Crystal Smit

Chapter 1 16 is suggested to be critical for the promotion of positive dietary-related behaviors (Salvy et al., 2012). Therefore, the present dissertation explored the potential of using peer influence in interventions, taking into account the role of social norms. Social Network Interventions A state-of-the-art intervention approach that utilizes peer influence in order to promote behavioral change, is the social network intervention (Valente, 2012, 2015). At the heart of this approach lies diffusion of innovations theory, which conceptualizes how new ideas, beliefs, and behaviors are informally diffused through individuals in a social network (Rogers, 2010). During the diffusion process, some individuals lead in influencing their peers’ opinion and beliefs and serve as social models due to their unique and influential position in the social network (Rogers, 2010). These individuals can be deployed to initiate and accelerate the diffusion process of the target behavior in their social networks (Valente & Davis, 1999). Based on this premise, in social network interventions a subset of individuals are selected and trained as influence agents (also referred to in the literature as opinion leaders , peer supporters, peer leaders or champions ; Campbell et al., 2008; Valente & Pumpuang, 2007) to informally diffuse the intended message or behavior in their social network (Valente, 2012). The literature describes several methods of selecting influence agents (e.g., celebrities, self-selection, expert identification, or peer nominations), with the most commonly used method being peer nominations of all members in their social network. Those who have received the most nominations (i.e. the top 10 to 15%) are then selected as influence agents (Valente, 2012; Valente & Pumpuang, 2008). This social network intervention approach has already been applied in the field of public health (Bell, Audrey, Cooper, Noble, & Campbell, 2017; Campbell et al., 2008; Kelly et al., 1991; Sebire et al., 2018; Story, Lytle, Birnbaum, & Perry, 2002; Valente, Hoffman, Ritt-Olson, Lichtman, & Johnson, 2003; Valente et al., 2003; van Woudenberg et al., 2018). An example of particular relevance to the objectives