Hierarchical histories for hypertext navigation: a pilot study of individual differences

Two hypermedia navigation aids are virtually ubiquitous - the history list, and the graphical overview. However, it can be argued that there is an increasing need for a half-way house between the linear record of the individual's session, and the hierarchical or network representation of abstract document structure. We are therefore investigating 'hierarchical histories': one particular approach to this enables backtracking to be based on the structure of the user's dialogue with hypermedia system. We believe that such 'discourse-structured backtracking' (DSB) avoids various difficulties that have been pointed out in the literature, and improves a hypertext system's usability. To test this, we have implemented DSB in Emacs Info, and run some simple experiments; the pilot results confirm the importance to navigation of individual differences in cognitive style. In particular, we believe that DSB may help alleviate the navigational problems suffered by users with poorer spatial visualisation skills.