From Click Modeling to Offline and Off-Policy Evaluation in Carousel Recommendation

Abstract

Carousel interfaces are widely used in modern recommendation systems. Unlike traditional interfaces that present a single ranked list, carousels simultaneously present several ranked lists to the user, as horizontally swipeable rows stacked on top of each other. In this design, the rankings are closely tied to the two-dimensional layout. Consequently, user behavior is shaped not only by item preference, but also by row organization, viewport constraints, and item context. This tight coupling between ranking and presentation complicates the interpretation of user feedback, introducing new challenges for recommendation evaluation. My PhD research aims to address these challenges by rethinking how carousel clicks are modeled and how carousel recommendation policies can be evaluated from logged interaction data. So far, I have studied how users interact with carousel interfaces and developed a click model design framework that prioritizes mathematical relationships between observed variables over latent behavioral assumptions. Building on these results, my ongoing work includes a project using discrete choice models to represent clicks as choices, alongside a project that develops carousel-specific offline metrics. As a next step, I plan to develop off-policy evaluation methods that estimate the performance of recommendation policies from logged interactions. Taken together, the expected contribution of my thesis is a connected body of work that links carousel click modeling with offline and off-policy evaluation, so that carousel recommendation policies can be improved more reliably.