Improving Exploration of Topic Hierarchies: Comparative Testing of Simplified Library of Congress Subject Heading Structures

Many large digital collections are organized by sorting their items into topics and arranging these topics hierarchically, such as those displayed in a tree view. The resulting information organization structures mitigate some of the challenges of searching digital information realms; however, the topic hierarchies are often large and complex, and thus difficult to navigate. Automated techniques have been shown to produce significantly smaller, simplified versions of existing topic hierarchies while preserving access to the majority of the collection, but these simplified topic hierarchies have never been tested with human participants, and so it is not clear what effect simplification would have on the exploration and use of such structures for browsing and retrieval. This study partly addresses this gap by performing a comparative test with three groups of university students (N=62) performing ten topic hierarchy exploration tasks using one of three versions of the Library of Congress Subject Headings (LCSH) hierarchy: 1) the original LCSH hierarchy, acting as a baseline, 2) a shallower version of 1), and 3) a narrower version of 2). A quantitative analysis of measures of accuracy, time, and browsing shows that participants using the simplified trees were significantly more accurate and faster than those using the unmodified tree, and the narrower, balanced tree was also faster than the shallower tree. These results show that automated topic hierarchy simplification can facilitate the use of such hierarchies, which has implications for the development of information organization theory and human-information interaction techniques for similar information structures.