Background: There are still a lot of unknown aspects about the childhood development of sociability which are based on neuroscientific basis. Purpose of the Japan Children’s Study (JCS) was to verify the normal process of child development of sociability; the trajectory and factors related development of sociability, and to collect findings and integrate the knowledge to make the plan of long-term and large scale cohort study.
Methods: A child cohort study underway in Japan since 2005. There are the cohort study including a infant cohort study at age of 4 months to 30 months and a preschool cohort study at age of 5 years old to 8 years old. Questionnaires, direct observation of children and cognitive testing were performed.
Results: In infant cohort study, 465 infants were recruited at 4 months and 367 children were followed up to 30 months, follow up rate was 78.9% and in the preschool cohort study, total 192 children (112 at 2005 and 80 at 2007) at age of 5 years old and 169 followed up to 6 years (follow up rate was 88.0%), and 79 children were followed up to 8 years old (follow up rate was 70.5%) old. Several new measurements to evaluate child sociability were developed. Some factors related to development of child sociability were found for example the ‘praise’ was related to child sociability in cohort study based on neuroscience findings.
Conclusions: Though the trajectory of child sociability development were not clarified, some significant factors related to development of sociability, and the basic findings to conduct a long-term and large scale cohort study were provided.

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Background: The Tottori study group, part of the JCS, presides over a community-based cohort study started when subjects—children living in Tottori City—were 5 years old. The social aspects of conducting a cohort study should also be made public, as this information is crucial for conducting community-based cohort studies.
Methods: Documents pertaining to social aspects implemented by the Tottori study group between 2004 and 2008 were arranged chronologically. Information which is crucial for conducting community-based cohort studies were extracted and classified into several categories.
Results: Five categories were extracted from the documents: research staff, supporting committee, recruitment, maintenance of motivation and disclosure. Implementation of the social aspects described in maintenance of motivation resulted in fewer subjects dropping out of the study and a re-recruitment rate of approximately 90%.
Conclusions: The following factors are essential for a successful developmental cohort study of children: 1) A birth cohort study should be planned in hospitals with medical staff such as obstetricians and pediatricians; 2) An interdisciplinary group composed of medical or psychological clinicians and researchers with abundant experience in epidemiological study should be included; 3) If possible, an expert or widely known individual in the study’s target field should be included as a member of the study staff; 4) For long cohort studies, a researcher with expertise in school education should be included; 5) A support committee should be organized as an external part of the study team.

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Background: We investigated the feasibility and validity of and systematized the methods used to enroll and retain participants requiring long-term interdisciplinary collaborations. We carried out this study in the Sukusuku cohort, Mie (SCM), as one of the regional research site of Japan Children’s Study (JCS).
Methods: A total of 467 families who were screened between December 1, 2004 and December 31, 2005, in the Mie-chuo Medical Center and 2 other hospitals; these families were deemed eligible for the study. Of these, a total of 185 families (39.6%) participated in the 4-month observation. Of these families, 5 dropped out at month 9 of the observation; 9, at month 18; 17, at month 30; and 5, at month 42. The retention rates at 9, 18, 30, and 42 months of observation were 97.3%, 92.4%, 83.2%, and 80.5%, respectively. Reinstatement to a previous job was the most common reason for dropouts.
Results: We observed that informative consultation notes during observation were beneficial for the retention of participants, and these notes also helped in improving communication between the study subjects and the evaluators during subsequent visits.
Conclusions: In this study, we did not perform the standard checks for child development alone but also investigated the motivating influence of research partnerships with participants. Further, these visits help maintain the motivation levels of the participants and encourage them to contribute for social causes. The results present integration models that can be applied in future relevant longitudinal cohort studies in Japan.

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Background: We carried out Sukusuku cohort, Mie (SCM), a long term cohort study of child development and investigated the feasibility and validity of this study. Then we focused on the characteristics of the enrolled families and verified the representativeness of the participants in SCM.
Methods: The characteristics of 185 families recruited from 3 hospitals were analyzed, and we verified the representativeness of these subjects. We also analyzed the factors that may influence the mental health of the mothers who are raising children.
Results: There were no significant differences between the subjects from the 3 hospitals in terms of the age distribution, academic background, occupation, and annual income of the participating families. At 42 months, the average developmental quotients for postural and motor, cognitive and adaptive, and speech and social development in the 140 infants were 98.6, 100.6, and 99.9, respectively. The overall developmental quotient for infants was 100.3 ± 13.2; this score was within the standard range (55–132). The path-analysis model revealed that family function was an important factor influencing the mental health of mothers.
Conclusions: The participant characteristics were thought to be generally representative, and we showed the validity and representativeness of the participants in this cohort study. The mental health analysis of mothers suggested that relieving mothers from child-rearing stress and maintaining family function were important for the maintenance and improvement of maternal mental health.

