Esther Mertens

10 | Chapter 1 General introduction Skills and struggles in the intrapersonal and interpersonal domain are important predictors of adolescents’ psychosocial wellbeing and their development into adulthood (Barber, 2005; Shek & Leung, 2016). The intrapersonal domain refers to the ability to manage one’s own feelings, emotions, and attitudes about the self (Barber, 2005). This domain concerns the subjective processing of behaviors, thoughts, and emotions pertained by the individual self (Dufner, Gebauer, Sedikides, & Denissen, 2019; Finkel & Vohs, 2006). Evaluating and regulating one’s own inner world and experiences can facilitate positive personal functioning (e.g., psychological wellbeing and resilience), whereas difficulties in this process can create psychological problems (e.g., internalizing behavior; Dufner et al., 2019). The interpersonal domain refers to the ability to build and maintain positive relationships with others, to understand social situations, roles and norms, and to respond appropriately (Pellegrino & Hilton, 2012; Shek & Leung, 2016). By planning one’s own behavior and predicting the behavior of others one can act in a socially appealing way, such as building positive interpersonal relations, or in a more destructive way, such as behaving aggressively or bullying (Finkel & Vohs, 2006). Both domains bidirectionally influence each other. For instance, how individuals view themselves can influence the way they approach social interactions and vice versa (Finkel & Vohs, 2006). Although the domains are intertwined, they are regarded as distinct domains. While the intrapersonal domain reflects subjective personal functioning, the interpersonal domain reflects social functioning (Dufner et al., 2019). Not only do factor and profile analyses support this distinction (Gilman & Anderman, 2006; Park, Tsukayama, Goodwin, Patrick, & Duckworth, 2017), the two domains are also related to different outcomes. For instance, the intrapersonal domain predicts academic achievement, whereas the interpersonal domain predicts positive peer relations (Park et al., 2017). Individuals can develop competencies in both domains by mastering relevant cognitive, affective, and social skills such as the ability to identify emotions (intrapersonal domain), to take perspective, and to help others (interpersonal domain; Durlak, Weissberg, Dymnicki, & Taylor, 2011; Hughes, Kratsiotis, Niven, & Holman, 2020). When students struggle with mastery of (some of) these skills, individuals have an increased risk of developing problems in the intrapersonal domain, such as internalizing behavior (White, Jarrett, & Ollendick, 2013), as well as in the interpersonal domain, such as externalizing behavior (Modecki, Zimmer-Gembeck, & Guerrà, 2017). Competencies within both the intra- and interpersonal domain are particularly pivotal during adolescence for two main reasons. First, adolescents are consolidating their own identity (Barber, 2005). To foster the process of identity formation, adolescents need to be able to identify their strengths, limitations and values, and need to have a positive attitude about the self (Barber, 2005; Shek & Leung, 2016). Positive and negative feelings and emotions take a central role in the process of