Short-term direct reciprocity of prosocial behaviors in Japanese preschool children.

Direct reciprocity plays an essential role in forming cooperative relationships. Direct reciprocity requires individuals to keep track of past interactions and condition their behavior on the previous behavior of their partners. In controlled experimental situations, it is known that children establish direct reciprocity according to the partner's behavior, but this has not been verified in real life. This study aims to identify the establishment of short-term direct reciprocity in response to peers' behaviors among Japanese preschoolers aged 5 and 6. It employs naturalistic observation at a nursery school. In addition, the psychological process for direct reciprocity was examined. The findings demonstrated that after receiving prosocial behavior, the recipient child returned the prosocial behavior more frequently within 7 minutes, compared with control situations; this suggests that 5-to 6-year-olds formed direct reciprocity in the short term when interacting with their peers. Additionally, recipient children tended to display affiliative behavior after receiving prosocial behavior. Positive emotions toward initiating children may have been caused by receiving prosocial behavior, and this psychological change modified short-term direct reciprocity.

Physical fitness of non-disabled school-aged children born with extremely low birth weights.

BACKGROUND: The assessment of long-term outcomes in survivors born with extremely low birth weights (ELBWs) has become increasingly important. However, little has been reported on the physical fitness of non-disabled school-aged children born with ELBWs. AIMS: To assess the physical fitness of non-disabled school-aged children born with ELBWs. STUDY DESIGN: Retrospective cohort study. SUBJECTS: We analyzed 169 ELBW infants without cerebral palsy or intellectual disability (based on the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) Full Scale intelligence quotient (IQ) test < 70). OUTCOME MEASURES: Physical fitness was assessed using the grip strength, sit-up repetitions, sit & reach, side steps, standing long jump, and softball throw tests. T-scores were calculated using national survey data. RESULTS: The T-scores for the grip strength, sit-up repetitions, sit & reach, side steps, standing long jump, softball throw tests, and the overall T-score were 43.7 ±â€¯7.5, 44.2 ±â€¯10.5, 46.0 ±â€¯9.7, 40.9 ±â€¯8.0, 40.0 ±â€¯9.8, 42.4 ±â€¯8.1, and 42.9 ±â€¯5.5, respectively. After adjusting for other age-related factors, the height (SD score), WISC-III Performance IQ score, and percent predicted forced vital capacity (FVC) independently predicted the overall T-scores. Their standardized partial regression coefficients (ß) were 0.334 (p = 0.009), 0.190 (p = 0.022), and 0.187 (p = 0.032), respectively. CONCLUSIONS: Our cohort's physical fitness at approximately 8 years of age was significantly impaired compared to average Japanese children of the same age. Height, FVC, and Performance IQ independently predicted physical fitness, with height being the strongest predictor.

Perinatal factors associated with long-term respiratory sequelae in extremely low birthweight infants.

OBJECTIVE: To assess lung function at 8 years old in extremely low birthweight (ELBW) survivors and to identify perinatal determinants associated with impaired lung function. DESIGN: Retrospective cohort study. SETTING: Level III neonatal intensive care unit. PATIENTS: ELBW survivors born in 1990-2004 with available spirometry at 8 years old were studied. Children were excluded if they had a Wechsler Intelligence Scale for Children Third Edition full IQ <70. MAIN OUTCOME MEASURES: Multivariate logistic regression analysis was used to identify perinatal determinants associated with airway obstruction (forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio <80%) at school age and the predictive power of potential determinants. Potential risk factors and predictors assessed in this study were gestational age, birth weight, small for gestational age, sex, chorioamnionitis, premature rupture of membranes, antenatal steroids, surfactant administration, respiratory distress syndrome, postnatal steroids, severe bronchopulmonary dysplasia and bubbly/cystic appearances of the lungs by X-ray during the neonatal period. RESULTS: Of 656 ELBW survivors, 301 (45.9%) had attended a school-age follow-up at 8 years old. A total of 201 eligible children completed the lung function test. Bubbly/cystic appearance of the lungs (OR 4.84, 95% CI 1.26 to 18.70) was associated with a low FEV1/FVC ratio. Children with bubbly/cystic appearance had characteristics of immaturity and intrauterine inflammation. CONCLUSIONS: Within a cohort of ELBW infants, a bubbly/cystic appearance of the lungs in the neonatal period was the strongest determinant of a low FEV1/FVC ratio at school age.

Long-term alpha-tocopherol supplements may improve mental development in extremely low birthweight infants.

AIM: Methods to improve the mental development of extremely low birthweight (ELBW) children are currently lacking. We assessed the effects of long-term supplementation of alpha-tocopherol on the neurological development of 259 school-aged ELBW children. METHODS: Extremely low birthweight participants were divided into three groups: group A with no alpha-tocopherol supplementation (n = 121); group B with the supplementation for <6 months (n = 104) and group C with the supplementation for more than 6 months (n = 34). We analysed the participants' data at birth and between the ages of one-and-a-half to 8 years and evaluated potential factors associated with intellectual disabilities. RESULTS: Children from group C had the best outcome. The groups' mean gestational weeks and mean ventilator days were as follows: 27.5 weeks, 16.1 days (group A); 25.7 weeks, 41.7 days (group B); and 25.1 weeks, 75.5 days (group C). Multivariate regression analysis revealed that the odds ratios for impaired mental development at 8 years were 1.5 in group B and 0.19 (p = 0.017) in group C, compared with 1.0 in group A. The association between the duration of alpha-tocopherol administration and performance intelligence quotient (IQ) was dose dependent (p = 0.03). CONCLUSION: Long-term supplementation of alpha-tocopherol appeared to improve mental development, in particular, performance IQ, in school-aged ELBW children.

Preschool children's behavioral tendency toward social indirect reciprocity.

Social indirect reciprocity seems to be crucial in enabling large-scale cooperative networks among genetically unrelated individuals in humans. However, there are relatively few studies on social indirect reciprocity in children compared to adults. Investigating whether young children have a behavioral tendency toward social indirect reciprocity will help us understand how and when the fundamental ability to form cooperative relationships among adults is acquired. Using naturalistic observation at a nursery school, this study examined whether 5- to 6-year-olds show a behavioral tendency to engage in social indirect reciprocity in response to their peers' prosocial behavior toward a third party. The results revealed that bystander children tended to display prosocial behavior toward their peers more frequently after observing these peers' prosocial behavior toward third-party peers, compared with control situations; this suggests that 5- to 6-year-olds may have an essential behavioral tendency to establish social indirect reciprocity when interacting with peers in their daily lives. In addition, bystanders tended to display affiliative behavior after observing focal children's prosocial behavior. In other words, observing peers' prosocial behavior toward third-party peers evoked bystanders' positive emotions toward the helpers. Considering both the present results and previous findings, we speculate that in preschoolers, such positive emotions might mediate the increase in the bystander's prosocial behavior toward the helper. In addition, an intuitional emotional process plays an important role in the preschooler's behavioral tendency toward social indirect reciprocity in natural interactions with peers.