Abstract: In our experiment we collected protocols from subjects who were solvinggeometrical problem and analyzed them from the point of view of cognitivepsychology. The result shows that:correct and quick recognition of the patterns whichaccesses the necessary knowledge in permanent memory is the key in solvinggeometrical problems. The difference between the students with more experience and those withless experience is that the former recognized patterns more quickly andcorrectly than the latter whose activity showed more trial and error approaches;the former could,in some cases,keep away from interferences,while thelatter suffered from them easily;the former were able to combine variousrelated information for their reasoning while the latter utilized the informa-tion in isolation;the former could trade-off between backward and forwardsearches,while the latter were poor at using backward search.

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