Page 31 - Like me, or else... - Michelle Achterberg

Social evaluation in childhood
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adults and adolescents, this study tested for the first time if the same regions are engaged in children, including not only positive and negative social feedback but also a neutral social feedback baseline (see Achterberg et al., 2016), and examined the relations with subsequent aggression.
Methods
Participants
Participants in this study were part of the larger, longitudinal twin study of the Leiden Consortium on Individual Development (L-CID). Families with a twin born between 2006 – 2009, living within two hours travel time from Leiden, were recruited through the Dutch municipal registry and received an invitation to participate by post. Parents could show their interest in participation using a reply card. For the larger L-CID study, only same-sex twins were included. Opposite-sex twins were included only in the pilot study. The pilot sample consisted of 20 children between the ages of 7 and 10 (11 boys, M=8.16 years, SD=0.95), including 9 opposite-sex twin pairs. Two additional participants were recruited from a participant data base at Leiden University. Two months after the pilot sample, the test and replication samples were recruited. The test and replication sample consisted of 30 same-sex twin pairs (16 boys, M=8.22 years, SD=0.67), including 7 monozygotic pairs. After data collection, but prior to data analyses, first and second born children (within the twin pair) were randomly assigned to the test and replication sample. For a schematic overview of sample selection see Figure S.1 (2.Supplementary Materials). The Dutch Central Committee on Human Research (CCMO) approved the study and its procedures. Written informed consent was obtained from both parents. All participants were fluent in Dutch, had normal or corrected-to-normal vision, and were screened for MRI contra indications. All anatomical MRI scans were reviewed and cleared by a radiologist from the radiology department of the Leiden University Medical Center (LUMC). No anomalous findings were reported.
Six participants were excluded due to excessive head motion, which was defined as >1 mm movement in >20% of the volumes (one from the pilot sample, two from the test sample and three from the replication sample). The final pilot sample consisted of 19 participants, including 8 twin pairs (10 boys, M=8.18 years, SD=0.97), the final test sample consisted of 28 participants (12 boys, M=8.23 years, SD=0.67) and the final replication sample consisted of 27 participants (12 boys, M=8.28 years, SD=0.65). Demographics of the final samples are listed in Table 1. Participants’ intelligence (IQ) was estimated with the subsets ‘similarities’ and ‘block design’ of the Wechsler Intelligence Scale for Children, third edition (WISC-III; Wechsler, 1997). For all three samples, estimated IQs were in the normal to high range (see Table 1). In all three samples, IQ scores were
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