  Social media platforms use short, highly engaging videos to catch users'
attention. While the short-form video feeds popularized by TikTok are rapidly
spreading to other platforms, we do not yet understand their impact on
cognitive functions. We conducted a between-subjects experiment (N=60)
investigating the impact of engaging with TikTok, Twitter, and YouTube while
performing a Prospective Memory task (i.e., executing a previously planned
action). The study required participants to remember intentions over
interruptions. We found that the TikTok condition significantly degraded the
users' performance in this task. As none of the other conditions (Twitter,
YouTube, no activity) had a similar effect, our results indicate that the
combination of short videos and rapid context-switching impairs intention
recall and execution. We contribute a quantified understanding of the effect of
social media feed format on Prospective Memory and outline consequences for
media technology designers to not harm the users' memory and wellbeing.
