How are searching and reading intertwined during retrieval from hierarchically structured documents?

Effective use of information retrieval systems requires that users know when to-temporarily-cease searching to do some reading and where to start reading. In hierarchically structured documents, users can to some extent interchange searching and reading by entering the text at different levels in the structure. Based on an experiment where 83 subjects solved 20 tasks each, we find that the subjects spend at least one third of their time reading, irrespective of whether the system they use offers browsing and/or querying. The subjects prefer reading the text in chunks that span multiple levels of the structure. As much as 21% of the tasks are solved by subjects who enter the text at a level above the texts containing the answer and rely on reading from there. In relation to queries, multi-level texts are used to extend hits with more detail or, occasionally, more context. Designers should consider how information retrieval systems could exploit document structure to return the best points to support reading, rather than merely hits,