标题:204 小学2年算数不振児の数概念の発達 (日本教育心理学会第4回総会部門別研究発表要旨・討論の概要 : 5. 学習・思考) [in Japanese] 204. The development of number concepts in the 2nd year underachievers in arithmetics. (TITLE OF PAPERS AND THE SUMMARIES OF DISCUSSIONS : 5. Learng and thinking) [in Japanese]