Abstract: ［Purpose/Significance］This study aims to explore communication contents and patterns while people are searching collaboratively, and tries to understand the characteristics of collaborative information search. ［Design/Methodology］The experiment was designed based on the book interactive retrieval platform called CLEF-Social Book Search. Eighteen collaboration participants were recruited to laboratory to complete two different types of book search tasks. Users’ interactions with the system during their search were recorded through the backend server. Communication contents of collaborative searchers were recorded, coded and analyzed.Then the contents’ characteristics and communication patterns were concluded. Exploration was conducted with the consideration of the task and cognitive type combination, logs of interactive search behavior recorded by server and search experience collected by questionnaire. ［Findings/Conclusion］(1)Communication contents: Collaborative searchers mainly discuss about the understanding and judgement of books and task plans. They have more discussion about task understanding in the goal-oriented task than in the open-ended task. Searchers of the same cognitive style communicate more about operations than searchers of different cognitive styles, while less about judgements. (2)Communication patterns: Communication patterns can be divided into three groups including understanding and judging group, judging-orientated group and balanced communicating group according to the proportion of discussed contents. Judging-oriented group are relatively more satisfied with the results than the other two groups.［Originality/Value］It has been found that collaborative searchers need to discuss about collaborative focuses with their partners during the search, which the system should significantly facilitate. This study helps understand more about collaborative search by analyzing communication contents and patterns, which may provide inspiration for collaborative search system design. In addition, the coding system of collaborative search communication contents offers reference for other collaborative communication research.

Key words: Collaborative information search, Communication mode, Collaborative search strategy, Information behavior, User experiment