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Background: The purpose of this paper is to describe the features of the Interaction Rating Scale (IRS) as an evidence-based practical index of children’s social skills and parenting.
Methods: The participants in our study, which was conducted as part of a Japan Science and Technology Agency (JST) project, were 370 dyads of children (aged 18, 30, and 42 month) and 81 dyads of 7-year-old children with their caregivers. The participants completed the five minute interaction session and were observed using the IRS.
Results: The results indicated that the IRS can measure children’s social skill development and parenting with high validity. Along with the discriminate validity for pervasive development disorder (PDD), attention-deficit/hyperactivity disorder (ADHD), abuse and maltreatment, a high correlation with the SDQ (Strength and Difficulties Questionnaire), and high reliability, the IRS is effective in describing features of social skill development.
Conclusions: The IRS provides further evidence of the fact that in order to study children’s social skill development, it is important to evaluate various features of the caregiver-child interaction as a predictor of social skills.

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Background: It is clear that early social interaction follows from mother-infant interaction after pregnancy. Many researchers have illuminated this interaction in the first years of life. Most common mother-infant interaction is the attachment behavior of an infant. The Japan Children’s Study (JCS) development psychology group hypothesis is that the early mother-infant interaction will predict later social behaviors. But the method applied to evaluate this interaction mainly comes from the evaluation of the whole observation situation and is dependent upon the coder. We applied a new observational method that checked the on/off status of behavior and recorded sequentially.
Methods: Using a semi-structured observation setting as our method, we analyzed the developmental change of mother-infant interaction within a toy situation.
Results: The result indicated that mother-infant interaction with a toy altered at around 9-months and is salient to the usual developmental change of joint attention. Additionally cluster analysis suggested that the developmental pattern is divided into two clusters. This is the first report on a developmental pattern of joint attention.
Conclusions: These results indicated that the developmental trend of gaze direction and vocalization is one candidate of measure for evaluating the mother infant social interaction from the point of joint attention.

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Background: This study investigated developmental change and stability in infant responses to the still-face (SF) situation, as well as predictive validity at age 18 months, focusing on autonomy and responsiveness.
Methods: A total of 231 children (117 boys and 114 girls) and their Japanese mothers were observed in a face-to-face SF situation at two infant ages (4 and 9 months), as well as a caregiver-child teaching interaction at age 18 months. Each infant’s facial expression, gaze direction, and vocalization were coded according to the SF paradigm, including the Natural Interaction (NI) and SF phases. Each child’s Autonomy and Responsiveness to the Caregiver at age 18 months were both evaluated by means of the Interaction Rating Scale.
Results: The results indicated that negative facial expression and vocalization in the SF phases at age 9 months predicted the Autonomy rating at age 18 months, while positive facial expression and gaze toward the caregiver in the NI at age 9 months predicted the Responsiveness to Caregiver rating at age 18 months.
Conclusions: The results are discussed in the context of developmental continuity and change in the children’s social cognition and voluntary movements.

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Background: Praise from caregivers has been shown as an important influence on the development of social competence in early adolescence. However, the effects of praise in younger children have not been investigated. We examined how the trajectory of children’s social competence from 18 months to 30 months of age was related to their caregiver’s attitude towards the importance of praise at times when their child was 4 months and 9 months old.
Methods: We studied 155 mother-child dyads, whose interactions during play were observed both when the child was 18 months and 30 months old, which was conducted as part of a Japan Science and Technology Agency (JST) project. The child’s social competence was assessed using the Interaction Rating Scale (IRS). Demographic data was obtained when the child was 4 months old, and the caregiver’s attitude towards the importance of praise when the child was both 4 months and 9 months old. A logistic regression analysis controlling for the effects of demographic variables was performed.
Results: We found that children who had received continuous praise from their mother when they were 4–9 months of age had a decreased risk of low social competence at 18–30 months of age.
Conclusions: A mother’s attitude towards the importance of praise at early stages of her child’s development has an important influence on the later trajectory of social competence.

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Background: The purpose of this study was to examine the relations between children’s social competence and initial index of theory of mind at 30 months of age.
Methods: The participants of the study were 322 toddlers and parents/caregivers who were registered with the Japan Science and Technology Agency (JST) project. They completed a five-minute interaction session, which was coded using the Interaction Rating Scale (IRS) as an evidence-based practical index of children’s social competence. In addition, the children were asked to complete a diverse-desire task as a ToM (theory of mind) index.
Results: The results showed that the ToM index was related to the total score and subscales of the IRS, such as Empathy and Emotional regulation.
Conclusions: These findings show that the IRS score was related to ToM task performance at 30 months of age.

