The influence of node sequence and extraneous load induced by graphical overviews on hypertext learning

The effects of four hypertext learning environments with a hierarchical graphical overview were studied on the coherence of the node sequence, extraneous load and comprehension. Navigation patterns were influenced by the type of overview provided (i.e., dynamic, static) and whether navigation was restricted (i.e., restricted, non-restricted). It was hypothesised that redundant use of the overview for inducing a high-coherence reading sequence would result in high extraneous load and low comprehension. Coherence was higher in the dynamic than in the static conditions. Coherence was also higher in the restricted than in the non-restricted conditions. Mental effort as a measure of extraneous load was higher at the end than at the beginning of the learning phase, especially in the dynamic restricted and the static non-restricted conditions, although there was no significant interaction. Comprehension was lowest in the dynamic restricted condition and highest in the dynamic non-restricted and static restricted conditions. Low comprehension in the dynamic restricted condition indicates that overviews can become redundant for reading sequence coherence, negatively impacting comprehension. The evidence suggests that severe restriction of navigation paths should be avoided and that continuous use of overviews such as in dynamic overviews may be detrimental to learning. In a hypertext environment, the user must navigate between pieces of linked information (i.e., nodes). Each node contains discrete pieces of information and is linked to one or more other nodes, resulting in a non-linear organisation of content (Conklin, 1987). The way in which information is retrieved from hypertext is influenced by the mental model formed of the interface features of hypertext (Marchionini & Shneiderman, 1988). Learning in such environments requires building a mental representation of the structural features of the environment, and at the same time comprehending the content (Schnotz & Heiß, 2009). Comprehension of text based materials involves building mental representations of the text content which is gradually integrated into the existing knowledge structures of the learner, forming a situation model In hypertext environments, building mental representation of the environment's content which meaningfully incorporates the different pieces of information presented at different hypertext nodes are required for successful comprehension (Chalmers, 2003). This process of comprehension, however, is impeded by interruptions in the reading process, which can be a consequence of the elevated navigation requirements associated with the structural characteristics of hypertext. The navigation requirements include having to remember the route to the nodes already visited along with the content displayed on those …