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Disentangle personalization from customization in search engine results

Determine the specific user-behavior-based factors that web search engines (e.g., DuckDuckGo, Google, and Yahoo) use to tailor ranked search results to individual users, and establish a clear methodology to distinguish personalization effects from customization effects arising from non-personal features such as location and language, in order to assess their respective impacts on the content users see.

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Background

The paper highlights that search engines employ various criteria to generate results, yet the precise factors used to tailor content to individual users remain opaque. This opacity is especially problematic when the tailoring is based on user behaviour, which can have significant societal impacts.

The authors note that it is often impossible to tell whether differences in results stem from personalization (user-specific tailoring) or customization (contextual factors like location or language). The paper proposes an audit methodology but explicitly acknowledges the underlying uncertainty about what factors contribute to tailoring.

References

Still, the factors used to tailor results to a specific user, remain uncertain, despite their potentially large impacts . In fact, it is often impossible to distinguish if differences are due to personalization, here defined as search results curated particularly for a user in question, considering the user's tastes and specific profile or to customization, which, may result from differences in less personal features, such as location or language.

— Digital Gatekeeping: An Audit of Search Engine Results shows tailoring of queries on the Israel-Palestine Conflict (2502.04266 - Damião et al., 6 Feb 2025) in Section 2, Background and Related Work