Abstract
In this paper a laboratory experiment is reported which attempted to assess the effect of the metaphor of semi-transparent sheets provided with file tabs, on the accuracy of the user's mental model of the interface. Fifty-six subjects were given two tasks each. Each task consisted of physical manipulation puzzles in which squares had to be moved into a predefined pattern within each of three rectangular, 2D spaces (sheets). In the second task the sheets either seemed semi-transparent sheets stacked on top of each other, the “active”, topmost, squares having brighter and more saturated colors than the “inactive” ones, or seemed completely transparent (all squares having the same brightness and saturation). Furthermore, the sheets in this task either seemed to have file tabs to indicate which sheet was on top (file tab metaphor) or had the same functionality with a more abstract appearance. The correctness and efficiency of all actions undertaken during the experiment were recorded. Results show that the presence of both metaphors (irrespective of the presence of the other metaphor) during the second task facilitated an accurate mental model. However, the two metaphors combined into the composite metaphor of semi-transparent sheets provided with file tabs only in an additive (non-interactive) way. Finally, it was found that working without the file tab metaphor on the second task was not facilitated by the memory of having worked with this metaphor on the first task (which was a simple variation of the second task). Implications of this study for the theory and practice of designing interface metaphors are discussed.
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