Main objective 1:
Study the impact of elementary school social experiences on DNA methylation and cognitive development above and beyond possible genetic effects in monozygotic twins concordant/discordant on bully-victimization.
Data from 196 monozygotic twin pairs are currently being collected. Data are collected at two time-points, when the twins are on average seven years old, and one year later, when the twins are on average 8 years old. Twins, classmates, and teachers are informants.
Main objective 2:
Study the cross-time influence of multiple adverse and protective social experiences with peers and teachers to test for possible cascading, accentuation and buffering between different social experiences, and test for sex-differences in these influences in a longitudinal observational study of children followed across elementary school.
Data among 1000+ children attending mainstream elementary schools have been collected. Children have been assessed annually across the elementary school years (age 5 - 12 years). Teacher, peer, and self-report data on children's social relations and social experiences with teachers and classroom peers, and on children's psychopathology have been collected. Test scores of children's social decision making, working-memory, risk-taking, and behavioral inhibition were obtained annually. Three waves of DNA have also been collected, and DNA epigenetic analyses (EPIC array) are currently conducted.
Main objective 3:
Study hypothesized stress- and self-regulatory variables that mediate the effects of altered DNA methylation and altered neurocognitive functions on aggressive responses. Children discordant on their social experiences in school will be tested in two lab-experimental studies.
In study 1, 70 children (50% rejected) were tested in an fMRI study. In the fMRI experiement, children completed a dictator game, followed by a social exclusion task (Cyberball), followed by a second dictator game.
55 children (50% rejected) were invited to participate in the stress-lab study. Children's heart rate and cortisol concentrations were administered during the lab-assessment. Children first completed the BART-task, followed by a social exclusion experience. Children then completed the social decisions task (Hungry Donkey task).