Statements taught to students can, in general, be described in proposition form, as "if it is p, then it implies q." Instances where the antecedent "p" is illustrated are known as substitution instances. In addition, it is possible to obtain another type of instances by illustrating the consequent "q." We will refer to this type of instances as symbolic instances. The aim of this study is to clarify the condition under which symbolic instances can have a positive effect on learning. We focused in our study on the teaching of history. We prepared three different texts that involved one of three symbolic instances concerning the Meiji era. Each text was presented to one of three groups of undergraduate participants in the learning session of the experiment. After the learning session, we presented them with a problem to which learners had previously given an incorrect answer due to their misconception. The problem could be solved correctly by referring to the symbolic instance presented in the learning session. In addition, we asked the participants to specify whether they had referred to the symbolic instance at the time of problem solving, and if they had not, to explain their reasons for failing to do so. We found that failure to refer to the instance had two causes: the symbolic instance had been given a different interpretation or the subjects had been unable to incorporate it into their cognitive structure. However, the symbolic instances that could be incorporated into learners' cognitive structure easily and did not allow another interpretation were effective. In the second experiment, we presented learners with two symbolic instances simultaneously. This treatment was revealed to be very effective in correcting learners' misconception.

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Children and adults know that when sunlight converges with a convex lens, it makes a small round dot. They, however, tend to think that no other light than sunlight (e.g., from a fluorescent lamp) can converge with a convex lens, and that even if a fluorescent light converged it would form a small round dot. These facts perplex us because in junior high school, students learn that when a light converges with a convex lens, it forms an image of an object that emits or reflects the light. Analyzing science textbooks in junior high school, we found that the textbook emphasized the manner in which the size and position of the reflected image is modified by changes in the position of the source. We considered the possibility that this mode of presentation made it difficult for students to grasp the mechanism of image formation per se. In study 1, university students (N=28) were divided into two groups. After the explanation of an experiment using a convex lens and a candle, the rule per se was emphasized to one group (group 1), and the place and the size of the image were emphasized to the other group(group 2). The target problem was as follows; "Does the light from a fluorescent ceiling lamp converge with a convex lens, and if so, what will you see on the screen-" Although the number of students in Group 1 who gave a correct answer was higher than the corresponding number in Group 2, the overall score in Group 1 was not very high. In study 2, university students (N=48) were asked to draw the path of the light and the shapes of the images projected on a screen when different light sources were used. In spite of the fact that the rule was emphasized to them, their performance did not improve. In study 3, we asked the subjects in study 2 why it was difficult for them to apply the rule to the target problem. Analysis of their answers revealed their misconceptions. Some thought that only parallel light rays like the sun's could converge. Others thought that the small round dot which a convex lens made when sunlight converged was not the image of the sun. The article examines the manner in which these results can be used to improve the efficiency of science teaching for this topic.

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The purpose of this study was to design an intervention strategy which induces changes from naive theories regarding 'conservation of mass in a water solution' to scientific theories through collaborative discussion during observation and experimentation sessions of the dissolution of substances in a fifth-grade science class, and then to examine the effects. Results of a descriptive analysis of pre-post tests and interactive analysis of verbalization activity showed that: 1) the teacher's revoicing, which coordinates prediction, date and theory, generates transactive discussion in the direction of learning towards 'self-transforming modes'; 2) the teacher's revoicing, which clarifies inconsistencies among theories of members and then reformulates the theories, generates transactive discussion in the direction of learning towards 'other-transforming modes'. These findings suggested that transactive discussion in 1) and 2) causes cooperative construction of theories.

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