Google Research

Diverse User Preference Elicitation with Multi-Armed Bandits

Proceedings of the ACM international Conference on Web Search and Data Mining (WSDM) (2021) (to appear)


Personalized recommender systems rely on knowledge of user preferences to produce recommendations. While those preferences are often obtained from past user interactions with the recommendation catalog, in some situations such observations are insufficient or unavailable. The most widely studied case is with new users, although other similar situations arise where explicit preference elicitation is valuable. At the same time, a seemingly disparate challenge is that there is a well known popularity bias in many algorithmic approaches to recommender systems. The most common way of addressing this challenge is diversification, which tends to be applied to the output of a recommender algorithm, prior to items being presented to users.

We tie these two problems together, showing a tight relationship. Our results show that popularity bias in preference elicitation contributes to popularity bias in recommendation. In particular, most elicitation methods directly optimize only for the relevance of recommendations that would result from collected preferences. This focus on recommendation accuracy biases the preferences collected. We demonstrate how diversification can instead be applied directly at elicitation time. Our model diversifies the preferences elicited using Multi-Armed Bandits, a classical exploration-exploitation framework from reinforcement learning. This leads to a broader understanding of users' preferences, and improved diversity and serendipity of recommendations, without necessitating post-hoc debiasing corrections.

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