More and more, education programs from many countries consider Critical Thinking (CT) to be an essential 21 st century competency. Our conception of CT corresponds to a socio-constructivist epistemology and the context of our research is situated in the Philosophy for Children approach. This text presents a study, in which we compared results from two exchanges, one which was conducted with closed anecdotal-type questions, and the other with open philosophically-oriented questions. The analysis tool was the operational model of the developmental process of Dialogical Critical Thinking (DCT), developed and validated in previous studies. Participants were five groups of Moroccan pupils aged 10 to 15 years. Results indicate that in the exchange conducted with closed anecdotal-type questions, the overall epistemol-ogy of groups of pupils aged 10 to 15 years was simple, and the dominant epis-temological perspective was post-egocentricity. In the exchange conducted with open philosophically-oriented questions, the overall epistemology for the majority of pupil groups was simple with a tendency toward a complex epistemol-ogy, and the dominant perspective for the majority of groups was relativism.