Psychological Collaboration in Kyoto University of Education has researched into developmental process of knowledge systematization. The present reports are the parts of the research series. REPORT VIII The Longitudinal Analysis of a Test for Structure of Thinking Operation. Thinking Structure Test has been administered longitudinally to children from 1968(Group A: from kindergarten to second grade, Group B: from second grade to fourth grade). The test consists of items which are devised to measure the achievement level of "concrete operations" with reference to the experiments by Piaget. It includes four groupments and two concepts; addition of classes, multiplication of classes, addition of relations, multiplication of relations, space concept and conservation. Through longitudinal analysis of the data, we found out the following points:(1)The developmental rate, at which children enter into concrete the operation stage from the intuitive stage, has not much correlation with the rate at which they grow to complete their operations through the concrete operation stage.(2)We found the two types of processes in which children systematized multiplicational operation of relations and conservation; the one, completion of multiplicational operation precededs to formation of conservation, the other, conversely, formation of conservation proceedes to completion of the multiplicational operation.(3)In Group A, the children, who had tended to complete the multiplication operation of relations earlier, showed more gains in test scores for two years, than the children who had completed it later. (4)We devised a new factorial approach, analizing the correlations between each operation(or concept)which indicated co-changeability in respect to progress or stagnation of each operation for the given period. The results suggested that co-changeability between logical and infralogical structure development was not so high. This approach, thought it is a tentative one, may be an effective technique for analysing longitudinal data in future research. REPORT IX Longitudinal Investigation on the Development of Social Concept "War" In the course of our study on concept formation, we have adopted several concepts in respect to social studies. The present report is based on a longitudinal analysis of the concept "war". Thirty-one kindergartener were asked to answer "Do you know war? What does it mean? How does it come about?" After two years, the same questions were repeated to the same children who were in second grade. We have come to find out that these who showed a better answer in second grade, had mentioned richer iconic images of "War" on the test in kindergartener-age. The kindergartener who had given superficial verbal definition of war earlier, did not show so much progress afterwards. The degree of progress in concept formation by each child was coincident with the one in his score of Thinking Structure Test. REPORT X Preparing to Test for Thinking Structure in Verbal Form. We made up a Thinking Structure Test in verbal form to measure developmental process from concrete operation to formal operation stage. The Test, consists of 23 verbal questions involving operations of formal logic with reference to A. Morf's questions, was administered to children from third grade to ninth grade. We examined cross-sectionally percentage of right answers of each item and could predict the developmental sequence of formal operation; the disjunction form was easier, the incompatibility and implication forms were more difficult.