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Contrary to the work presented in [18] and [19], a more complex
spatial assessment task was employed here that required the estimation of
two different metrics as well as their relative ratios. In a 2D visualization
of bars, this task must be performed as a two-stage sequence requiring
short term memory. The 3D visualization of bars provided an alternative,
immediate cue to directly assess these ratios for the slope of imaginary
lines connecting bar ends in relation to the ground.
In this study, no follow-up was done to verify whether subjects
actually pursued this immediate strategy to estimate slope directly.
Therefore, it cannot be ruled out that participants in the study actually used
the same strategy to solve the task as in 2D. Yet, on the other hand, test
participants were asked in the questionnaire which of the two
visualizations they felt most confident with in regard to their performance.
Only three (17%) voted for 2D, whereas the remaining 15 subjects (83%)
felt more confident with the 3D visualization.
Considering, again, that almost half of the population felt visual
discomfort in 3D, these results confirm what appears to be a prevalent
overestimation of the real benefits of three-dimensional visualizations.
It must be assumed that the assessment of the slope of an imaginary 3D
line over a ground plane is ambiguous in a projective display. In providing
strong 3D cues (mainly stereoscopy and motion-parallax) in the proposed
3D visualization, we hoped to alleviate this problem, but there is no
evidence as to how much participants in this study exploited these cues.
Self-assessments of individual 3D capabilities were reliable. Subjects
who rated their spatial skills high, indeed performed better on the tasks,
not only in the 3D part but also in 2D.
Contrary to other research that speaks about the increased 3D and
spatial skills of people who are frequent game players, the opposite was
found in this study. Frequent players did not apparently achieve any
difference in performance in the 3D task compared with non-players.
On a final note, it can be concluded that the results of these studies are in
line with those of a number of previous works in the field of geospatial
visualization which do not point out strong advantages of 3D
visualizations for the type of spatial tasks investigated.
On the other hand, there is ample evidence in the literature that three-
dimensional visualizations are effective for other types of tasks
(interpretation of tree-like graphs), and that dynamic spatial cues in 3D
visualization play a significant role.
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