| Prosocial behaviors refer to the voluntary behaviors that individuals act to benefit others.The individual differences in prosocial development partially rooted in genetic variation and correlate with the differences in children's neurophysiological function.Besides,children's prosocial development is under the effect of the acquired growth environment,especially the family environment.Different parenting practices,as the core process of family socialization,could directly contribute to children's prosocial development.According to the Hay and Cook's theory,the prosocial development trend of elementary school children remains stable,and different biological dispositions and external environment work together to affect children's prosocial development and increase the developmental heterogeneity.Thus,studying the prosocial development in elementary school children should both consider the effect of children's neurobiological function as well as the parenting practices.Over the past decades,researchers had put forward the diathesis-stress model,sensory processing sensitivity mode,differential susceptibility model,biological sensitivity to context model and vantage sensitivity model in succession based on the perspectives of psychopathology,evolutionary psychology and development psychology.All the theoretical models consistently believed that children with different internal dispositions also had different environmental sensitivities,which could heighten or alleviate the influence of different environment on children's mental and behavior development,and finally interacted with different environment to form the individual differences in children's prosocial development.Based on the biological-environment interaction theoretical models,this study investigated the prosocial development trend in children,the neurobiological function of children's prosocial development(including the genetic basis and the vagal tone),the effect of different parenting practices on children's prosocial development,and more importantly,examining the interaction effects of different neurobiological function and parenting practices on children's prosocial development through five parts.In the first part,the study examined the general developmental trajectories of children's prosocial behaviors from the 1st grade to the 3rd grade in elementary school.208 primary school students(98 girls,47.1%)participated in the present longitudinal study.Parents reported children's prosocial behaviors using the prosocial scale of the Strength and Difficulties Questionnaire when children were at 1st,2nd and 3rd grades.The results supported Hay and Cook's theory,suggesting that prosocial behaviors in this period keep stable across time(b=-0.10,p=0.29,95%CI=[-0.28,0.08]),but the individual differences in children's prosocial behaviors were significant(b=1.35,p<0.001,95%CI=[7.10,7.91]).In the second part,the study examined different neuroendocrine system genes,including oxytocin receptor(OXTR)gene polymorphism and corticotropin-releasing hormone type 1 receptor(CRHR1)gene polymorphism and their associations with children's prosocial development.OXTR gene and CRHR1 gene were genotyped among 208 primary school students(the same as the first part),parents reported children's prosocial behaviors using the prosocial scale of the Strength and Difficulties Questionnaire.This study found that OXTR rs53576 could interact with CRHR1 rs110402 to predict children's prosocial development(b=1.60,p=0.02,95%CI=[0.26,2.94]).Specifically,children with rs53576 AA genotype and rs110402 CC/TC genotype behaved the highest prosocial behaviors during the three years.This finding firstly provided the empirical evidence for the "tend-and-befriend theory" from the genetic molecular level and supported the combined effect of oxytocin and corticotropinreleasing hormone on pro social behaviors,which implicated the role of oxytocin in the association between hypothalamic-pituitary-adrenal axis(HPA axis)reactivity and children' s prosocial development.In the third part,the study systematically examined the quadratic association between resting vagal tone(as indexed by resting respiratory sinus arrhythmia,RSA)and prosocial development in children.141 primary school children(76 girls,53.9%)participated in the first study.Parents reported children's prosocial behaviors using the prosocial scale of the Strength and Difficulties Questionnaire,and children's resting vagal tone was calculated by electrocardiogram(ECG)data collected during a resting period.Study 3a demonstrated the inverted U-shaped curve between resting RSA and prosocial behaviors in children(b=-0.32,p=0.01,95%CI=[-0.58,-0.07]).182 primary school children(87 girls,47.8%)participated in the second study.The study used dictator game to measure children's sharing behaviors to indicate prosocial behaviors.Parents reported children's empathy using the Griffith Empathy Measure,and the experimenter collected children's electrocardiogram(ECG)data during a resting period and calculated resting RSA.The study found the mediating effect of empathy in the quadratic association between resting RSA and prosocial behaviors(b=-0.15,p=0.01,95%CI=[-0.24,-0.05]),which contributed to understanding the psychological mechanism underlying the quadratic vagal tone-prosociality relationship.The third study examined the quadratic association between children's resting RSA at time 1 and their prosocial behaviors during time 1 to time 3.Parents reported 208 primary school children's prosocial behaviors using the prosocial scale of the Strength and Difficulties Questionnaire(the same as the part 1),and children's resting vagal tone was calculated by resting electrocardiogram(ECG)data collected at time 1.The results demonstrated the significant negative quadratic association between children's initial resting RSA and prosocial behaviors during the 1st grade to the 3rd grade(b=-0.15,p=0.01,95%CI=[-0.24,-0.05]),which suggested the stability of the quadratic vagal tone-prosociality relationship.In the fourth part,the study used the dimensional approach of parenting behaviors to examine positive parenting,parental involvement,poor monitoring