[Air-l] How can we identify critical thinkers in the sample of a research project?

Dear colleagues I am in the middle of designing a questionnaire to get information about the sample of my study (Phd degree). In addition to obtaining all necessary demographic information I also need to find out about their previous critical reflection experiences-if any- so that I can identify the critical thinkers in my sample. Would anyone have any knowledge or ideas on how can I identify this via the questionnaire method and/or related theory-critical reflection indicators? Many thanks. Kate Pavlidou aikaterini.pavlidou@durham.ac.uk