Network interventions can help to achieve behavioural change by inducing peer-pressure in the network. However, inducing peer-pressure without considering the structure of the existing social network may render the intervention ineffective or weaker. In a seven-week school-based field experiment using preadolescents’ physical activity as a proxy for estimating behavioural change, we test the hypothesis that boys’ and girls’ distinct networks are susceptible to different social incentives. We run three different social-rewards schemes, in which classmates’ rewards depend on the physical activity of two friends either reciprocally (directly or indirectly) or collectively. Compared with a random-rewards control, social-rewards schemes have an overall significantly positive effect on physical activity (51.8% increase), with females being more receptive to the direct reciprocity scheme (76.4%) and males to team (collective) rewards (131.5%). Differences in the sex-specific sub-networks can explain these findings. Network interventions adapted to the network-specific characteristics may constitute a powerful tool for behavioural change.
Bibliographical noteFunding Information:
We thank S. Gächter, A. M. Espin, S. Kriemler, F. Exadaktylos, E. Yoeli, E. Woelbert, S. Stoffel and J. Fooken for discussions and feedback. We also thank C. Merletti representing the Ufficio Scolastico Territoriale per la Lombardia for his authorization and ethical approval for this study in schools under his responsibility. We thank P. Benetti from the same office for coordinating communication with all school directors, teachers, parental associations and students’ parents. We finally thank all the school directors and teachers involved, and all the parents and the children who agreed voluntarily to participate in this study (Scuola Primaria “G. Galilei”, Ispra; Scuola Primaria “S. Pellico”, Ranco; Scuola Primaria “G. Pascoli”, Taino; Scuola Primaria “D. Alighieri”, Angera; Scuole Primarie “G. Ungaretti” and “G. Matteotti”, Sesto Calende; Scuola Primaria “D. Alighieri” Golasecca; Scuola Primaria “A. Manzoni” Mercallo; Scuola Primaria “L. Scotti” Laveno; Scuola Primaria” G. de Amicis” Vergiate; Scuola Primaria “G. Wojtyla” Cimbro; Scuola Primaria “S. Tamborini” Varano Borghi; Scuola Primaria “A. Liborio” Comabbio, Scuola Primaria “A. Manzoni” Malgesso). This research was exclusively funded by the European Commission. The supply of the technical equipment (accelerometers) and the contributions of H.B. and E.v.S. were supported by the Medical Research Council (MC_UU_12015/7), and the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence (RES-590-28-0002). Funding from the British Heart Foundation, Department of Health, Economic and Social Research Council, Medical Research Council and the Wellcome Trust, under the auspices of the UK Clinical Research Collaboration is acknowledged. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. Any opinions expressed in this article are those of the authors and not of the European Commission or any other involved institute affiliated by the authors. Data on physical activity and bilateral friendships are provided by the authors upon request.
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