Cognitive interviewing evidence on DIF in Polytomous Items of the Student Questionnaire of the PISA Jose-Luis Padilla (jpadilla@ugr.es) University of Granada (Spain) Isabel BenÃtez Baena (ibenitez@ugr.es) University of Granada (Spain) M. Dolores Hidalgo (mdhidalg@um.es) University of Murcia (Spain) Stephen G. Sireci (sireci@acad.umass.edu) University of Massachusetts Amherst (USA) Paper presented at the 42th Annual Conference of the Northeastern Educational Research Association. Rocky Hill, CT (USA). October,19-21, 2011.