The purpose of this study was to investigate the developmental processes of mental operations, as a competence factor for Bayesian reasoning on a drawing-of-lots problem. The main results were as follows. First, junior high school students passed only problems with a first-order quantification of probability (Nakagaki, 1989), while university students were able to pass problems with a second-order quantification of probability. Next, "likelihood neglect" was apparent in participants' responses rather than "base-rate neglect." Finally, participants did not appear to use the representativeness heuristic in their reasoning (Tversky & Kahneman, 1974), and even university students lacked competence in Bayesian reasoning (third-order quantification of probability).

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This case study focused on the development of postural dynamics for reaching by an infant from a prone position. This transitional process was examined from a functional perspective. A total of 155 acts of reaching from a prone position were observed on 9 separate days between the ages of 5 and 8 months, and were analyzed from both quantitative and qualitative points of view. First, all acts were classified into three types, based on whether each reaching act had the function of supporting the upper body. The frequency and rate of appearance of each type were analyzed quantitatively for the nine days. Second, coordination of body parts was analyzed qualitatively for each day. The results showed that the infant's reaching changed from having two functions (both touching the object and adjusting the supporting surface) to having only the one function of touching the object. It appeared that an increase in flexibility of coordination of body parts was behind this change. In addition, this study showed that by creating and utilizing instability and in uplifting the upper body and extending the arms, infants may achieve new postural dynamics leading to crawling.

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Developmental niche theory (Super & Harkness, 1986) posits that children actively interact with their surroundings rather than being influenced passively by a fixed environment. Based on this theory, the present study observed the dynamic interplay between children and their environment during the transition from preschool to elementary school. To relate the niche to school culture, niche theory was redefined using the term "school developmental niche" and adjustment processes between children and the environment were studied at a preschool and elementary school. Data were based on weekly observations of children over a nine month period before and after the April transition to elementary school along with interviews with their preschool teachers, first grade classroom teacher, and mothers. The results showed that children interacted differently according to their specific niche, and differed in their level of active participation in the interplay. This suggests that ecological aspects of the school developmental niche constitute a challenge to a smooth transition to elementary school.

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The present study examined the development of the ability of 3- to 6-year-old children (N=105) to give information appropriately to others. In a game, each participant was allowed to see where the target was hidden in one of the two cups, while the child's partner (a collaborator or competitor) was not. In the collaborative situation, the collaborator asked the child if he/she knew the location of the target object. If a child gave information to the collaborator, the child was given the target. In the competitive situation, the competitor asked children the question in the same way as in the collaborative situation. But if children gave information to the competitor, the target was taken by the competitor. The results showed that most 3 yearolds pointed to the location of the target immediately in both situations. However, 5-6 year-olds gave information appropriately to the collaborator and not to the competitor partner. There was a significant correlation between performance in the hiding game, and that in the inhibitory task which required a novel response in the face of a conflicting prepotent response. These findings suggested that inhibitory control may be an important contributor to children's understanding of the other's mental state.

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The present study examined the ability of young children to monitor two external sources. In Experiment 1, 5- and 6-yearolds and adults listened to a list of words spoken by two sources, a male and a female. Some words in the list were common to both sources, whereas others were unique to one source. After approximately two minutes participants were given a recognition test, and a source monitoring test in which they were asked to identify the source of each word as one of four alternatives (male voice only, female voice only, both voices, neither voice). Children made more source monitoring errors than did adults, arid they had the greatest difficulty identifying sources of the words which had been given by both sources. In Experiment 2, the materials and procedures were identical to those in Experiment, except that the words were presented both as visual images (picture cards) and as sounds (a female voice). The results of Experiment 2 were almost the same as in Experiment 1.

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The present study investigated the relations between students' trust for teachers and school adjustment. A sample of 457 junior high school students completed questionnaires, and the results were as following. (1) Students' trust for teachers influenced not only the student-teacher relationship but also other aspects of school adjustment including "willingness to learning," "future direction," "attitude toward school rules," and "attitude toward school activities." (2) At each grade level, students' trust for teachers had a different influence on adjustment to school life. In seventh grade, a "sense of security" toward teachers consistently influenced how they adapted to school. (3) In the eighth and ninth grades, in addition to "sense of security," "distrust" and "evaluation of role accomplishment" also had an influence. (4) At all three grade levels, in relation to students' trust for teachers, "sense of security" had the greatest influence on school adjustment. (5) School adjustment depended on the pattern of students' trust for teachers, e.g., a "trust type," "role dominance type," "distrust dominance type," and "ambivalent type."

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