Csaba Csíkos: 1017 yearold students' judgments on proving strategies The focus of this study is the nature and development of reasoning processes (socalled proving ability) that allow for verifying logical statements. Students' judgments on different proofs of a given statement can be considered as important indicators of proving ability. In order to categorize different proof types, in this investigation proof concepts of philosophy, mathematics and jurisprudence are reviewed. Two tests of proving ability were administered to 1944 students from grades 5, 7, 9 and 11. The tests contained statements five different proofs that were categorized  based on Harel and Sowder's taxonomy  as authoritarian, ritual, symbolic, empirical and analytic. The proof types were constructed on the basis of a pilot study that set as an aim to let students allow writing many types of proofs to openended tasks. Students scored the different proofs on a fivepoint Likertscale. From the aspect of educational practice, the main results of this study are: (1) Fifthgraders accept authoritarian arguments more often than older children do. (2) In each age group, meaningless symbolmanipulation is overvalued. Even in case of nonmathematical content there is a tendency to give higher scores to meaningless symbolmanipulations. (3) In each age group, empirical proofs are relatively undervalued. Since students' judgments can largely be traced back to math teachers' bias towards symbolic proofs, mathematics can play an important role in fostering the development of proving ability. Practical considerations about the results of the present investigation may involve emphasizing the importance of 'exploring the territory' before proving a statement. Developmental tendencies revealed by crosssectional comparisons may be relevant for teacher educators and also for textbook writers and curriculum. MAGYAR PEDAGÓGIA 101. Number 3. 319345. (2001) Levelezési cím / Address for correspondence: Csíkos Csaba, Szegedi Tudományegyetem Pedagógiai Tanszék, H6722 Szeged, Petőfi S. sgt. 3034. 
