Counting How the Seconds Count: Understanding Algorithm-User Interplay in TikTok via ML-driven Analysis of Video Content

Abstract: Short video streaming systems such as TikTok, Youtube Shorts, Instagram Reels, etc have reached billions of active users. At the core of such systems is a (proprietary) recommendation algorithm which recommends a sequence of videos to each user, in a personalized way. We aim to understand the temporal evolution of recommendations made by these algorithms and the interplay between the recommendations and user experience. While past work has studied recommendation algorithms using textual data (e.g., titles, hashtags, etc.) as well as user studies and interviews, we add a third modality of analysis - automated analysis of the videos themselves. Our content-based analysis framework leverages recent advances in Vision LLMs (VLMs). Together we use this trifecta of methodologies (analysis of user watch history and logs, user studies and interviews, and content-based analysis) to analyze challenging temporal aspects of how well TikTok's recommendation algorithm is received by users, is affected by user interactions, and aligns with user history; as well as how users are sensitive to the order of videos recommended, and how the algorithm's effectiveness itself may be predictable in the future. While it is not our goal to reverse-engineer TikTok's recommendation algorithm, our new findings indicate behavioral aspects that both users and algorithm developers would benefit from.