There is this heise article https://www.heise.de/ct/artikel/Die-Psycho-Tricks-der-App-Entwickler-4547123.html (unfortunatley in German) talking about manipulative mechanisms in mobile apps. He is talking amongst others about snapshat evaluating realtionships with the help of emojis - I was wondering if there are any offical studies or papers talking about how this kind of features in apps makes people addicted to keep using these apps.