Does Personalization Benefit Everyone in the Same Way? Multilingual Search Personalization for English vs. Non-English Users M. Rami Ghorab, Séamus Lawless, Alexander O’Connor, Vincent Wade Centre for Next Generation Localisation, Knowledge & Data Engineering Group, School of Computer Science & Statistics, Trinity College Dublin, Ireland [rami.ghorab, seamus.lawless, alex.oconnor, vincent.wade]@scss.tcd.ie Abstract. The web community is witnessing an increase in the amount of avail- able multilingual content and the number of multilingual web users. With this variety, personalized search systems are needed to connect people with relevant content, regardless of the language in which the content is provided, and taking into consideration the user’s language capabilities and preferences. Therefore, search personalization algorithms should be developed with the aspect of multi- linguality in mind, part of which involves understanding the effect of personali- zation algorithms on the user’s search experience. This leads to an important question: given that users come from different linguistic backgrounds and have different language preferences, would personalization benefit all search users in the same way? This paper addresses this question by conducting an experiment to: (1) evaluate the effectiveness of the multilingual personalization algorithms (multilingual user modeling and multilingual result adaptation); and (2) deter- mine whether multilingual personalization algorithms achieve the same degree of effectiveness for users who have different language preferences. Keywords: Personalization, Multilingual Search, Information Access. 1 Introduction The web is becoming increasingly multilingual, with respect to both content 1 and users 2 . Nearly half of the content available on the web is provided in languages other than English, such as Russian (6%), Spanish (5%), Chinese (4%), Japanese (4%), and Arabic (3%). The best answer to a user's query may not necessarily be available in his/her own language, but may reside in the diverse, multilingual corpora of the web. This calls for solutions that not only assist the users in finding relevant information, 1 http://en.wikipedia.org/wiki/Languages_used_on_the_Internet 2 http://www.internetworldstats.com/