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Background: Little is known about how contributing factors of development change during early childhood in Japan. The aim of this study was to investigate the factors that contributed to the developmental attainment of children between 9 and 18 months of age using prospective longitudinal data from a developmental cohort study.
Methods: We used data from observations at 3 time points (at infant age of 4, 9 and 18 months) in the Japan Children’s Study. Mothers were administered questionnaires that requested information about their child’s perinatal outcomes, temperament, family structure, family income, parental education, parenting stress, and child-rearing environment at home. At 9 and 18 months, mothers completed the Kinder Infant Development Scale to evaluate their child’s development.
Results: A total of 284 children were available for analysis. Female children and children having siblings had higher probability of attaining developmental norms at 18 months than male and only children. Birth weight, gestational age, and temperament were associated with development at 9 months, but the effects of gestational age and temperament on development disappeared at 18 months. Stimulation from the mother at 9 months was not only related to development at that age but also promoted development at 18 months.
Conclusions: Our findings suggest that the role of family environmental factors such as early mother’s stimulation and sibling’s existence in development during early childhood might become more important as the child gets older.

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Background: Many studies have suggested that the daily emotional interactions between a child and his/her caregiver play a significant role in his/her development. The purpose of this study was to determine whether the trajectory patterns of parenting patterns of caregivers raising toddlers affect the social competence of the toddlers.
Methods: The study participants were 246 dyads of 18-month-old children (baseline) and their caregivers, which was conducted as part of a Japan Science and Technology Agency (JST) project. We used the Interaction Rating Scale (IRS) to evaluate the children’s social competence. We assessed the child rearing environments by analyzing the caregivers’ responses to the Index of Child Care Environment (ICCE).
Results: Multiple logistic regression analysis showed that the children’s total score on the IRS was significantly related to how frequently they sang songs together with their caregivers. Their score was also significantly related to how closely their caregiver worked with his/her partner in raising the child. These relationships did not change according to demographic information.
Conclusions: The results confirm previous findings on the relationship between parenting patterns and children’s social competence. In particular, the study shows that varied and continual parenting significantly affects a child’s social competence.

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Background: The present study examines gender differences in the correlations between intelligence and developmental problems as well as social competence in first graders.
Methods: Ninety parent-child dyads participated in this study. The children comprised 7-year-olds recruited from the first grade of an elementary school. All the children were administered the Wechsler Intelligence Scale for Children–Third Edition (WISC-III), Parent-child Interaction Rating Scale (IRS), and the parent report version of Strength and Difficulties Questionnaire (SDQ).
Results: The findings clarified that the processing speed of boys significantly correlated with their peer relationship. On the other hand, the emotional symptoms exhibited by girls had a more common association with their intellectual abilities. The correlations between parenting and intellectual abilities differed in boys and girls.
Conclusions: Children’s gender should be taken into account when assessing the diversity in their intellectual abilities and developmental problems. Moreover, parenting also influences the development of children in various ways.

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Background: It is known that sleep problems impact children’s health, learning, and school performance. The purpose of this paper is to examine the association between sleeping habits and social competence development.
Methods: Three hundred and nine caregiver-child dyads participated in this study, which was conducted as part of a Japan Science and Technology Agency (JST) project. The caregivers answered some questionnaires about sleeping habits when the child was 9 months and 18 months old. Caregiver-child interaction was observed when the child was 30 months old, and the features of the interaction were examined using the Interaction Rating Scale (IRS) as a measure of social competence.
Results: The caregivers’ attitude toward sleeping in the 9-month period was found to be significantly correlated with the children’s social competence at 30 months. Moreover the caregivers’ attitude toward sleeping in the 9-month period significantly correlated with the children’s sleeping habits at 9 and 18 months.
Conclusions: These findings show that the caregivers’ attitude toward sleeping is an important factor influencing the development of children’s social competence.

