BackgroundIntervention programs with the aim of enhancing parenting quality have been found to be differentially effective in decreasing negative child outcomes such as externalizing behavioral problems, resulting in modest overall effect sizes. Here we present the protocol for a randomized controlled trial to examine the efficacy of the Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline for Twin Families (VIPP-Twins) on parenting quality and children’s behavioral control and social competence. In addition, we aim to test the differential susceptibility theory; we examine differential efficacy of the intervention based on genetic make-up or temperament for both parents and children. Lastly, we explore neurobiological mechanisms underlying intervention effects on children’s developmental outcomes.Methods/designThe original VIPP-SD was adapted for use in families with twins. The VIPP-Twins consists of five biweekly sessions in which the families are visited at home, parent-child interactions are videotaped and parents receive positive feedback on selected video fragments. Families (N = 225) with a same sex twin (mean age = 3.6 years) were recruited to participate in the study. The study consists of four assessments. After two baseline assessments in year 1 and year 2, a random 40 % of the sample will receive the VIPP-Twins program. The first post-test assessment will be carried out one month after the intervention and there will be a long term follow-up assessment two years after the intervention. Measures include observational assessments of parenting and children’s social competence and behavioral control, and neurobiological assessments (i.e., hormonal functioning and neural (re-)activity).DiscussionResults of the study will provide insights in the efficacy of the VIPP-Twins and reveal moderators and mediators of program efficacy. Overall the randomized controlled trial is an experimental test of the differential susceptibility theory.Trial registrationDutch Trial Register: NTR5312; Date registered: July 20, 2015.Electronic supplementary materialThe online version of this article (doi:10.1186/s40359-016-0139-y) contains supplementary material, which is available to authorized users.

To thrive as an individual and within society, children need to develop the ability to control their behavior. Using a twin design, we estimated the relative influence of genetic, shared, and unique environmental factors on hot and cool effortful control (EC). Furthermore, we investigated whether parental sensitivity in a play, task, or discipline context when the children were on average 3.78 years old, was differentially related to children's hot and cool EC 1 year later (M age 4.77 years). We included 476 children from 238 twin pairs (48% boys, 58% monozygotic) and their primary parent. Hot EC (delay of gratification) was measured with the marshmallow test and cool EC (response inhibition) was measured with a stop-signal task. The behavioral genetics analyses showed that individual differences in hot and cool EC were mostly explained by unique environmental factors, whereas their association was mostly explained by shared environmental factors. Controlling for sensitivity in the other contexts, task sensitivity contributed to the prediction of cool EC, and sensitive discipline contributed to both cool and hot EC. Play sensitivity did not contribute to the prediction of hot or cool EC over and above parental sensitivity in the other contexts. Our study contributes to a better understanding of the unique and shared antecedents of hot and cool EC, suggesting parental sensitive discipline as a focus for preventive interventions targeting both hot and cool EC.

Temperament has been suggested to be influenced by genetic and environmental factors. The current study examined genetic shared environmental and unique environmental factors accounting for variation in Fear, Effortful Control (EC), and Frontal Asymmetry (FA) in 4-to 6-year-old children using bivariate behavioral genetic modeling. We included a total of 214 same-sex twin pairs: 127 monozygotic (MZ) and 87 dizygotic (DZ) pairs. FA was measured during a rest electroencephalogram (EEG) recording, and Fear and EC were measured using parent report. Results show that differences between twins were best explained by genetic factors (about a quarter of the variance) and unique environmental factors (about three quarters of the variance). However, the cross-trait, within-twin correlations were not significant, implying no overlapping genetic or environmental factors on Fear and EC or on Fear and FA. Future research should try to elucidate the large role of unique environmental factors in explaining variance in these temperament-related traits.

Early in their lives young children are confronted with social judgments by peers. Previous studies have shown that in adults negative social judgments are associated with more aggressive behavior. However, little is known about the relation between social judgments and aggressive behavior, or the underlying neurocognitive mechanisms, in early childhood. We developed the Social Network Aggression Task - Early Childhood (SNAT-EC) to examine the mediating role of frontal EEG asymmetry in the relation between social judgment and aggressive behavior in 4-6 year old children. To replicate our findings, we included three samples: a pilot sample, test sample 1 and test sample 2 (total N = 78). In the SNAT-EC, children receive positive, negative and neutral social judgments about their chosen cuddly animal by same-aged unfamiliar peers. EEG was acquired to measure frontal asymmetry during the processing of social judgments. Aggressive behavior was measured as the duration of a button press with which children could destroy balloons of the judging peer, thus reducing the number of remaining balloons for that peer. We used a within-subject mediation model to test whether frontal asymmetry mediated the effect of social judgment (negative vs. positive) on aggressive behavior. Results show that the SNAT-EC robustly elicits more aggressive behavior in response to negative social judgments about the cuddly animal compared to positive judgments. Meta-analysis revealed a large combined effect size (r = .42) for the relation between negative (vs. positive) social judgments and aggressive behavior. However, frontal asymmetry in response to the social judgments did not mediate the relation between social judgment and aggressive behavior. Future studies should search for other neural mediators to bridge the brain-behavior gap between social judgments and aggressive behavior, in particular in early childhood.