Page 126 - Like me, or else... - Michelle Achterberg

Chapter 5
Parenting intervention
Families were contacted 1.5 year after W1 to inform them on a parenting support program for parents of twins (VIPP-Twins (Euser et al., 2016)). We then explained that we were unable to personally visit all families within the L-CID to offer the training. Therefore, families would be randomly assigned to either receiving the training in person, through six home visits (see Juffer and Bakermans-Kranenburg (2018)), or to alternatively discuss the development of your twin through six phone meetings (dummy intervention - control group). Detailed sample selection is described in the supplementary materials. The VIPP-Twins group consisted of n=164 children, of which 133 had sufficient quality MRI data (Figure S1). The control group consisted of n=244 children, of which n=186 had sufficient quality MRI data (Figure S1). Twenty-seven families (n=54 children) did not comply with random assignment to one of the conditions. These families received the (non- randomly assigned) dummy intervention in order to keep this group comparable to the control group for future analyses within the longitudinal L-CID study. Given that the participants in the non-randomly assigned control group could not be included in the analyses, these participants’ MRI data were used as a reference group, and used to create task-relevant independent regions of interest (ROI) (see section 2.4.4).
Social Network Aggression Task
The Social Network Aggression Task (SNAT) as described in Achterberg et al. (2016b; 2017; 2018b) was used to measure aggression after social feedback. Participants viewed pictures of peers that gave positive, neutral or negative feedback to the participant’s profile. Next, participants could blast a loud noise towards the peer as an index of aggression. To keep task demands as similar as possible between the conditions, participants were instructed to always press the button. The longer they pressed the button the more intense the noise would be, which was visually represented by a volume bar. Participants received instructions on how to perform the SNAT and the children were exposed to the noise blast during a practice session. Thereafter, participants practiced six trials of the task. The time line of a SNAT trial was as follows: start screen (500 ms), social feedback (2500 ms), fixation screen (3000-5000 ms), noise screen (5000 ms), intra-trial interval fixation screen (0-11550 ms), see Figure 1a. The optimal jitter timing and order of events were calculated with Optseq 2 (Dale, 1999). The SNAT consisted of 60 trials, three runs of 20 trials for each feedback condition (positive, neutral, negative). Intra class coefficient (ICC) analyses (modeled with a two-way mixed model using the consistency definition) showed poor (ICC<0.40, (Cicchetti, 1994)) consistency in noise blast duration after positive (ICC=0.32 [95%CI= 0.24-0.41]), neutral (ICC=0.26 [ 95%CI=0.17-0.35]) and negative feedback (ICC=0.17 [95%CI=0.08 - 0.26)] between W1 and W2.
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