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Background: A child’s sleep pattern is important in defining his or her mental and physical well-being. Although we have reported previously on the utility of collecting 2 weeks of daily sleep logs, this type of record keeping is often onerous for the parents. Therefore, we established a new questionnaire, called the Japan Children’s Study Sleep Questionnaire (JCSSQ), which is used to collect sleep pattern data over 4 weeks, including weekdays, Saturdays, Sundays, and holidays.
Methods: Two parent-administered sleep assessment tools, the JCSSQ and a daily sleep log, were used to examine the sleeping patterns of 105 school children (58 boys and 47 girls; age range, 6–12 years) in Fukuoka, Japan. Parents were requested to record sleep logs for 14 days after the JCSSQ. Sleep/wake status was recorded on the sleep log, from which data on the parameters of “sleep onset time”, “waking time”, “sleep period”, and “number of nights waking” were extracted.
Results: There were no significant differences between the JCSSQ and the logs for waking time data collected on weekdays, Saturdays, and Sundays. However, there was a significant difference (P = 0.03) between the JCSSQ and the sleep logs with respect to the sleep onset time data collected on Saturdays.
Conclusions: The JCSSQ was easy to fill out, and the data collected using the JCSSQ on weekdays were both valid and generally consistent with those collected using sleep logs. However, for sampling on Saturdays and Sundays, the JCSSQ data did not correlate with the sleep log data.

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Background: Previous research has suggested that television (TV) viewing may be associated with increased behavioral and emotional problems in children. However, there are few prospective studies targeted for its association with outcomes of children under 3 years old. The purpose of this study was to exam the association between children’s early TV exposure at ages 18 and 30 months and the behavioral and emotional outcomes at age 30 months.
Methods: We analyzed data collected prospectively in the Japan Children’s Study. TV exposure was assessed by mothers’ report at infant ages of 18 and 30 months. The outcomes were assessed using the Strengths and Difficulties Questionnaire (SDQ). Analysis of Covariance was used to estimate the effect of TV exposure on behavioral and emotional outcomes.
Results: The percentage of children who watched TV 4 hours or more per day was 29.4% at age 18 months, 24.5% at age 30 months, and 21% at both ages. Hyperactivity–inattention at age 30 months was positively associated with TV exposure at age 18 months, whereas prosocial behavior was negatively associated with hours of exposure even after adjustment. However, there were no significant differences in SDQ subscales according to daily hours of TV viewing at age 30 months.
Conclusions: Daily TV exposure at age 18 months was associated with hyperactivity–inattention and prosocial behavior at age 30 months. However, the directly casual relation was not proved in the present study. Additional research considering the TV program content and exposure timing are needed to investigate the causal relation between TV viewing and behavioral outcome.

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Background: To evaluate children’s sociability through their behavior, we compared the motion features of children with high functioning pervasive developmental disorders (HFPDD) and typical development (TD) during a game. We selected ‘Jenga’ as the game because this is an interactive game played by two people.
Methods: We observed the behavior of 7 children with HFPDD and 10 children with TD. An optical motion capture system was used to follow the movement of 3-dimensional position markers attached to caps worn by the players.
Results: The range of head motion of the children with HFPDD was narrower than that of the control group, especially in the X-axis direction (perpendicular to the line connecting the two players). In each game, we calculated the range of motion in the X-axis of each child and divided that figure by the matched adult player’s range. The average ratios of children with HFPDD and TD were 0.64 and 0.89 (number of games are 61 and 18), and the difference of these two ratios is significant (P < 0.001).
Conclusions: This ratio has sensitivity to identify HFPDD children and could be useful in their child care.

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Background: The increasing use of magnetic resonance imaging (MRI) in brain researches has led to growing concern over incidental findings (IFs). To establish a practical management protocol for IFs, it is useful to know the actual prevalence and problems of IF management. In the present study, we report the prevalence proportion and some handling problems of IFs in healthy Japanese children, and suggest a management protocol from ethical and practical standpoints.
Methods: Between 2006 and 2008, 120 healthy children aged 5–8 years participated in a structural MRI study conducted in a pediatric cohort in Japan. All MRI images were reviewed by a pediatric neurologist, and detected IFs were classified into 4 categories.
Results: IFs of all categories were detected in 40 of the 110 participants (36.4%) for whom T2-weighted or 3D-T1-weighted images were available. Findings of sinusitis and/or otitis media were most frequent (26.4%). Excluding these findings, the prevalence of IFs was still 10.9% (12 findings): 9 findings were categorized as “no referral” (8.2%), 2 as “routine referral” (1.8%), 1 as “urgent referral” (0.9%), and 0 as “immediate referral” (0.0%). In “routine referral” category, only one participant was referred for further examinations.
Conclusions: Although the prevalence of IFs was high, the proportion of those requiring further examination was low. This result revealed a fairly high false-positive rate and suggested that evaluating equivocal findings was the most difficult part of IF management. A management protocol needs to include a process to properly assess the clinical importance of findings.

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