Maartje Boer

CHAPTER 8 242 (‘How many times per day do you check your smartphone to see whether you have received a message?’), and IM sending (‘How many times per day do you send a message, photo or video via your smartphone?’). Response options ranged from (1) never or less than once to (7) more than 80 times . The questionnaire presented examples of IM, including ‘WhatsApp, Chat, SnapChat, or SMS’. SNS posting was considered the most active SMU activity , followed by IM sending, SNS responding, and SNS liking. This is because SNS posting involves self-broadcasting messages, photos, or videos to a large public audience. IM sending involves sending personalizedmessages, photos, or videos to specific persons or private groups. SNS responding typically involves brief responses to other people’s posts. SNS liking includes one-click feedback on other people’s posts or responses. SNS viewing was considered the most passive SMU activity , followed by IM viewing. This is because SNS viewing involves browsing other people’s posts or reading news feed, whereas IM viewing has a more social component because it involves reading received personalized messages. Social Comparison Social comparison was measured using a newly developed 5-item scale on social comparison during SMU. Specifically, the scale examined upward social comparison during SMU , because upward comparisons are regarded to elicit greater sensitivity to SMU effects than downward or general comparison behaviors (Verduyn et al., 2020). Respondents were asked ‘How often do you have the following thoughts when viewing your peers’ messages, photos, and videos on social network sites?’, followed by: ‘He or she does more fun things than I do’, ‘He or she has more friends than I do’, ‘He or she is more popular than me’, ‘He or she received more ‘likes’ than me’, and ‘He or she looks better than I do’, with responses ranging from (1) never to (5) very often. Cronbach’s alpha was 0.88. Controls We controlled for SMU problems, gender, educational level, and immigrant background. We used the 9-item Social Media Disorder-Scale to assess adolescents’ SMU problems (Boer, Stevens, Finkenauer, Koning, et al., 2021; Van den Eijnden et al., 2016). The items correspond to the nine criteria for