Although current literature has extensively discussed media literacy processes, few theories exist explaining the role of social media literacy. Social media is used daily by a substantial number of young people and may exert an important influence on its users' wellbeings. Considering media literacy, media effects, social psychology, interpersonal communication and educational literature, a novel theoretical framework called the Social Media Literacy (SMILE) model is introduced. This framework was formulated to explain 1) how to conceptualize social media literacy, 2) how social media literacy can change the dynamics between social media and its users and 3) how participatory mediation processes result into social media literacy. The SMILE-model is illustrated against the background of the social media positivity bias. Ultimately, the newly developed guiding framework aims to stimulate more theory-driven research into the scholarly understanding of social media literacy in well-being. Such insights may especially be useful for research in the field of children, adolescents and the media.

The present study conceptualized and developed new measurement instruments to assess adolescents' a) exposure to, b) liking and c) posting of positive content on social media. By means of an integrative review of the literature, six focus group and 14 indepth interviews, nineteen items were developed for each scale. Based on a crosssectional study among 294 adolescents, EFA and CFA extracted two valid and reliable factors for exposure to positive social media content, one valid and reliable factor for liking positive social media content, and three valid and reliable factors for posting positive social media content. A short version of these three (multifactorial) scales was created and administered in a two-wave panel study among 1419 adolescents and in a cross-sectional study among 493 late adolescents. Test-retest reliability, structural validity, construct validity and full metric invariance across age and gender were established for all short scales, except for the posting scale for which only partial metric invariance was achieved across gender.

Despite voiced concerns about sexual online risk behaviors related to mobile dating, little is known about the relation between mobile dating and sexting. The current crosssectional study (N = 286) examined the relations between the use of geo-social dating apps and emerging adults' willingness to sext with a dating app match. By drawing on the prototype willingness model, both a reasoned path and a social reaction path are proposed to explain this link. As for the reasoned path, a structural equation model showed that more frequent dating app usage positively related to norm beliefs about peers' sexting behaviors with unknown dating app matches (i.e., descriptive norms), norm beliefs about peers' approval of sexting with matches (i.e., subjective norms), and negatively related to perceptions of danger to sext with matches (i.e., risk attitude). In turn, descriptive norms positively and risk attitudes negatively associated to individuals' own willingness to sext with someone they had met through a dating app. As for the social reaction path, it was found that more frequent dating app usage positively related to emerging adults' favorable evaluations of a prototype person who sexts with unknown dating app matches (i.e., prototype perceptions). The analyses further revealed that such prototype perceptions positively linked with emerging adults' own willingness to sext with a match. These results were similar among women and men and help explain why individuals may be willing to engage in sexting behavior with unknown others.