Abstract
Using a qualitative monozygotic (MZ) twin differences design we explored whether adolescent MZ twins report discordant peer relationships and, if so, whether they perceive them as causes, consequences or correlates of discordant behaviour. We gathered free-response questionnaire data from 497 families and conducted in-depth telephone interviews with 97 of them. Within this dataset n = 112 families (23% of the sample) described discordant peer relationships. Six categories of discordance were identified (peer victimisation, peer rejection, fewer friends, different friends, different attitudes to friendship and dependence on co-twin). Participants described peer relationship discordance arising as a result of chance occurrences, enhanced vulnerability in one twin or discordant behaviour. Consequences of discordant peer relationships were seen as discordance in self-confidence, future plans, social isolation, mental health and interests. In all cases the twin with worse peer experiences was seen as having a worse outcome. Specific hypotheses are presented.
Highlights
Behavioural genetic studies have confirmed that there are both genetic and environmental influences on human behaviour [1]
Before presenting the results of these analyses it is important to note that the data represent a series of case studies; they can be used as the basis for testable hypotheses about peer relationships as an aspect of non-shared environment (NSE), they do not in themselves speak to direction of effects
A recent MZ differences study identified being bullied as an NSE experience that was predictive of psychiatric dysfunction for environmental (NSE) reasons [33]
Summary
Behavioural genetic studies have confirmed that there are both genetic and environmental influences on human behaviour [1]. An MZ differences design, based on withinpair discordance, can hold constant the effects of genes and many aspects of the family environment, making it possible to develop hypotheses about environmentally mediated relationships between experiences and behaviour. In one study which used two independent samples–one of adoptive and non-adoptive siblings and another of mixed sibling types (including twins)– 70–80% of the total variance in self-reported peer group delinquency was explained by NSE effects [19]. These findings were later replicated with teacher- and observer-report data, offering strong empirical support for Harris’ theory that peer relationships represent a truly environmental influence [20]. We waited to see whether, in line with Judith Rich Harris’ 1998 claim: 1. families would describe discordant peer relationships and, if so, 2. whether they would interpret them as causes (causal hypothesis), consequences (selection hypothesis) or correlates of discordant behaviour
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
