address a regional difference that was so pervasive that it was a rarity for a child to provide the "correct" answer--and he actually responded with alternate scoring!