and corporal punishment and children's prosocial development.Parents using prosocial scale of the Strength and Difficulties questionnaire and the Alabama parenting practices questionnaire-Chinese version to evaluate 208 primary school children's prosocial behaviors and parenting practices at 1st 2nd and 3rd grades.The results shown that children's prosocial behaviors increased with the increase of positive parenting practices(b=0,12,p=0.001,95%CI=[0.05,0.19])and parental involvement(b=0.15,p<0.001,95%CI=[0.09,0.20]),and children with more positive parenting practices(b=0.24,p<0.001,95%CI=[0.15,0.33])and parental involvement(b=0.18,p<0.001,95%CI=[0.13,0.24])would behave more prosocial behaviors during the three years.However,different negative parenting practices may have different impact on children's prosocial development.Higher poor monitoring,which reflecting lower parental behavioral control and supervision,could result in children's fewer prosocial behaviors(b=-0.13,p<0.001,95%CI=[-0.19,-0.07]);but parental corporal punishment did not have the significant impact on children's prosocial development(Levell:b=-0.04,p=0.15,95%CI=[-0.10,0.01];Level2:b=-0.16,p=0.06,95%CI=[-0.32,0.01]).The fifth part examined the interaction effects of children's neurobiological function(OXTR gene polymorphism,CRHR1 gene polymorphism and resting vagal tone)and different parenting practices on prosocial development.OXTR gene and CRHR1 gene were genotyped among 208 primary school children(the same as the part1).The experimenter collected children's resting ECG data and calculated resting RSA when children were in the 1st grade.Parents used prosocial scale of the Strength and Difficulties questionnaire and the Alabama parenting practices questionnaireChinese version to evaluate children's prosocial behaviors and parenting practices at 1st,2nd and 3rd grades.Results shown that OXTR rs53576,rs1042778,rs2254298,CRHR1 rs110402 and resting RSA could all significantly interact with parenting practices to affect children's prosocial development.Specifically,we found that children with OXTR rs53576 G allele were more susceptible for corporal punishment and behaved fewer prosocial behaviors(b=-0.25,p=0.03,95%CI=[-0.47,-0.03]),children with OXTR rs2254298 A allele were more susceptible for poor monitoring and behaved fewer prosocial behaviors(b=-0.215,p<0.001,95%CI=[-0.30,-0.13]),children with OXTR rs 1042778 GG genotype were more sensitive to positive practices and behaved more prosocial behaviors(b=0.16,p<0.001,95%CI=[0.02,0.26]),children with CRHR1 rs110402 C allele were more sensitive to positive practices(b=0.22,p<0.001,95%CI=[0.12,0.33]),poor monitoring(b=-0.23,p<0.001,95%CI=[-0.32,-0.14])and corporal punishment(b=-0.625 p=0.005,95%CI=[-1.04,-0,19])and behaved more or fewer prosocial behaviors.Meanwhile,more parental corporal punishment during the three years would reduce prosocial behaviors among children with moderate resting RSA at the 1st grade(b=-0.23,p=0.03,95%CI=[-0.43,-0.02]).Furthermore,we found that higher corporal punishment had a significant negative effect on prosocial behaviors among children with the genotype which were more sensitive to the corporal punishment on the OXTR gene and CRHR1 gene at the same time(b=-0.71,p=0.004,95%CI=[-1.19,-0.22]).Additionally,OXTR rs2254298,CRHR1rs110402 and positive parenting could interact with each other to affect children's prosocial development.Children with rs 110402 C allele could have been more sensitive to positive parenting and behaved more prosocial behaviors,but if these children also had rs2254298 A allele,which has been considered to indicate the higher negative environmental sensitivity,their high sensitivity to the positive parenting could be diminished,and thus,the children's prosocial behaviors would no longer significantly facilitated by positive parenting practices(b=0.13,p=0.24,95%CI=[-0.08,0.34]).Taken together,this study examined the prosocial developmental trajectories in elementary school children,investigated the inner biological dispositions of children's prosocial development from different levels of neurobiological function(genetic level and autonomic nervous system level),and compared the different interaction models of different neurobiological function and different parenting practices on prosocial development.The findings supported Hay and Cook's theory and emphasized the heterogeneity of prosocial development in this period.Moreover,the findings revealed that individual differences in prosocial development were under the joint effect of OXTR gene(relating to the oxytocin system functioning)and CRHR1 gene(relating to the HPA axis functioning),and closely correlate with children's resting vagal tone.In addition,individual differences in prosocial development are also affected by different parenting practices.Positive parenting and parental involvement had significant positive effect on children's prosocial development,while poor monitoring had significant negative effect on children's prosocial development.Most importantly,the individual differences in prosocial development are the results of the interplay between biological and social factors.The findings suggested that the individual differences in neuroendocrine functioning(i.e.,oxytocin system and HPA axis functioning)and autonomic nervous system functioning both laid the biological foundation for children' s environmental sensitivity differences,and oxytocin and corticotropin-releasing hormone could interact with each other to influence children's sensitivity to positive parenting and corporal punishment.Children's different environmental sensitivity could heighten or diminish the effect of different parenting practices on children's prosocial development,and consequently,combined with different parenting practices to shape children's different prosocial behaviors.The findings of this study contributed to understanding the complex mechanisms of different neurobiological function(gene polymorphisms of different neuroendocrine systems and vagal tone),parenting practices and their interactions on children's prosocial development. |
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