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In our study we measured the time needed to complete the task of navigating through different objects in a Pad++ presentation, the total number of hyperlinks followed, and the retention of information after the task was completed. The number of hyperlinks followed is used here as an indirect measurement of user error rates. The independent variable we manipulated was zoom period, or the time needed to move from one object to another within the presentation.
Our hypotheses were as follows:
The rationale for the first hypothesis is provided by the Grossberg et. al. (1976) study presented in "Designing the User Interface." In this study response times were varied over a far greater range than is covered by our treatments of zoom period, and the result is users completed a complex task in the same amount of time by fitting their strategy to the system response time.
The rationale for the second hypothesis is provided by the Barber and Lucas (1983) study, also presented in "Designing the User Interface". This study shows that error rates increase as response time nears zero, as users make hasty decisions. It also shows that users get frustrated and make errors if response times are too slow, but our zoom periods are much shorter than the 12 second point at which the error rate starts to increase again.
Finally, our hypothesis on retention is based on the metaphor of moving through space, rather than jumping instantly to new pages. The working hypothesis is that the spatial information is easier to hold in short-term and working memory. Darken and Sibert (1996) have shown that when users lack cues to help them navigate through large virtual spaces they tend to get lost. Our hypothesis is that animating the motion between hyperlinked objects provides spatial cues that help users retain a sense of where things are in a Pad++ presentation.