Perceptual complexity of soil-landscape maps: a user evaluation of color organization in legend designs using eye tracking

We compared the ability of two legend designs on a soil-landscape map to efficiently and effectively support map reading tasks with the goal of better understanding how the design choices affect user performance.Developing such knowledge is essential to design effective interfaces for digital earth systems.One of the two legends contained an alphabetical ordering of categories,while the other used a perceptual grouping based on the Munsell color space.We tested the two legends for 4 tasks with 20 experts(in geography-related domains).We analyzed traditional usability metrics and participants’eye movements to identify the possible reasons behind their success and failure in the experimental tasks.Surprisingly,an overwhelming majority of the participants failed to arrive at the correct responses for two of the four tasks,irrespective of the legend design.Furthermore,participants’prior knowledge of soils and map interpretation abilities led to interesting performance differences between the two legend types.We discuss how participant background might have played a role in performance and why some tasks were particularly hard to solve despite participants’relatively high levels of experience in map reading.Based on our observations,we caution soil cartographers to be aware of the perceptual complexity of soil-landscape maps.

Comparative eye-tracking evaluation of scatterplots and parallel coordinates

We investigate task performance and reading characteristics for scatterplots(Cartesian coordinates)and parallel coordinates.In a controlled eye-tracking study,we asked 24 participants to assess the relative distance of points in multidimensional space,depending on the diagram type(parallel coordinates or a horizontal collection of scatterplots),the number of data dimensions(2,4,6,or 8),and the relative distance between points(15%,20%,or 25%).For a given reference point and two target points,we instructed participants to choose the target point that was closer to the reference point in multidimensional space.We present a visual scanning model that describes different strategies to solve this retrieval task for both diagram types,and propose corresponding hypotheses that we test using task completion time,accuracy,and gaze positions as dependent variables.Our results show that scatterplots outperform parallel coordinates significantly in 2 dimensions,however,the task was solved more quickly and more accurately with parallel coordinates in 8 dimensions.The eye-tracking data further shows significant differences between Cartesian and parallel coordinates,as well as between different numbers of dimensions.For parallel coordinates,there is a clear trend toward shorter fixations and longer saccades with increasing number of dimensions.Using an area-of-interest(AOI)based approach,we identify different reading strategies for each diagram type:For parallel coordinates,the participants’gaze frequently jumped back and forth between pairs of axes,while axes were rarely focused on when viewing Cartesian coordinates.We further found that participants’attention is biased:toward the center of the whole plot for parallel coordinates and skewed to the center/left side for Cartesian coordinates.We anticipate that these results may support the design of more effective visualizations for multidimensional data.

Analyzing gaze behavior for text-embellished narrative visualizations under different task scenarios

We conduct an eye tracking study to investigate perception text-embellished narrative visualizations under different task conditions.Study stimuli are data visualizations embellished with text-based elements:annotations,captions,labels,and descriptive text.We consider three common viewing tasks that occur when these types of graphics are viewed:(1)simple observation,(2)active search to answer a query,and(3)information memorization for later recall.The overarching goal is to understand,at a perceptual level,if and how task affects how these visualizations are interacted with.By analyzing collected gaze data and conducting advanced semantic scanpath analysis,we find,at a high level,diverse patterns of gaze behavior:simple observation and information memorization lead to similar optical viewing strategies,while active search significantly diverges,both in regards to which areas of the visualization are focused upon and how often embellishments are interacted with.We discuss study outcomes in the context of embellishing visualizations with text for various usage scenarios.

Legends of the dashboard: an empirical evaluation of split and joint layout designs for geovisual analytics interfaces

Geodashboards are often designed with explanatory elements guiding users.These elements(e.g.legends or annotations)need to be carefully designed to mitigate split attention or information integration issues.In this paper,we report expert interviews followed by a controlled experiment where we compare two interface designs with a focus on the split attention effect:(1)a multiple-legend layout with explanatory elements located next to each view,and(2)a single-legend layout with all explanatory elements gathered in one place.Different legend layouts did not affect the performance,but affected user satisfaction.75%of the participants preferred the multiple-legend layout,and rated it with a higher usability score,mainly attributing this preference to the proximity of legend elements to the view of interest.Eye tracking data strongly and clearly verifies that participants indeed make use of the proximity:With the single-legend,the majority of eye-movement transitions were between the single-legend and the closest view to the legend,whereas with multiple-legend participants have shorter and more frequent legend visits,as well as more transitions between legends and views.Taken together,the design lesson we learned from this experiment can be summarized as‘split the legend elements,but make it close to the explained elements’.